Last week, Alto Cycling published a rim brake performance test showing eight different brand’s rims subjected to consistent rim brake pressure up to the point of failure. Not surprisingly, it generated a lot of comments. And a big response from several of the brands tested. And we do mean big, but it’s interesting reading. Here are reactions and comments from Boyd Cycling, ENVE and Mavic. We also asked Alto Cycling to provide a few additional thoughts and clarifications, which are included.

WHAT WAS WRONG WITH THE TEST?

BOYD: Let’s go back to fundamentals. Braking is about dissipating kinetic energy through friction to stop the bike. In theory, this is what our competitor’s test is trying to drive at. You need to remove energy through braking, and the heat generated can blow apart a wheel. The better a rim surface is at stopping (and they vary a lot from manufacturer to manufacturer) the less braking you will need to do get the bike to stop. So, in theory, if you had a really slippery rim surface, you could hold a brake lever at a given pressure for ever and never get enough friction to generate any heat buildup at all.  But is that a wheel you really want to point down a mountain? This data point was not included in the test though the amount of kinetic energy asked of the tester’s rims was less than all others as it rotated at 1mph faster than all other rims included in the test, drawing the conclusion of having a very slippery brake track.

Boyd basically recreated the Alto test on professional equipment used by a lot of bicycle wheel testing labs. The video shows how braking force and temperature starts dropping. The image below shows the heat graph over time. Note where pads will start to glaze over and leave more residue on the rim, which produces less friction, and then the temperature starts to fall, too. Boyd says a better test is one that uses higher braking force and brings the rim to a complete stop repeatedly because it more closely resembles what you’re actually doing coming down a mountain. Using their 44mm carbon clincher and Black Prince pads, 7lbs of pressure at the brake lever at a constant 15km/h wheel speed, their rim lasted a full 20 minutes with no failure. Feel free to fast forward through the middle. The weird picture-in-picture at the end is showing the two different cameras to show both the wheel and screen. As for why Alto’s test showed completely different results? That’s a mystery to all of us.

boyd cycling carbon rim brake heat management test proves their rims are stable
Results of Boyd’s 20 minute constant braking test.

Conversely, if you have a better stopping rim surface, the same lever force over the same period of time will produce much more heat. However, with the forces that were outlined in the test, a rider would simply come to a stop (well before any heat damage occurred). If you had a large rider, strapped on a weighted backpack, grabbed only the rear brake, and continued to pedal down a very steep hill, then it would be possible to continue riding with the brake force (and generate the heat damage illustrated in that test. But those aren’t real world conditions).

The information needed to really to determine safety is a temperature measurement at time of failure. This is a much better indicator of a rim’s resistance to heat failure.  Running a braking load for a period of time at a force that would cause any rider to stop is completely irrelevant to a rim’s safety.

enve carbon rim brake testing equipment and procedure ensures proper heat management and road bike rim brake performance

ENVE: Their rim doesn’t have any texture, but from our testing, we’ve established that our textured brake track requires 30% less lever force to develop the same amount of stopping power. This is compared to our previous textured braking surface. Compared to a completely smooth brake track… We don’t really know how much more force would be required to achieve the same braking power. So in this Alto test, ENVE’s rim could theoretically have been tested at a minimum 30% more aggressively than any of the others without texture.

Then there is the issue with pads… You cannot generalize or underestimate the value of the brake pad. I get the desire to normalize the test and focus on the carbon structure itself, but as many commentators pointed out, we develop rims and pads to work in harmony for best results. Pad compound is something we’ve spent years and years developing because it absolutely matters for performance and safety. The pads we’ve developed were done in conjunction with our latest textured surface to provide the best balance between heat management, wet and dry performance, modulation, initial bite, and longevity. This of course doesn’t take into consideration the level of refinement an ENVE rim must also receive to ensure impact durability, stiffness, ride quality, etc… There are certainly resin systems that are really great at managing heat, but they often require compromising on durability, weight, longevity, etc…

The ENVE brake track test has evolved over the years as we’ve made improvements to our design, materials, and processes, we’ve had to increase the power level by nearly 50% to produce a rim failure when testing our latest rims. Our test is more complex than simply fixing a lever force and running a motor. The braking force is constantly being adjusted to produce a consistent and specific wattage throughout the test. This is required because as you are aware as things get hotter, they tend to soften/wear/glaze, so the force being applied at the brakes needs to be adjusted constantly. Essentially, the ENVE brake track test is dynamic and the main objective is to maintain a constant power output. This is potentially a major flaw with the Alto test. If they are simply testing to a lever force, the wattage is not constant. In addition to temperature on the outside, we’re also measuring/monitoring temperature inside the rim, dimensional changes in the wheel and tire pressure.

Mavic carbon clinchers have some of the best rim brake stopping power we've tested
Mavic’s yellow brake pads put off a lot of dust, but work with their laser rim surface treatment to create some of the best stopping power we’ve tested.

MAVIC: First of all, and probably the most obvious, the fact that they are not using the pads that each manufacturer recommends is a big issue. We chose the pads that we send with (and recommend as a replacement for) our wheels because it is the best option to meet our performance, safety and durability standards. Using a different pad will change the effect on our rim in terms of how it generates heat. Indeed, we have tested the Black Prince pad with our wheels and even if there is an improvement in braking performance (this is subjective for many reasons) the door is opened for bigger issues – shorter pad life, higher heat in the rims and reduced life of the rim itself. So, as you can see for not just us, but the others as well, there are real performance characteristics that come with the recommended pad and by not using those you are absolutely NOT establishing a level playing field.

Further on the point above, we can now discuss the braking surface. As I just mentioned above, there are performance characteristics that come with the combination of pad / rim used. What we can say is that the Alto rim has very little, if any, texture on the braking surface. So, you can use any pad you like – heck, you could use SOAP – and there will be less heat in those rims. We are 100% sure that if we sent our Cosmic Pro Carbon SL UST rim to them, without the laser treatment we apply to our braking surface, that we would match or surpass their benchmark. So, as the interface between their rim and pad has less friction … there is absolutely less heat and thus, the wheel can run longer before there is damage.

mavic pro carbon sl cosmic and ksyrium road bike carbon clincher wheels first impressions ride review
A laser etched braking surface provides more friction for better bite.

So, the test doesn’t take into account braking efficiency. Meaning, if the braking efficiency is very bad, the pad will just slide on the rim without creating as much friction or resistance (as a more efficient braking system would). Hence, there is not as much heat. When the braking is more efficient, there is more friction, so more resistance and so of course, more heat. All this means it is more open to damage or failure at extreme temperatures. In terms of temps … based on our experience the max temps you might experience in “real life” are around 200º Celsius. (Ed. Check out some of Mavic’s carbon rim brake design in this post and our test impressions here.)

Next, let’s discuss the power delivery. There are many peculiarities with this part of the test. They mention the motor is set at 1200w and the force on the brakes remains consistent at 7lbs (for phase 1). However, when you look at the speed of all of the wheels, including Alto, it doesn’t add up. In our testing, we have seen up to a 50% change in speed depending on the braking surface being tested — we have even seen these big differences between some of the exact wheels they used in their test. So, with a wheel that has an aggressive / high performing braking surface – like the Enve, Mavic or Zipp – there should have been a much bigger difference in the speed if the motor was staying consistent at 1200w. Further, even if it WAS staying consistent at 1200w it creates, yet again, an unfair playing field. A rim with a high performing brake track will generate more heat when compared to a rim with a poor (or no) braking surface treatment and will of course reach a failure quicker. The issue is that in the real world that wheel would have adequately braked, or even stopped, well before failure.

Mavic performs lab testing of braking efficiency before sending their test pilots down the Ventoux for real world testing
Mavic performs lab testing of braking efficiency before sending their test pilots down the Ventoux for real world testing.

Another point regarding speed of the Alto wheel between phase 1 and phase 2 should be mentioned. There is nearly no difference in the speed between the two tests even though there is around 30% more braking force being applied (7lb -> 9lb). Our engineers say that this is simply not possible. The speed should be something around 16mph in phase 2.

Braking power – again, there is a flaw here. There is a weight being applied to a lever which is then putting the pad onto the rim. Again, this is simply not accurate. In order to have a reliable test the pressure should be applied mechanically to the pad and not through a lever and cable with a free hanging weight. Further, it is not effective to apply equal braking force when testing different wheels. In our test, and those you’ll find from other brands I’m sure, we maintain a motor at 600w-700w and adjust the braking force based on the resistance on the motor. This completely levels the playing field for the brake surface treatment. Slicker surface means more braking force because there is less resistance on the motor. More aggressive braking surface means less braking force because of more resistance on the motor. I hope that you can see that this easily points out how they have created a very biased test. Their wheels have little or no brake surface treatment so not only will their wheels have inferior real-world performance compared to us, and others in the test, but their wheels do not have the appropriate braking force on the rim to show how their rim reacts when all of the wheels are tested fairly.

Mavic’s full carbon clinchers were a long time coming, but this graphic shows the three main forces a rim has to deal with.

Now, let’s talk about the heat measurement. In the test Spark was using infrared to measure the heat on the braking surface. Not only is that a poor place to measure the heat, infrared is incredibly unreliable and inconsistent. In testing our wheels, we measure the temperature on the inside of the rim, at the top of the rim hook, using accurate and intricate methods that are exponentially more reliable and consistent than infrared. Our carbon clincher wheels are required to reach or pass a temperature of 200° C (392° F), which is well beyond any real-world circumstance. Further, as we can see by the max temperature they show for our wheel in the test, it is far from our benchmark. Based on the level and frequency of our testing we are 100% sure that there is an issue with their temperature measurement.

Regarding the 34 second cooling time in Phase 1 for the Alto wheel, this is completely impossible and there is no explanation that this can be accurate. When you look at the drastic difference between the Alto wheel and the nearest “competitor” it should automatically tell you that there is a flaw in the measuring. You might argue that Alto is using a proprietary carbon and / or resin to achieve this but again, that is simply not possible. How could it be that they have found a material, or mixture, that is that far advanced when compared to the brands in the test? Do those materials exist? Absolutely … but using them in an application like this the wheels would be astronomically expensive and simply not viable.

WHAT DO THOSE NUMBERS REALLY MEAN?

alto cycling carbon rim brake heat tolerance test results showing comparison between bontrager boyd enve fse zipp roval and mavic carbon rims

BOYD: Resin is the glue that holds carbon together, and when it softens that is what can cause the damage to the rims. When we looked at the results from the published test, we saw that the Boyd 60mm clincher rim was able to reach a higher temperature than any other rim. We also saw that our temperature rose quickly compared to the other rims (under admitted non-real world conditions). We can draw a conclusion from this that the braking performance of our rims was amongst the best out there, and the temperature rating was amongst the best out there. This is on par with what we experience in both lab and real world situations with our test riders and professional athletes who race on the wheels. We work with a professional criterium focused cycling team and even in rainy criteriums the team prefers to ride carbon wheels compared to alloy.

With the resin, we partnered with a manufacturer who actually produces their own resin in house. Versus ordering large rolls of pre-impregnated carbon fiber that has to sit in large freezers for months on end, our carbon manufacturer makes the resin, takes carbon from raw strands, and produces their own pre-preg. All carbon fiber goes from being made into a sheet of pre-preg to a finished product within a week.

WHY ISN’T THERE AN INDUSTRY STANDARD FOR BRAKING PERFORMANCE?

enve carbon rim brake testing equipment and procedure ensures proper heat management and road bike rim brake performance

ENVE: The reality as I see it is that we, along with Zipp, Mavic, and whomever else, have spent oodles of money, time, resources to develop our brake track tests. So put us all in a room together to establish an “industry standard” test is simply highly unlikely. You could say well, don’t you care enough about the safety of consumers that they should all have access to safe rims? Well of course they should, but is it ENVE’s or Zipp’s responsibility to spend all the money, do all the work, and then give our technology to a competitor? At ENVE, we own our responsibility to ensure our customers have a safe product. Ultimately, consumers vote with their wallets. We’ve continued to grow over the years in terms of road market share and it’s not because we make an unsafe product.

I think the reaction we had to this test was more related to the assumption of guilt that it placed on our brand. Like a good old fashion witch hunt. Call them a witch, and you must be a witch. This test is no different than throwing someone in a lake to prove they are a witch.

The reality for ENVE is that this hasn’t been a conversation for us for some years now. As far as we’re concerned, we’ve solved this problem given we’ve had zero returns for heat damage on our latest rims. If a consumer on older rims has an issue, their rim is replaced with the latest technology.

WHAT’S ALTO’S TAKE ON THE FRICTION ISSUE?

2018 Alto Cycling hookless carbon rims are designed for high pressure road bike tires
Alto’s new hookless, tubeless carbon wheels come in disc brake versions, too, just in case you’re over all this.

BIKERUMOR: Do your rims have adequate friction to produce the stopping power that cyclists will want?

ALTO: Of course. All of the rims ran between 19.4 and 20.3 mph during phase 1 for the first 3-5 minutes. After 5 minutes, you’ll notice that the Alto rims speed up. This is because the pads were over 200ºF for so long, they begin to gloss over and lose power. This is a function of the pad and not the rim, and would happen on all of the rims if they were able to get to this point without failing. You’ll notice it happening at the end of the Zipp test. Also check out the phase 2 Alto test and you will see that the rim is running slower than most others, around 19.3mph. This is with 9lbs of lever load instead of 7lbs. So what does that mean? The average grip strength of an adult is 100lbs, which is what you would apply during panic braking. If you are slowing down and you need more power, going from 7lbs to 9lbs isn’t even a noticeable difference. From a subjective “ride test” standpoint, the braking power of all of the rims in this test will feel identical. The difference that you’re seeing in the test is literally only measurable in the lab, but isn’t a large enough difference that anyone would be able to feel it.

BIKERUMOR: If so, how do they provide the stopping power without producing the same heat or resin softening as the others?

ALTO: It all comes down to heat dissipation. As I mentioned above, in phase 2 you can see identical stopping power (on a rim that was already tested for 20min in phase 1) with the Alto rim and you still get significantly better heat dissipation. This is for two reasons: resin quality and construction process. The resin contains multiple additives that allow it to flow more readily through the carbon matrix, allow us to use less of it while better filling any voids. It also has better conductive properties, and an aerospace grade glass temperature that keeps the resin from beginning to soften well above the temperatures that you would see under brake loads. For the construction process, we are filament winding the brake track to provide more compaction and an even tighter matrix. Instead of laying up pre-preg plies by hand, we use a machine to pull and wrap the fibers, keeping them taught as they are laid down. Both of these processes result in a composite that is extremely compact with zero filler material and voids. That means that when heat is transferring through the material, it isn’t hitting air pockets, wrinkles, and voids where is can build and cause critical failure modes. The conductive and heat dissipation properties of our new rim are simply better than anyone else’s.

BIKERUMOR: Do you recommend a specific brake pad for those rims?

ALTO: Nope! We send Black Prince pads with every wheel set because you get great power and modulation with them. But you can use any carbon pad with our wheels. It will not void the 5 year warranty and there isn’t one on earth that would damage them.

WHAT’S THE TAKEAWAY? ARE YOUR CARBON RIMS SAFE?

From our (Bikerumor’s) standpoint, the test was interesting if only to see what happens when a rim overheats. To be fair, Alto made public all of the parameters and put everyone through the same test. But as the brands here have explained, the results don’t necessarily reflect real world conditions. We see the real value as simply being a conversation starter and an opportunity to learn.

ENVE: The reality is that since year one (ten years ago now), we’ve been pushing to develop not only safe, but bombproof braking on carbon. Today we are at a point where what used to be our most common reason for a rim warranty is now non-existent. We literally haven’t had a heat related warranty on any of our wheels that are using our latest materials, processes, and resin systems.

Finally, if you’re starting a wheel company, and find that your wheels are testing 10x better than every leading wheel manufacturers’, with generally good reputations for producing high performance wheels that are also safe, maybe you should ask yourself, “what’s the matter with my test.” There are certainly some brands who are behind the times in terms of braking performance and unfortunately they’ll have to figure it out just like we’ve had to do. The real world results are certainly backing up our lab results and indicating that for ENVE’s consumers, heat damage to brake tracks is a thing of the past.

In summary, regardless of this test and the questionable protocol, we have 100% confidence in our latest carbon brake track technology. The texture is meaningful and for this reason: Given the higher amount of friction and initial “bite” you get a feeling closer to that of disc brakes. Riders then have a more tactile braking feel. Lost is that terrifying feeling that accompanies most smooth carbon braking surfaces where you aren’t sure you’re actually slowing down or braking at all despite your death grip on the lever. Ultimately, our brake track texture results in less contact time between pad and rims and therefore better braking performance.

Starting at about 4:15, the video above shows Mavic’s brake dragging descent test on their “Ventoux Test”. This test puts a 220lb (100kg) rider on the bike, then they ride down the steepest 10km of the Ventoux decent (avg ~10% gradient) with the ear brake engaged for the duration of the test. All of their carbon wheels must pass this test. The first part of the video shows some of their testing and measurement equipment.

MAVIC: I would argue that we have the most stringent testing methods in the world for bicycle wheels and it is not a topic we take lightly. Consumers need to know that this test does nothing but show a biased test that was run in a way that the only outcome would be that the Alto wheel performed better than some of the best wheels in the world.

I am not at all criticizing their motives – I have to believe that their intentions where noble – but this was simply a failure in terms of offering consumers reliable information in terms of making an educated and confident purchase. I am more than surprised that when they saw the results that they didn’t question their testing method. It is unfathomable that a wheel company, that has only existed for less than five years, could suddenly have a wheel that performs so dramatically better than the others in the test.

Finally, I would like to add that as a brand that has made some of the best wheels in the world for more than a century, we are 100% sure that our carbon clinchers are reliable and safe. We do not have the conversation about safety in carbon clinchers like the industry has in the past because we are totally confident in our research, engineering, development and testing. Now that we have added UST rim technology to our road range, we are also confident that we have the very best carbon clinchers available in the world. They perfectly balance performance and reliability and are the only standard for having all of the benefits of a tubeless system that is also user friendly. I hope that you can share that sentiment with your readers to ensure that they are hearing from the other brands in the same way that they have now heard from Alto.

how do carbon rim manufacturers test their braking performance claims
The JTM Technology rim testing machine used in Boyd’s test is a standard for rim manufacturers.

BOYD: Heat is only one thing to talk about, but there are so many aspects to focus on rim and wheel development. Recently, the UCI has developed a test that wheels need to pass in order to be used in the highest level of competition. That test involves dropping a known load from a known height to calculate the impact in joules of force. The UCI sets this at 40 joules of force to pass the testing. It is well know that as you increase the temperature rating of the resins, that brittleness of the rim increases. Zipp, when they developed the Firecrest series talked about how hard it was to find a resin that could handle the high temperatures, but also be suitable for the impact demands of riding a bicycle wheel. You don’t want to be going down a mountain, hit a pothole, and have a rim shatter under you.

As part of having a great relationship with our manufacturer we were able to develop a resin that can withstand temperatures of 205 degrees Celsius before failure. This is over twice the temperature to boil water. Impact strength and ensuring the rim did not become too brittle was also key. We were able to work with them to develop a high temperature resin that can withstand multiple impacts at almost 2.5 times the UCI testing protocol!

Further Reading:

One of the engineers that does CFD work for Boyd Cycling wrote a very detailed post evaluating the Alto experiment from an engineering point of view. Geek out on that, here.

Huge thanks to ENVE, Boyd, Mavic and Alto for their responses, photos and time!

103 COMMENTS

  1. Ugh, my head hurts. Keep your overpriced carbon rims, my sub-$300 aluminum wheels have been not melting down mountains for the last 5 years. Hell, they’re still true too!

  2. I’m happy that we’ve created a dialogue! That’s what it’s all about. I’d like to respond to a few of the points in the article in order to clarify things:

    1. You cannot deny the first law of thermodynamics, no matter what. The energy dissipated by each rim is identical: 1200 watts. Simply increasing the coefficient of friction on a brake track does not create energy — it slows down the wheel. You must consider the kinetic energy of the rim (it’s angular velocity) in the total energy equation. So each rim absorbs the same amount of energy and the amount converted into heat is characterized by the resin and composite structure properties. This is why we ran the test as we did, and it’s why we displayed wheel speed in real time.

    2. You will find that most of the rims offer similar braking power, as we mentioned in the article. In Phase 2 of the Alto test, however, there is MORE energy into the rim and MORE friction, but it still does not catastrophically fail.

    3. Braking power is not directly proportional to brake track texturing. The Bontrager rim had the best braking power in the test and arguably the smoothest brake track. Only 3 rims in the test have a textured track.

    4. This was a blind study. For anyone who believes that we designed our test so that we would “win,” I would like to ask them how this is possible. We had ONE rim from each brand, supplied by Spark Wheel Works, and we had one shot to test them and film them. We had no knowledge of how they would perform, because none of them have ever published actual results. So we went into it with the test protocol and no other information, with a promise to Spark Wheel Works that we would be publishing the study regardless of whether we ended up 1st or 6th (Ryan Mason can confirm this for anyone who asks). It didn’t matter for us, it was about figuring out how these brands compared with each other.

    5. This test was NOT designed to be “real world.” This is in the disclaimer. It was literally a destruction test that had one purpose: give an apples to apples comparison of composite structures and resins. That’s it! Our internal testing includes interval modes, cooling periods, and variable lever force, but it’s a completely different protocol. With the published test we simply wanted to have a more accurate comparison of rims, which is what we accomplished.

    6. Having a higher temperature in this test is not a good thing. All it means is that the conductive properties of the resin are poor and unable to dissipate the energy properly. It also means that the resin will cycle to its glass temperature more often and break down faster over time, like any other thermoset plastic in cyclical loading.

    7. As far as I know, we are the only brand to ever offer actual proof of our carbon clincher heat transfer quality in a controlled test monitored by an independent third party.. It’s very simple to talk about how much better your product is by X%, but I have yet to see proof of any of it. That is what drove us to do this test: to see who was putting in the work and who wasn’t. Simply saying “our product is excellent, trust us” isn’t an answer that any engineer should be happy with.

    8. I can’t think of one retailer in the US that doesn’t have a stack of delaminated rims from various brands, and the stories that go along with them. It is absolutely still an issue, and not one that should be forgotten about.

    9. Many of the brands in this article make the assumption that, because our rims have such good heat transfer properties, that we have ignored everything else: impact, torsion, spoke hole yield strength, etc. We are UCI certified in impact and we internally test to 90 Joules, and have a lab in Sarasota full of equipment used to ensure that our rims are at the forefront of performance and safety standards. Simply because we have eliminated one issue doesn’t mean we’ve forgotten about other tests, we simply wanted to publish one at a time…

    I hope that this test will encourage other brands to come forward and produce results of their testing, and I hope for increased transparency with less marketing. Hopefully they will include Alto in the tests, and we can compare data from multiple sources! The more information for the consumers, the more able they are to make educated purchasing decisions for their particular riding needs!

    • This test was NOT designed to be “real world.” and yet you seem to be using it for self-promotion. If I’d ever tried to pass off as meaningful the results of such a poorly designed test, the high-ups would have taken my lab keys away.

      This “dialogue” you think you’re created reads more like pot stirring to promote one’s brand.

      • Why do you believe it was poorly designed? We controlled every variable in order to test resin properties. That was our only goal, and I think we achieved it. It was done blind and with independent third party participation. I don’t think we could have done anything else to be more clear. Hopefully in the future we will be able to conduct similar tests in order to make it more “real world” for our discerning customers!

        • He thinks its poorly designed for all the reasons that were pointed out in the article. You guys screwed up. Why don’t you just admit it and move on.

        • Your test indirectly rewarded the brake track with the lowest coefficient of friction (your own). Even if input power to the wheel was constant, the fact that your rim ran at a higher speed means that more power was dissipated through the tires, tubes, and bearings before it made it to your rim and the higher speed gave your rim the advantage of (ceteris paribus) shedding more heat via convection. If you want to do this test properly the *LEVER FORCE* should be altered so that the motor runs at the same speed and same wattage for all of the wheels. That way the *BRAKE FORCE*, which is the energy dumped into the rim, is the same for all of the wheels.

          FYI, you keep bringing up that the “grip force” of the average human is 100lbs. The problem with that argument is that you don’t use all of your fingers in applying the brakes: the middle and index finger together only supply about half of that force. Further, if you’re on the hoods of a road bike, your hands are hardly in an optimal position to apply full force. If you’re descending on a TT bike you’d be lucky to apply 15% (by my estimation) of your maximum potential grip force to the lever. Now throw some water into the mix and cut your coefficient of friction in half (or more).

          There’s a reason why Mavic, Enve, Zipp, and others have gone to great lengths and great expense to texture their brake tracks and develop proprietary pads.

          • Facts:

            1) One thing this test shows is simply you can’t melt alto rim regardless of brake pads brand designed for carbon compounds.

            2) Test is biased towards Alto design to work with any pad. 2000 grit sand paper should have been used to just simply show how long it takes to get to peak temp of resin and show how alto rim fails, Gracefully or Specialized way if you do get to melt it with 2000 grit or just sand it down to weakness (which would indicate top notch resin heat resistance and layup)

            4) Wet test should have been shown. (but impossible since you blew up all the rims)

            Can you guys just show how your rim breaks when you poor water on brake track and pads, does it spin at 19mh or basically doesn’t even create any friction?

            3) Can we just discuss what the hell is SPECIALIZED ??!?! thing blew up like a notebook.

        • After 30+ years in the industry I’ve racked up bad experiences with their product and their people to write a scathing exposé on what an abhorrent company Mavic is to deal with on every level. I’m willing to bet the person that cleans their bathrooms can’t even do their jobs right.

    • Thanks that was interesting. Another test from another 3rd party would be nice, but this seems possible. Remember that a lot if people bought competitor wheels for a lot of money and will not accept your results even with unarguable proof though

    • So in point one you claim that only power matters. But in point two, all of a sudden power becomes higher by increasing friction, even if you keep the motor power at 1200 W?
      Also, speed has a significant influence: better heat dissipation by convection.
      I also wonder, was the actual motor power/torque output measured during the test?

    • Regarding point 1: The max dissipation is indeed 1200W, with an ideal (magical) motor. Unfortunately, none exists. Take the two extreme situations: A brake clamped so hard that the motor doesn’t rotate dissipates no watts at the rim. A rim with no brake applied doesn’t just spin up to relativistic speeds – losses in the motor keeps this rim from accelerating to infinity radians per second.

      A realistic calculation of power is force times velocity.

      Frictional force can be tested by testing the deflection of the braking setup, taking advantage of Newton’s second law, every action must have an equal and opposite reaction. The deflection force measured to the brakes is equal to the force felt by the rim from friction. This is not the normal force that was listed in the original experiment.

      To find the velocity, measure the rotational rate of the wheel and the radius from the center of the wheel to the braking surface.

      I do get that this was a destructive test determined to find out worst case rim performance under heat, but I’d guess that the power dissipated was not equal for each rim, which hurts the power comparison.

  3. Campy withheld their rims from the test because the lab wouldn’t use their pads. They were the smart ones.

    The fatal flaw of this test – that the higher friction brake tracks would blow sooner – is so obvious that it’s surprising the lab didn’t think of it.

    • The coefficient of friction has nothing to do with when the rims with “blow.” The higher the friction, the slower the rim’s angular velocity. The less friction at the rim, the higher the velocity — either way, the same 1200 watts of power must be dissipated by the rim.

      The conductive properties of the resin determine how that energy is absorbed by the rim and what temperatures it will reach (and when), and the glass temperature determines whether or not that composite will be able to sustain its structural integrity at those temperatures.

      Hopefully we will be able to run this test again in the future with brand specific pads so that we can compare the data. That will definitely give a clear picture of hose they’ll perform in real world situations!

        • Please watch Phase 2, where the Alto rim ran slower (19.3mph) and therefore had more friction at the brake track. It still ran for 20min and dissipated the heat properly. There is no advantage other than the resin conductivity properties.

          Also note that coefficient of friction at the brake track is not visually obvious. The Bontrager rim, which is as smooth as glass, had the most braking power in this test.

  4. Thank you to Boyd, ENVE and Mavic for giving detailed, qualified testing and information. I also wish to thank Bike Rumor for giving space to set the record straight. Glad you see the importance of experienced, reasoned expert testimony to what is a critical issue of our business.

    We at FSE have reached out to 3rd party industry engineering experts as well as our factory engineers for comment. They have found the “test” lacking and slanted towards a particular conclusion. They reached similar conclusions in agreement with the responses stated here by Boyd, ENVE and Mavic.

    I would like to clear up a false comment Alto made about our wheels: They state that FSE does not treat the brake surface. We indeed do. Reading reviews will tell you this treatment is a highlight of our product and very effective. It very obvious to the naked eye and by the touch. We get a steady stream of thank you comments from our riders.

    Our testing is among the most rigorous in the business. Our resin is tested above 240ºC. We use the latest technology as well as proprietary machines with very unique brake track testing methods under load. We literally test every single rim.

    • Thank you for the input, Dan! I apologize for assuming that your brake track was not treated or textured. It was just based on a visual inspection and apparently I was wrong.

      Please feel free to purchase an Alto rim to test at your factory so that you can publish the results. We hope that more brands will do less talking about their resin glass temperatures and performance, and do more to prove to their customers that it is factual. That was our goal here, so show people how rims actually perform and fail under heavy loading. It was done blind and with an independent third party, so I hope that it is clear how impossible it would be for us to design a test specifically for an Alto rim. Especially when we had no idea how your rim or any of the others would perform. We only had one shot to test and film!

        • Where do we submit them? Haha. If Tour magazine wants one free rim from each major manufacturer then we are 100% on board. We had to purchase these rims (albeit through Spark), and Trek has now purchased one of our rims for a similar study. I think that’s the best way to do it. I’m not sure what Trek plans to do with the wheel or if it will be published, but I have the utmost respect for them and think it’s a great step in the right direction.

  5. Smart of Campy to withhold their wheels from the test (lab wouldn’t use their brake pads). ENVE’s point is pretty obvious: rims with higher friction brake tracks will blow sooner because of the higher friction, but that is a desirable trait in rims. Odd the lab didn’t consider that.

    • When a rim “blows” does not have anything to do with the coefficient of friction. With the system’s energy balanced, heat production and dissipation comes down to the conductive properties of the resin. A good example of this is in the Phase 2 Alto test where there is more energy and more friction in the system, but the rim still does not fail.

      • That’s disingenuous. It totally does depend on the coefficient of friction, because a wheel with a higher coefficient of friction would stop faster and wouldn’t need braking anymore.

        The design problem is applying 1200 W of constant power without considering the deceleration, which is actually the desired outcome of braking. The representative test would be “I’m applying a braking force to a wheel to bring it to a stop (or reasonable speed for say cornering) – how much energy needs dissipating and how does it affect the wheel integrity”. The way you’re doing it is favouring wheel/pad combinations that don’t brake as well.

  6. A lot time is spent designing a good experiment in order to provide the required accuracy and precision and to hold all the necessary variables constant. By using the same pads for each wheel, that’s not done. Pads and CF rims are a system and are designed to work together.

    This test was an experiment designed and performed badly.

    • The “system” that you speak of is simply a choice of pad material that provides a low enough coefficient of friction to keep the rim from reaching its resin glass temperature. For a true high temp resin, any carbon pad should be sufficient and should not cause damage.

      Also keep in mind that we were not interested in testing how these wheels would perform with their pads. We simply wanted a comparison of resin properties and composite quality, which is why we had to use the same pad. If a cheap rim from ebay tests for 9 minutes with a cork brake pad (because they force you to use it as a “system”), and an Enve tests for 7 minutes with an Enve brake pad, we wouldn’t learn anything from that test. Is the ebay rim a better composite quality than the Enve? I doubt it. But hopefully we can run this protocol again in the future, with brand specific pads, to compare the data with what we currently have!

  7. None of the responses is great.
    The test should have been done on a fixed speed motor with brake force modulated to load the motor to pre-set amp set point depending on motor (P equal to VxA). That would ensure every rim received the same brake thermal input. Brake force could be plotted to show which rims is more effective at braking (somewhat). To be done properly though it requires a a brake force modulator tied to a control loop target motor amps. And after all that it would only test heat tolerance, not single use brake effectiveness (which is a different test).

  8. Anyone who is interested in engineering and bikes, follow Chris’s blog, Rockets to Sprockets (linked in the further reading section by Boyd). Great nerdy bike stuff.

  9. Hmm… Enve insists ‘it’s the pads’ while Mavic repeatedly remarks their wheels are safe? My lady doth protest too much. Roll up your pant legs, it’s too late to save your shoes…

  10. Uh, the Boyd test that he did is different cause it’s at 15 km/h. The Alto test was at like 32 km/h and 1200 watts. It’s a different test. It’s also hard to hear Enve and Mavic saying that other brands can’t make a better rim just because they haven’t been around as long. Great products come from young companies in every industry.

    • Most brake track testing is done at that slower speeds. The ISO test is set at 12.5kph.

      We and a lot of others use 15.

      The other test that was referenced where the wheel spins up to a high speed and then the brakes are applied very hard to stop the wheel over and over again is done at much higher speeds than 15 kph.

      • It seems like you just rely on whatever your manufacturer wants you to do, instead of what is best. That video is from the Step factory, right? I don’t think any frame or rim brand tests in house to ISO, CEN, or UCI standards and calls it “good enough.” Almost everyone has a higher standard, and it’s nice to see a test where rims are pushed to the limit in a direct comparison. Even if it isn’t “real world,” at least we can now see how they rank in terms of durability.

  11. Everyone – our comments and site are experiencing some caching issues that, for some geographic areas, are requiring us to clear our cache before new posts and comments will appear. Until we get it fixed, we’ll be clearing it periodically throughout the day and appreciate your patience until we get it fixed. All comments are getting approved or checked as normal,they just may take a few extra hours to show up. Sorry for any inconvenience, we’re working hard to fix it.

  12. Gosh, I wish there were some way to eliminate rim and brake friction. Im trying to think of something. . . Maybe in the future brakes won’t rely on friction on the rim??

    • I agree! What if some sort of weird contraption had a metal disc that two pads where applied on stop it? It would be even weirder if that contraption where aside from the rim heating up and failing a better over all system to stop a bicycle!

      This test was a complete and total waste of time. What a joke.

  13. holy case study batman! Replicates or it didn’t happen (would be my first and biggest criticism)- I mean, that is just a basic tenant of experimental design. Really, it doesn’t matter how well designed the experiment is if it doesn’t replicate it doesn’t mean anything. Next, raw data? the raw data (tracked temp, speed, motor wattage, etc) doesn’t seem to be readily available (though maybe I just didn’t look close on your site or that of the other company involved). The experiment also wasn’t “blinded” (that has specific meaning)- the wheels were not masked in anyway, the experimenter knew which wheels were being tested at any given time and I see no indication that the individual interrupting the data was not aware of which wheel the data was generated from. i’ll restrain from commenting in the specific experimental design as I’m not a physicist, and I don’t have to time to think about it quite enough to decide if I think it reflects anything relevant or not.

    • You’re correct, maybe I shouldn’t have used the word “blind” because it can have two meanings. What I meant was: we had no idea how any of our competitors would do in this test when we began filming. To be honest, we might as well have been blindfolded while collecting data, haha.

  14. Man, you guys can really blab all day about this corny rim test.
    Who exactly is this info targeted to? Pro racers? Doubt it. A bunch of Freds with a masterpiece up their a**? More likely.
    Get a life, dudes.

  15. A few years ago there was a factory in Taiwan that believed they had the solution for the clincher rim failures due to overheating while braking. They developed a surface that worked very well in a particular test. Unfortunately they ignored the basic principle of friction braking which boils down to conversion of kinetic energy into heat. There is no way around this.

    Their rim generated very little heat, and very little stopping power. They were so slippery that they could not pass the EN braking performance test.

    Any friction braking test that you see that does not show a sharp spike in heat indicates that there is insufficient friction generated and thus very little braking is occurring.

    Regarding “better heat dissipation” statement by Alto that is incorrect and impossible. Epoxy resins are all within an error margin of their heat capacity. Per unit weight the heat conductivity is dominated by carbon fiber in the composite product and the heat loss is via direct radiation and convection. Thus regardless of the resin used, it is impossible that a particular carbon rim (Alto rim in this instance) would shed heat faster than any other rim of similar mass, shape and density. The cooling times reported in the Alto test are impossible to achieve in this universe. The additional problem is that the correct way to report heat dissipation is in delta T, not absolute T (change in temperature, not time to reach an arbitrary temperature – the hotter the rim the more energy it has to dissipate)

    The results do in fact fail the basic laws of thermodynamics, but the article is a great advertorial, unfortunately it will generate confusion among the consumers as they may be lead to believe that Alto rims are significantly better performing than other carbon rims. This is a disservice to both consumers and the industry.

    Lastly, Alto rims are made in the same factory in China as at least one other rim in this test. The resin and manufacturing technology are not an industry secret as alluded to by Alto but available to anyone that this factory supplies.

    • I agree 100%. This is how to get your name out there with the least amount of marketing capital. The published results of this “test” will deliver on it’s intended purpose, “it will generate confusion among the consumers as they may be lead to believe that Alto rims are significantly better performing than other carbon rims.”

    • “Any friction braking test that you see that does not show a sharp spike in heat indicates that there is insufficient friction generated and thus very little braking is occurring.

      Regarding “better heat dissipation” statement by Alto that is incorrect and impossible. Epoxy resins are all within an error margin of their heat capacity. Per unit weight the heat conductivity is dominated by carbon fiber in the composite product and the heat loss is via direct radiation and convection…. The additional problem is that the correct way to report heat dissipation is in delta T, not absolute T”

      Bingo.

    • You cannot “fail the laws of thermodynamics.” They are laws, not suggestions. Each rim must dissipate 1200W, and the matrix composition plays a huge factor in how well it can operate as a heat sink.

      Your assumption that all resins are equal is very misguided. A lot of R&D money in the last 10 years has gone into resin technology, and I think it’s safe to say that carbon clinchers are significantly better than they were in 2005. If every thermoset resin was identical then it would be quite simple to make a fool proof carbon clincher without having to think much about it! I wish that was the case, actually, haha.

      Regarding cooling rates, you can’t show them as delta T because it’s an exponential decay. Each cooling rate would have to be displayed as an equation, not a number. We didn’t do this, we simply show the cooling data down to 120 F and allow you to do the integral if you wish.

      As are as being “made in China,” these blanket statements are interesting. We’ve been very open regarding the fact that we cut our hubs and rim molds in Florida, and work with Topkey (Taichung) to lay up our rims.

      • I thought I said that your results fail the laws of thermodynamics. The implication is that they should not have been reported but investigated for experimental error, or for a discovery of a hitherto unknown phenomenon.

        I never stated that all resins are equal. I said that all resins have heat capacity within an error margin of each other. That is what determines their ability to store and thus dissipate heat.

        You have to show delta T, there is no way around it. Rate of change assuming a linear function (which heat loss by convection or radiation in a single phase material is) also takes care of the room temperature issue. There is no need for complex integration that you mentioned.

        Topkey’s major manufacturing lines are in Xiamen, China. They are indeed a very good supplier of various composite parts to the bicycle industry, aerospace too.

  16. Alto’s test rig is pretty mickey-mouse. The competitor’s testing capabilities, as evidenced by the Boyd and Enve setups, are a lot more sophisticated.

    Maybe the Alto rims are a great product, but the test setup doesn’t inspire confidence. (A cynical person could surmise that it is indicative of the level of engineering put into the development of the rims.)

    In my opinion, a good engineer would not have publicly released test results on competitor’s products from such a shoddy test rig.

    It would be nice to see neutral 3rd party tests of rims.

    • Yes, the Topkey factory (where our rims are produced) has a nice jig, haha. We probably could have done the test there. However, we build all of our own testing equipment in Sarasota in order to corroborate results and test to a higher standard. This rig is pretty basic, but we had to build out the motor and program the software from scratch, so aesthetics weren’t really a big goal for us. Plus, none of us are very good at welding!

      • That post right there has about 5 points to where it completely invalidates your testing.

        Ignore the nice factory jig.
        Build a motor and program it from scratch (guessing it’s your first time building a motor)
        No welding skills to build the jig
        First time running the jig (so no baseline is established)
        Think that this makes a higher standard than what is already out there

      • Hi Bobby,
        It’s not about the looks of the test rig. It’s about the functionality.
        Why didn’t you build a computer-controlled actuator to apply variable force the brake pads to produce constant power dissipation? That is an obvious necessity in order to normalize the tests.
        Have you provided detailed information about your motor setup? I don’t remember seeing it.

  17. Always awesome to see a product fail!
    Even better when you can see it blowing in detail and not risking the user during a ride!
    For me this is a “let’s blow some rims thing!”.
    I think alto lost it when they stopped pushing the rim until destruction!
    Alto please go further!

  18. OK so in my opinion the motor system is a huge problem in accuracy. To get rid of all the variable i would get a huge flywheel then spin upto a certain RPM – this is an accurate amount of energy to dissapate. Then see how long/well/fast the wheel can be braked repetitively. This eliminates all this discussion of how you pull the pads or how long for.

    The proper CEN setups use a big roller mass for this reason. if you completely de-couple the motor entirely you can analyse the actual real world task which is dissapating a certain amount of energy. The bigger the hill the larger amount of energy, but its always finite.

  19. I like to see tests that destroy products!
    For me its a shame Alto stopped the test at 9lbs!
    Alto lost the test when they were the only brand/product that failed when they didn´t fail under the test circunstances!
    Alto please give us an Alto rim destroyed! If it takes too long increase time lapse speed to more than 5x we have time!!!

    • I agree, we really wanted to see it blow up as well! Our rim did fail at the end of the Phase 2, which is why we stopped the test. We just didn’t know that it had failed until inspection!

      But that rim is still built up and we’ll put it back on the jig soon to see if we can blow it up! The issue is that, with 11lbs on the lever, the wheel will barely turn and the tire may start to slip on the drum. So we may have to add some weight to the top or change some things if we’re going to be successful in running it to failure. We’ll see! Either way, we’ll be recording it and posting the video.

  20. I’m trying to remember when any of these brands rims have failed from prolonged braking heat? As in during the Tour, Giro, or Vuelta when ridden by hundreds of pros down the worlds steepest mountain passes under real world racing conditions.

    • Not the same thing. This was a test of carbon CLINCHERS. The pros ride carbon TUBULARS. Nevertheless, your argument is somewhat valid for the thousands of enthusiasts and amateurs using clinchers. Not applicable to pros though.

  21. “Best to be thought a fool and remain silent than to speak up and remove all doubt.” -Abe Lincoln

    Kinda feel Alto should just zipp it.

    Funny, we always bitch about the big companies cost/marketing lines but it’s these small companies that are the ones to watch out for here. And really, lets face facts Alto is a couple of kids fresh out of college with minimal experience. Oh sorry, one of then was minion at cannodale’s parent company once (which doesn’t make wheels) and is a “pro racer” on the road in the US. Eh. Remember what Bob Roll said about being a pro in the US? Yeah it applies here.

    Know people who work and carbon at nasa. They laughed at the Alto guy’s comments. As manu of us lesser engineers did.

    • I apologize to you, Mr Pink! I wish I could have lived up to your expectations of being a faster pro racer, better frame designer, better engineer, and older. One day you will be proud of me!

      On a more serious note, we actually worked with the NASA engineers here in Florida on a composite rim prototype a couple of years ago, and know many of them. What a small world!

  22. Finally, if you’re starting a wheel company, and find that your wheels are testing 10x better than every leading wheel manufacturers’, with generally good reputations for producing high performance wheels that are also safe, maybe you should ask yourself, “what’s the matter with my test.”

    • And another piece of good advice…
      If you publish other rims being destroyed, you better be sure your test methodology and data acquisition is completely, 100% sound otherwise you risk what we are seeing here.

      Should Alto have just tested only their rims, shown the test method and results, the conversation would be much different.

      • We had talked about this – only publishing our rim test. However, since no other brand has ever published their test and results in their entirety, it wouldn’t have any context. We were also VERY curious to see if the claims of reputable brands would actually hold up. We were curious, and we figured others would be as well!

        I’d also like to point out that an established company saying “our rims are good because we’ve been around for a long time” should not be good enough for you. And claiming that engineers are incapable of creating a superior product simply because the company isn’t 100 years old is offensive. As engineers, we want proof of these claims or it simply means nothing to us.

        • It’s crazy that alto is getting pounded for this. It’s clear as day.

          Alto rims – designed around user to not melt with common brake pads. user centric thinking here.

          The “established” “old” “smart” “companies” rims – are result of profit driven manufacturing cost reduction to the maximum, and then sell $80 brake pads, that actually made by another company which make their particular cheap manufacturing cost design rim not melt. Profit centric thinking here.

        • I think the context in comparison to other wheels isn’t really needed unless you are in fact saying they are dangerous. If you published only Alto rim data and gave context about normal brake power loads in real world situations compared to the test, that alone would show your wheels are good for use

  23. As a Materials Engineer, Polymer Scientist, Cyclist and friend of Alto supported Athletes I can’t fathom why Alto thought it would be a good idea to publish this ill-conceived experiment. If Bob believes they have truly created a miracle heat dissipating rim with equivalent braking performance he might want to hire an outside product development consultant to assess their findings and experimental design before providing further comments and any additional test results.

    I fear this marketing stunt is going to backfire..

    • Hi Fred! This is precisely why we had the test corroborated by Spark Wheel Works. We also were sure to display our results in their entirety, and followed the scientific method to a T. This was literally the opposite of a marketing stunt, it was a rim study based in curiosity due to the fact that none of this data has been published for 20 years!

      • To be fair.. I do believe that this test and the results will stimulate further discussion on test methods and design/perfromance criteria. That’s a good thing! It would be great to see a well designed third party test. Paging Kraig Willet.

  24. If resins that are more heat resistant result in other tradeoffs for wheels as Boyd says then disc brake rims should be better as there is no need for high heat resistance, just whatever temp the trunk of a car can get to.

  25. Quick question for Bobby. Apologies if you have already explained this, but there has been a lot of info flying about and I find myself pondering why your rim cools so quickly in Phase 1, but in Phase 2 it is actually slower to go from its max temp down to 120f than many other rims, even those that reached a higher max temp. In other words, the 10x faster cooling only seems to occur in Phase 1, which seems odd. Is it because Phase 2 was run consecutively, so more of the rim structure was heat soaked by that time, and so there was less potential for conduction? How would you establish if that is indeed the case, and that you simply didn’t get a bad reading on Phase 1?

    • Good question, man! There is definitely a lot of information flying around, haha. But that’s a good thing!

      The important thing to note about the cooling curves is that they are an exponential decay. That means you can’t just subtract two number and call it a cooling rate, because the rim cools more quickly early on than it does when it gets closer to room temp. That is what you are seeing in our phase 1 test: we were already super close to 120 F, so it got there extremely quickly during the early part of the curve. Phase 2 is a more accurate representation of the cooling in an Alto rim, but it was definitely slower than we would have hoped for. We think the resin may have built up some residual strain from phase 1, but that’s just a theory.

      The cooling rate of each rim would be accurately expressed as an equation for exponential decay, not as a number. We didn’t go that far in this study because it got to be a bit too technical for what we thought people would be interested in, so we simply displayed the numbers and allowed people to take that next step if they wished!

      I hope that helps!

      • Thanks for the reply! I get what you are saying in regard to cooling rate not being linear. Putting aside the topic of alterations to the resin from previous heat cycles, I am a little confused about which conditions cause faster cooling. My understanding is that the greater the delta between the rim and surrounding air, in other words, the greater the difference in temp between the two, then the faster the rim will cool. As the two (rim and air) get closer to equilibrium, the rate of heat loss from the rim will slow.

        In Phase 1 and 2 though, it appears that the opposite is the case. Again, putting aside changes to the resin from Phase 1 heating, I would tend to assume that the speed at which the temp drops from 263.3F (the Phase 1 peak temp) to 120F would be very similar in both Phase 1 and Phase 2. If that is the case, then it means that in Phase 2, it took a whole 330sec for the rim to go from its peak of 287.6F down to 263.3F, and then only an additional 34sec to drop the rest of the way to 120F. In other words, it seems that the greater the difference in temps between rim and air, the slower the rim sheds heat.

        What am I missing here?

        It would be interesting to see thermal images of the whole rim during tests of this nature to see what the temp of rest of the rim structure looks like when compared to the braking tracks themselves.

        • Ah, I think I see what you’re saying. But remember that in phase 1, the temperature began to drop after pad glassing. So the time that was measured to 120 F at the end of the test was from 263.3 to 120, it was from 135 (or whatever the exact temp was that it ended at) to 120. Those results are a bit odd because the Alto rim ran long enough to cool itself during the actually test, so the delta T was significantly less. Similarly in phase 2, the rim was at about 182 F at the end of the test, which is when the clock starts on the measurement down to 120. Does that help answer your question?

          Yes, we hadn’t thought about a thermal camera and I regret not doing that. We’ll have to do it for our rim in a future test. Hopefully we can get more rims from other brands as well so that we can have a comparison! I just don’t think tests mean quite as much without having reference points!

          • Ok, I think I get you now! You are saying that the rims peak temps were reached well before you ended each braking Phase, and so they had already shed a substantial amount of heat by the time you started to stopwatch to measure cooling to 120F. I probably would have gotten that from paying close attention to the video, but I was simply looking at the tabular info in the green table above, and had assumed that the cooling times listed in the far right column were measured from a start point of the temp in the middle column.

            Regardless of the technical aspects at play here, I want to thank you for your endurance with the questions. A lot of other companies would have either just dropped a single PR style reply to everyone and left it at that, or would have gotten hot and bothered (no pun intended) by all the antagonistic questions.

            • Replying to myself, I just wanted to add that if what I wrote above is correct then that means that the “10x faster cooling” that everyone is getting all worked up about, saying it is physically impossible with current resin systems, etc… isn’t quite what it appears. My assumption is that most people are getting this “10x” figure from the same green table that led me astray. From what Bobby wrote above, the Alto rim was already down to something like 135F by the time the Phase 1 measurement began, so it only had to shed 15F in that 34sec period, not 100+F like most of the other rims presumably did.

              The fact that the Altos started to cool in the latter part of each Phase due to pad glazing/glassing, seems to suggest that, in a sense, a rim that can survive past this threshold when the pads degrade is somewhat on easy street from there on out, as it has already hit peak heat and made it through.

              I had been operating based on the idea that Alto may have substantially improved conductivity in the larger rim structure to improve heat shedding, but what I wrote above seems to open up a more traditional possibility, which is that their resin and filament wound brake tracks have created a rim which has sufficient heat tolerance to survive past the pad glazing/glassing point. The braking surface itself will play a role in when that transition point occurs for the pads, so that is a variable of which it would be good to get some more measures. Personally, I’d prefer a rim/pad combo where they pads are cooked before the rim, which Alto seems to have achieved. On the other hand, I would prefer to achieve that by upping the rim’s abilities, rather than creating an environment with a braking surface that lowers the pad’s abilities. Unless I am missing some other indicator (which is totally possible), then without more comparative testing, we can’t really tell what mix of these things is at play here.

              • You’re spot on, and people have made this mistake regarding the cooling times. The cooling times are from the END of each test down to 120 F, not from max temp down to 120 F. For nearly every rim, the end of each test and the max temp are the same, because that’s where they failed. It just isn’t the case in the Alto tests.

                By no means did we change the coefficient of friction of our rim to help it handle heat better, that would be totally insane, haha. It is the same surface finish as our 2017 rims, albeit slightly different from the new winding process. We simply improved the resin specs and conductivity properties to allow the rim to act more efficiently as a heat sink, and drive the temperature at the brake track down.

                I’m always happy to help and to answer questions! We try to not only have a top tier product in the industry, but to have the best customer service to go along with it. You can contact me any time through the contact page on our website, and it will come straight to me.

  26. Huge props to the industry as a whole for not letting this fly, to Chris Uberti for providing stellar context (I look forward to reading more of your articles), and to someone in particular for reaching monumental levels of irony when they called my comment on BR’s previous post “self-aggrandizing.”

  27. “It is unfathomable that a wheel company, that has only existed for less than five years, could suddenly have a wheel that performs so dramatically better than the others in the test.” – Enve

    I’m sure when Refrigerators came out, Ice companies said the same thing.

    According to your logic than I can conclude that Campagnolo rims then must be just something out this world compared to yours, since campy existed for 72 years before you founded?

    Whats unfathomable is $900 for rim that costs $500 from competitors, and costs probably a legit fraction to made after you covered the tooling and I don’t even get Campy logo on it for $900 a pop!?!?!??!

    Carbon is cheap, abundant and causes cancer and you charge $900 for a rim. Disgraceful like rest of bike industry.

  28. Study of tribology (lubrication and friction) is extremely complicating. Proper experiment for such objective requires years of experience and even if you had an absolute genius, would still cost a lot of money to obtain proper results. This is a “garage” test so you can say you did “something”. Should not be published like this in a press environment, because one person taking this article as a “conclusion” is one person too many that was mis-lead. That is a risk to the industry.

    These types of test information do not get out because of the cost and experience involved. They’re super proprietary information, intellectual property. Any brand would be stupid to publish any detail of their own tests! It’s kept secret so that these fab-less “designer” brands cannot try to gain cheaply without proper experiments. They all test every possible rims out in the market, plus tons of proto-types, every day, by numbers of engineers, improving their test setup on daily basis.
    Sorry, but sample of n=1 test should never be seriously considered for any proper results. Why do you think it costs so much money to properly test? Needs to statistically satisfy the results, or no publication. Amateur of the bikerumor to publish such article.

    If you are not buying into ENVE/Mavic/Zipp and such brands’ tests, then a proper 3rd party test organization must be established, not the UCI “sticker” lab, but morelike in the automobile crash testing.
    But you would not want that because that would wipe out all fab-less “designer” wheel brands. You would be required to send hundreds of rims for every model and versions you “design” and would not be able to afford it. That is not fair to the big brands? Well it takes that many wheels to obtain a proper experiment data.
    Everybody is free to experiment however way they want and publish in their own pages and say whatever they want. But to publish in a press? Nothing in this article and wheel test are truly useful information.
    However, comments made by these brands are actually super useful and actually has a lot of hints to what they do with testing. This is where every fab-less “designer” wheel brands should be paying attention, too! So Bikerumor and Alto were able to suck this info out of the big brands, this is your big achievement with this test and a big break!

  29. Congratulations To Alto for creating the longest ever wheel discussion on bike rumor! Being 200 lbs and love descending mountains in Malibu makes me want the best failure free wheels when clamping down on the levers descending Tuna Canyon.

  30. wow my head is spinning, ….here is the short of it Alto rims can take more heat, but they have less friction to stop or offer less stopping power, hence if a rim offers more friction it heats up more , but it also stops faster…I guess brakes should stop faster, so I take the ones that have more friction because ultimately stopping faster is what brakes should do and understand that I think I can probably stop before the rim blows up. …right

  31. To me the biggest inconsistency in the results is the Phase 1/2 results for the Alto rim. How does it take 34 seconds to cool from a max run temperature of 263.3 F, but suddenly takes 364 seconds from 287.6 F in phase 2. The additional 24.3 F resulted in an order of magnitude increase in cooling time. It makes me suspicious that the first number is a typo (e.g., 340 seconds) otherwise the material would have to be undergoing a phase change to have such a substantial change in radiative properties.

    • Sorry for the confusion here! You aren’t the first person to read the results this way, and it’s our fault for not presenting them more clearly. The cooling time to 120 F is from the END of each test, not from the max temp. For every test but the Alto rim, the max test was the end of the test because that’s when the rim failed. However, the Alto rim experienced pad glassing after such a sustained time at high temps, so the temperature began to drop. For Phase 1 it only had to go from 135 F to 120 F at the end of the test, which is why it was so fast.

      Also note that a simple delta calculation doesn’t work as a “rate” for these cooling curves because they aren’t linear. They are exponential decays, so each curve would have to be shown as an equation in order to portray cooling rate accurately.

      Sorry again for the confusion, I hope that helps!

  32. I personally have seen Boyd carbon rims delaminate in the Santa Monica mountains. Luckily, not catastrophic but the rims were toast. I’ve seen it with Zipp and other brands. So, I don’t put any faith in the validity of their tests because in the real world, they can and do fail.
    They very well know their rims fail because they warranty replace them.

    I would like to know how many warranty claims they have had for destroyed or heat damaged rims?

    This Alto test opens a very important discussion that the big manufacturers were unwilling to discuss.
    Kudos to Alto simply for that.

  33. If lots of effort is done to get a good brake track for rim brakes shouldn’t carbon disc wheels be cheaper and stronger? No special effort is needed for design of the brake track (cost) and with no heat buildup on the rim don’t have to use higher temp resistant resins so don’t have to deal with those tradeoffs (strength)

What do you think?