Tech Speak: Brake Fluid Break Down & Implications for Road Disc

As one of the first things you should learn as a mechanic when it comes to disc brake maintenance, brake fluid basics are important to know – especially before working on different brake systems. On the surface it all seems pretty simple, you pick the right fluid for your brake, and bleed as necessary. However, there is more to brake fluid than just DOT or Mineral oil.

When it came to the lastest installment of our Tech Speak features, we though it might be a good idea to revisit the life blood of your hydraulic braking system. To gather as much technical information as possible, we went straight to the source and invited Formula, Hayes, Hope Tech, Magura, Shimano, TRP, and SRAM provide their response to our questions. While it may be a refresher course for some, the varying unedited responses we received from some of the biggest brake manufacturers in the industry makes for a good read especially on fluid implications towards road discs, and how your fluid choice can impact your ride (for better or for worse).

UPDATED: SRAM’s official responses have been added to the mix, after the break! Update #2: additional answers from Nick to some questions in the comment section.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

What does your company use for brake fluid, and why?

Formula (Engineer): We have always used premium DOT4 fluid. Now we are using DOT4 SHELL DONAX ULTRA for all our Formula brakes. DOT4 has a higher boiling point than mineral oil and increases vapor lock resistance by being less hygroscopic than DOT5.1 and others

Hayes (Tim Abhold, Director of Engineering): We use glycol based brake fluid, commonly called “DOT Fluid”. Our systems are compatible with DOT 3, DOT 4, and DOT 5.1 fluids, but the systems are factory bled with DOT 4 fluid, which we also sell in service.

Hope Tech (Woody Hole, Progress Manager): We are currently use DOT 5.1 brake fluid in all of our brakes. This is the brake fluid with the highest dry boiling point (260°C).

Magura (Stefan Pahl, Engineer and Project Manager): Magura uses mineral oil for bicycle brakes since introduction of the very first hydraulic rim brakes in 1987. Mineral oil does not absorb water, is easier to use and does not damage paint or skin. The lower boiling point of mineral oil compared to DOT fluid is compensated over time, as DOT absorbs water, even through seals and bladders, leading to a lower boiling point, see also here. That’s why DOT has to be changed regularly. Mineral oil can stay forever in the brake without regular changes.

Shimano (Nick Murdick, Lead Multi Service Technician) : We use mineral oil for several reasons. The main discussion you usually hear between DOT fluid and mineral oil is that DOT fluid absorbs moisture and mineral oil doesn’t, it’s hydrolytically stable. As DOT fluid absorbs moisture from the air, the boiling point drops. Mineral oil doesn’t absorb moisture from the air so the boiling point never drops. Another thing you hear is that DOT fluid is regulated by the federal government so the quality and characteristics are guaranteed. Obviously this is important, which is why Shimano tests every single batch of our brake fluid to confirm that the viscosity and boiling point are perfect. We actually see this as a major advantage of using mineral oil. We don’t have to trust anyone else’s testing standards for the fluid they make.  Since every Shimano brake uses Shimano brake fluid, we have complete control over the process and can assure consistent performance. Let’s take a look at those DOT standards though; they have specific targets for fluid that is both dry and wet (defined as having absorbed 3.7% water by volume):

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Chart provided by Shimano

As you can see, our boiling point starts higher than any DOT fluid and never drops.

We also use mineral oil because it won’t harm the finish on the bicycle or your skin. Along those lines, it was important to us to use a fluid with minimal environmental impact if a line is ruptured during a ride.

SRAM/Avid:  We use Glycol based fluids, specifically DOT 4 and DOT 5.1 for a number of reasons.  DOT fluid has a high boiling point, is manufactured to an agreed upon set of safety standards and is readily available in any auto or motorcycle store.  Also, any DOT fluid residue remaining on a brake after service is comparatively easy to clean up with water instead of some potentially harmful solvent.

An important point about the hygroscopic nature of DOT Fluid is that by absorbing the water into the fluid it is preventing pockets of water from forming that remain separate from the fluid in the system.  Water is heavier and settles to the lowest point in the system, such as the caliper.  This means that while the boiling point of the mineral oil remains high, the boiling point of the system is now that of water, only 100C/212F.

Both mineral oil and DOT Fluid are hazardous to your health and the environment.  Both fluids must be handled with appropriate protective equipment and disposed of properly.

TRP/Tektro: We also reached out to TRP, and haven’t received a response.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Can consumers use fluids other than your specific branded fluid in their brakes?

Formula: ONLY AND ALWAYS DOT4 brake fluid! Different brand can be used of course. Shell is recommended.

Hayes: We recommend only Hayes branded fluid, because all our validation and laboratory testing is performed with our Hayes fluid. Other fluid brands may perform acceptably, but without test data to verify the performance we cannot endorse their use.

Hope: Our customers can use other brake fluids with all our products, however, we generally recommend only DOT4 or DOT5.1 as alternatives. Both fluids are widely used in the car and motorcycle industry so are easily available at most good cycle and car shops. DOT3 can also be used if none of the above are available.

Magura: No, no other fluids can be used, even mineral oils, as they may damage the seals due to different chemical properties, letting the seals shrink or expand.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Shimano: Absolutely not, mineral oil is an unfortunate term to use because it is so vague and generic. The term mineral oil can describe a lot of different compounds. It’s kind of like the term salt, which refers to much more than just table salt. Most of us are probably aware that the mineral oil that you buy at the drug store is not the same as the mineral oil we use in brakes, but that extends to different brands of mineral oil brake fluid as well. We should really call it “proprietary brake fluid” but I guess that doesn’t have the same ring to it. I can tell you with absolute certainty that Magura fluid will destroy Shimano brakes in a very short amount of time. I’ve seen it happen several times. The rubber seals in the system have to be specifically designed to interact with a specific brake fluid. If you use a different fluid, the seals will interact differently. Specifically, when you put Magura fluid in Shimano brake, the lever feels spongy and the pad contact point changes because the square edge seal at the caliper is breaking free from the piston at a different time.

There are third party companies that make mineral oil brake fluid and it says right on the bottle that it is compatible with all mineral brakes. Shimano has never approved a third party brake fluid to be compatible with our brakes and we never will. How is it possible that one fluid can work in both Magura and Shimano brakes if Magura fluid destroys Shimano brakes?

SRAM: We recommend only DOT 4 and DOT 5.1 fluids, but DOT 3 can also be used without affecting the seals or anything else in the system.

Have you ever performed testing with, or produced prototypes using other fluids?

Formula: Weekly and in every weather condition. But up till now Shell is the best tested brake fluid.

Hayes: Hayes serves a wide variety of brake markets from bicycles to snowmobiles, motorcycles, heavy equipment, and military applications. We have performed testing on a large number of brake fluids, hydraulic fluids, and synthetic fluids.

Hope: We have carried out extensive with different fluids since making our first hydraulic brakes back in the early ‘90’s. Some of those tests have focused on mineral oil, however, in our experience DOT5.1 is consistently the best performing fluid to use in our brakes.

Magura: Of course we tested different mineral oils, but never DOT fluid, as that would require a new design of seals and seal seats. We keep with mineral oil.

Shimano: One of the advantages of engineering your own fluid is that you can make something that specifically fits the needs of a bicycle. So yes, absolutely, lots of different fluids were tested while developing Shimano Mineral Oil. Viscosity, boiling point, and hydrolytic stability were key factors in engineering our fluid.

SRAM: We have tested a number of different fluids, including silicone based and mineral oil based products.  To date, nothing has met the performance benchmarks of our currently product.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Will the potentially higher heat buildup with road discs have any effect on fluid choice?

Formula: Sure, but not only for road disc. Heat dissipation is one of the main targets in the brake industry. You have to consider that when you brake, the torque you apply on the wheel will be transformed into heat. In addition, the job of the fluid is not the heat dissipation, but only to resist the high temperature generated during the braking action. Heat dissipation is one of the greatest areas of testing you have to perform during the design of a new brake. With higher brake performance you will have higher temperatures that need to be dissipated.

Hayes: Definitely. In fact, the heat generated in road discs should also drive investigations into performance optimized mechanical systems, to avoid the fluid boil failure mode entirely.

Hope: We have always used the brake fluid with the highest dry boiling point in our V-Twin CX/Road disc brake unit. Also heat management due to the size of road discs is more important regardless of the type of brake fluid used.

Magura: The potentially higher heat build up on road disc brakes has to be compensated on the “mechanical” side, i.e. bigger rotors, bigger surfaces for heat dissipation. The same as on road to dirt moto bikes (road bikes generally use huge double rotors and big calipers, dirt use single rotor and smaller calipers).

Shimano: I don’t really think so, because you have to think about all of the things that happen as a brake starts to overheat. It’s not just boiling fluid. The first thing that changes with pad temperature is the coefficient of friction – this is an important thing to understand. As a brake pad heats up from room temperature, the coefficient of friction goes up as well and the brakes start to work better. If your pads are designed right, the sweet spot for their coefficient of friction will match up with the normal operating temperatures of the brake. At some point though, as the temperature continues to rise, the coefficient of friction will drop off suddenly. The lever still feels good and isn’t coming to the bar, it just feels like the pad has no grip on the rotor. This is what we call “fade.” It’s a little confusing because most people use the term fade to talk about the lever pulling to the bar but that’s not exactly right.

As the brake continues to heat up, glazing can happen. This refers to the brake pad material breaking down and liquefying. This can be one of the causes of fade. When the pads cool down, the material will recrystallize on the surface of the rotors and pads, greatly reducing the coefficient of friction until the glaze is worn away. Of course, if the coefficient of friction is reduced by glazing, the brakes won’t work as good. If the brakes don’t work as good, you use them more. If you use them more, they are more likely to overheat. If they overheat, they can glaze again.  It’s a vicious cycle.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Finally we can start talking about fluid turning to gas. We know that a hydraulic system works because the fluid is relatively incompressible and the pressure you put into the lever comes out at the caliper with almost no energy lost. Gasses are compressible, so if there is a lot of air in the system, or if the fluid turns to gas, the pressure you put into the lever does nothing more than compress the bubbles and the caliper pistons don’t move. To take that concept a little further, when an air bubble is squeezed, it gets smaller and the pressure goes up. If the pressure in the bubble reaches the pressure in the surrounding system the brake will work again. That’s why pumping the lever makes the brakes come back a bit.

It is possible for the fluid to boil before the pads fade or glaze if the boiling point has dropped far enough, but generally the pads start to fail before the fluid. There may be a system out there that is better for road, or there may be some road-optimized solution in the future. The important thing to realize is that you have to think about how the entire system works, not just the fluid.

I think you’re asking these questions because it’s starting to become clear that there might be some problems with just taking a hydraulic disc brake and putting it on a road bike. Even though a road bike is lighter and the terrain is smoother, heat is more of a problem on road bikes than on mountain bikes because of the way you use the brakes. Long downhills with lots of brake dragging build up a lot of heat. Also, because it is easier to stop a lighter road bike people want to use a smaller rotor, which dissipates less heat and makes things even worse. If this leads to fluid heating up and boiling, the brakes stop working. I think this is why you’re asking about different kinds of fluids and how we can change the fluid to handle the higher temperature. But the fluid is only a single piece of the puzzle. If the fluid had a higher boiling point the brakes would just fail because of fade and glazing instead, and it would happen at about the same temperature. You really have to think about the whole system, and when you do the answer becomes clear. Heat management is the solution. We shouldn’t be thinking about how to make the brake handle more heat, we should be thinking about how to keep heat out of the dangerous places, direct it to safe places, and then get rid of as much of it as possible.

People are already starting to think about this a little, they are choosing bigger rotors that can dissipate more heat. Without a complete system that can manage heat, this is about the only option. That’s a compromise though. You should be choosing your rotor size based on the power needs of the bike, not the heat dissipation needs.

SRAM: The choice of fluid is only part of the heat management equation.  Proper design of the pads, rotors, pistons, and caliper as a system as well as extensive validation testing is necessary for this new application.  Any fluid can be used in a braking system as long as the system is designed for it.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

As far as the internals of the brake go, is there any difference in the size of the parts between DOT Fluid and mineral oil that would make it easier to fit in a road lever?

Formula: No, referring to dimensions but absolutely yes when referring to the material of the seals. The rubber compound that we use in our brakes is not compatible with mineral oil (and vice versa). If you bleed a brake that is designed for DOT4 with mineral oil, you will destroy all of the seals in few hours (and vice versa).

Hayes: No. The differences in fluid performance are slight in relation to the system in general and do not drive sizing decisions. Fluid will, however, drive internal components material selection to ensure compatibility.

Hope: No, there is no difference in terms of the size of the parts but there is a difference in the rubber materials used. Using one type of fluid instead of another would cause the seals to swell and eventually brake failure.

Magura: No, there is no difference in size.

Shimano: There are some small differences; our brakes are designed around our brake fluid, so the size of the oil ports is related to the viscosity of the fluid. The balance of those things controls how oil flows around the system, which affects bleeding, lever feel, and the ability to keep air in the reservoir where it is safe. The main differences are in the seals. DOT fluid eats seals so they have to use a specific kind of seal in their system. Even then, seals need to be replaced every few years. If you look around the bike industry, every company that makes DOT brakes offers rebuild kits and every company that makes a mineral oil brake does not.

SRAM: Seal material is critical.  Porting size is also a consideration as viscosity changes due to temperature can be greater with oils than with DOT fluid.  In our experience piston sizes must also be considered as mineral oil has shown higher compressibility.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Speaking of temperatures, over the years there have been various reports of extreme heat or cold affecting brake performance – is that a fluid, or an engineering thing?

Formula: Good question. To give you a short, simple and clear explanation you have to consider two brake fluid variables: 1-viscosity & 2-dry boiling point. These two variables are connected. The target is to have higher boiling point and lower viscosity (lower viscosity means a fluid like water at ambient temperature, higher viscosity means a fluid like honey). With lower viscosity the lever movement and the feeling of the brake is maximized.

Unfortunately (generally) a brake fluid with a higher boiling point has a very high viscosity at low temperature. In the same way a brake fluid with a lower viscosity has a lower boiling point at low temperature. We chose a brake fluid that combines these two characteristics in the best combination to give the customer a great performing brake in all conditions.

Hayes: Different fluids definitely perform differently as temperature changes. Compressibility and viscosity changes with temperature are a key characteristic of the fluid.

Tech Speak: Brake Fluid Break Down, and Implications for Road Disc

Hope: Brake performance issues shouldn’t occur with a well maintained brake system – whatever the weather conditions. In circumstances where the weather does affect performance, brakes using mineral oil brake fluids are more adversely affected by the cold as opposed brakes using DOT fluid. Over extended periods of use, because DOT fluid is hygroscopic, the boiling point will drop and affect brake performance. This is why it is important to replace the brake fluid every year or two depending on the usage.

Magura: Compensating for extreme heat is a matter of dimensioning. The bigger the surface and the mass equal weight of a brake is, the better it can handle heat (assemble a moto brake on a bike and you´ll be fine. It´s just the weight…) Compensating for cold is much more difficult, because it depends on the chemical properties of the fluid. Generally all fluids get thicker, more viscous, at lower temperatures. This leads to a slower response of the brake, the thicker fluid has to be pressed through the same small ports inside the brake. As an extreme just take water: it will freeze and the brake will not work!

Shimano: All bicycle disc brakes will stop working if they get below a certain temperature, but it’s not because of the fluid. If you want proof just take a bottle of brake fluid and put it in the freezer. The failure point is actually with the square edge seal used in bicycle brake calipers. These are designed to pull the pad away from the rotor when you let go of the lever so they don’t rub. The seals need to flex a very specific amount as the piston moves out and then help bring it back in. This seal is also responsible for the system auto-correcting for worn pads. The seal flexes out as the piston moves to a very specific point, after that it breaks free, and the piston slides past the seal. If the seal gets too cold, it loses its flexibility and the piston breaks free too soon. When this happens, the first pull of the lever goes all the way to the bar and then after a few more pulls there is almost zero free stroke in the lever and the pads rub on the rotor because they haven’t retracted. The quick fix is to ride around in circles with the brakes applied to heat up the seals, then just push the pistons back in and try again.

Brakes get much hotter from friction than anything the weather will throw out at them so the only thing I can think off in regards to a hot day is fluid expansion. If a brake sits in very hot direct sunlight the fluid can expand a bit and either lock up the brake or let fluid out of the weeping port. The weeping port is there to handle expanding fluid but it can be a little concerning to see fluid coming out of the lever. If the brake has locked up it’s just because the weeping port works best when the lever is being pulled to move fluid around. When this happens to a Shimano brake with Servo-Wave and Free Stroke Adjustment you can just turn out the free stroke screw to open the master cylinder transfer port up a little and allow fluid to flow up into the reservoir again.

SRAM: The system as a whole is designed and tested for optimum performance in a given temperature range.  Extreme heat or cold can affect this performance, but generally the system can be designed to work well in any extreme one would be willing to ride in.  We perform extensive validation testing to verify these limits.

Are there any fluids other than DOT or mineral oil that could be used for hydraulic brakes on the horizon?

Formula: Nothing on the horizon.

Hayes: There are a variety of fluids currently in use in other industries that could be applied to bicycles. Fluid selection is always a function of finding the right balance of performance, stability, cost, and environmental impact for the market/consumer.

Hope: Not that we are aware of at the current time.

Magura: At the moment these are the fluids of choice as they have to be good on high and low temperatures, lube the system, be incompressible, be low on costs,….

Shimano: I think that any new specially designed brake fluid would still be called mineral oil. We’ve already come up with a specially designed bicycle brake fluid ourselves and we haven’t found anything better yet.

SRAM: There are many fluids available for a variety of industrial hydraulic applications which could be used in a brake system.  With that in mind, DOT Fluid was specifically designed for brakes and has been in use for years in the automotive and cycle industries.

Takeaway:

While there are basically only two categories of brake fluid in use for bicycle disc brakes, due to engineering and manufacturing differences, no two systems are alike. While that drug store mineral oil, or generic DOT fluid may save you a few bucks short term, manufacturers spend a lot of time and effort engineering the brakes as a system and using the wrong fluid could cost you dearly in the long run.

To me, one of the most interesting bits of info happens to be the quoted boiling point of Shimano’s mineral oil. I’ve always heard the argument that mineral oil has a lower boiling point than DOT fluid (reinforced above from Formula, Hope, and Magura), yet there is it. To my knowledge this is the first time I’ve seen the boiling point of Shimano’s mineral oil in print – which if true (their huge resources make it quite possible), makes a pretty strong case for Shimano’s mineral oil – higher boiling point, hydrolytically stable, and safe for your skin, bike parts, and the environment.

Overall, as we suspected, brake fluid should have little overall effect on road disc brake performance. As Nick mentioned, heat management especially for road, is more about mechanical systems than one fluid or the other.

Update #2: There were two excellent questions in the comment section regarding Shimano Free Stroke and Mineral Oil specifically, so I reached out to Nick to see if we could get the answers. Nick is actually in Japan currently continuing to learn about the new product, but he took the time to shoot back some responses below.

Matt: If you buy a bottle of Shimano mineral oil, how long does it remain good for: A. if unopened? B. if opened and then re-sealed (i.e. some poured out for a bleed, lid then replaced)? 

Shimano: Mineral oil is fine to keep on the shelf pretty much indefinitely.  That’s actually why we are able to sell liter sized bottles instead of just little one time use sized ones.  It doesn’t make much of a difference if the bottle has been opened.  The same goes for inside the brake, we recommend replacing our fluid as it gets dirty.  This is about once a year for the most serious riders who mainly stick to the same bike and ride off road.  If the fluid stays clean, like if the bike is in storage, it doesn’t need to be replaced ever.

Justin: I would love to hear Nick Murdick explain what exactly the Free Stroke adjustment does?

Shimano: Free stroke is defined as stroke of the lever before the pads start touching the rotor.  The free stroke screw simply changes the starting point of the master cylinder piston.  If the screw is all the way in, the master cylinder piston will be all the way in, and the free stroke will be the shortest.  Turn the screw out a bit and the master cylinder will start further out.  Because it has to travel further before it closes off the reservoir port, the free stroke is longer.  In the picture of the clear brake posted above, the free stroke screw is turned all the way in.

I’ll admit that it is confusing because it seems to have the opposite effect when you turn the screw.  The stock position is all the way in and that’s where most people like them.  If you do nothing but turn the screw out, the pad contact point moves out.  So it feels like you’ve made the free stroke shorter.  The problem is that turning the free stroke screw also effects your initial reach adjustment.  The pad contact point came out, but the starting position came out more.  So it’s always at least a three-step process.  First set the reach adjustment so that the lever starts where you want it, then adjust the free stroke screw to get the amount of free stroke you want, then turn the reach adjust knob to put the lever back where you wanted it.

I would personally like to see a lever that allows for an even shorter free stroke adjustment but as it is, when the free stroke screw is all the way in, the master cylinder is right up against the reservoir port.  So really the only way to give people less free stroke would be to sacrifice clearance between the pad and rotor.

 

Comments

Rob - 04/11/13 - 9:14am

No comment from Avid/Sram? I think this article is very interesting, but it should at least have a note as to why Avid/Sram were not included… maybe they declined? Inquiring minds want to know! (Also, i would think Avid is second to Shimano in terms of sales volume)

Charango - 04/11/13 - 9:25am

Very informative writeup. What fluid does Avid/Sram use?

Jimjam - 04/11/13 - 9:30am

If Shimano mineral oil has such a high boiling point, then why do they create so many ‘things’ to reduce the heat of their brakes. They have giant fins on their calipers and laminated steel and aluminum rotors, that kind of seems contradictory.
If Shimano mineral oil has the reported high boiling point, then there would be no need for the designs, ie fins and laminated rotors.
AND where is Avid?

don - 04/11/13 - 9:45am

Awesome article, the absence of Avid is unfortunate. I hate DOT fluid, okay perhaps a bit strong, but I maintain a fleet of bikes for the family and DOT is less than desire-able for certain. Especiall DOT 5. I had planned to try mineral oil in my avid brakes, an older set to experiment. My assumption, if the claims above are true, is it will trash the seals quickly. Anyone else tried it that can verify? Any reponse is appreciated.

don

gravity - 04/11/13 - 9:46am

Jimjam, there are more reasons to want to cool your rotors than boiling your fluid. Boiling or not, excessive heat will be generated by prolonged braking, and this will lead to diminished braking. Shimano’s IceTech system is, without a doubt, the best cooling system that any brake maker has yet created.

mtbrider - 04/11/13 - 9:48am

Did Shimano pay for this to be written, or did they write it themselves and have it posted?

It’s rather disingenuous to call this ‘Tech Speak’ when it’s really a marketing piece for a particular company.

gino - 04/11/13 - 9:52am

@jimjam – Re: shimano: Not necessarily. Don’t forget what heat can do to the pad and rotor compounds in the form of glazing and fade.

Ploutre - 04/11/13 - 9:53am

SRAM and Avid use DOT5.1 (but it also works fine with DOT4).

Yoshi - 04/11/13 - 9:56am

Shimano is still the best period… I’ve got 7 year old XT’s and only have needed to change pads. They operate like new…

Darryl - 04/11/13 - 10:12am

Shimano have the fins etc because at the moment, they simply have the best performing, most reliable brakes.

Go ask any shop to bleed your brakes, if they are Shimano, they will probably do it while you go have a coffee, that’s if it ever needs bleeding at all, most consistently used shimano brakes just don’t give problems.
The only time I have seen problems are when the bike has been hung up by a wheel over an extended time and a little bit of air in the reservoir has made it’s way out of the top of the reservoir into the system because of the orientation of the bike.
Ceramic pistons don’t corrode and the things just keep going until the square edge seal simply wears out.
Usually you have updated your bike by then.

Every other brand are b*tches to bleed, need flushing regularly or the lever pumps up with moisture and the pads scrape, and then people just let a little fluid out and then the pistons corrode from the moisture, and the seals stuff up as soon as you try and push the pistons back to fit new pads.

Even just reading the responses above, it’s easy to tell who knows their stuff.

I’ve got XX gear on my dually, but my brakes are XTR………and no I don’t have the finned pads, normally they are simply not needed for my singletrack style riding.

don - 04/11/13 - 10:22am

Hard to blame the Shimano guy for knowing his product and spending time on his replies. Good product marketing guys do that.

The real sauce is on the trail and Shimano brakes are really good based on my limited experience and the crew I ride with. I am the only one on Avids, most of them bought bikes with Formula brakes and replaced them with Shimano.

I have only one Shimano set in our fleet, it is the only set that has NEVER required maintenance and works flawless. Actually far better than any of the brakes I own. These are the m575 which is pretty low on the Shimano food chain too. I was going to take them off when we bought the bike and replace with avid to be consistent and now I’m considering changing the rest of our bikes.

don

Zach Overholt - 04/11/13 - 10:25am

All, we did reach out to Avid, but haven’t heard back. It’s not that they have declined, we just haven’t received their responses. Same goes for TRP/Tektro.

Kristi Benedict - 04/11/13 - 10:27am

mtbrider – No one pays for content on Bikerumor. The Shimano guy just gave a thorough reply. We invite as many brands as we can to participate in these types of posts, give everyone a reasonable amount of time to reply, then compile their answers and publish it. We only edit for grammar, not for content. It’s an unedited window into the industry that we think people will enjoy.

gringo - 04/11/13 - 10:33am

As a guy who has ridden and bled every commercially available brake in the past 7-8 years I will say Shimano wins based on (long term) braking performance, user friendly servicability, and non-toxic fluid.

The absence of SRAM here might have to do with the fact that anyone there who knows about the brakes is busy sending replacements to pissed off dealers :-)

Ed - 04/11/13 - 10:43am

That was highly informative. For me there’s no reason to hear from Avid on this. Avid brakes require far more maintenance than any of the others in my experience. I’ve bagged dozens of them for warranty over the years. Shimano’s spokesperson clearly had his stuff together for that interview. And no, I don’t work for Shimano.

Jimjam - 04/11/13 - 10:47am

It is interesting to see people finally talking about brake fade being a characteristic of the pad compound. This is why there are different compounds, some fade less than others. Unfortunately this post is not about pad fade, it’s about fluid and understanding the differences between and why the manufacturers use them. I like DOT fluid because I can be in any town around the world and still have the opportunity to buy it if I need it.

Justin - 04/11/13 - 11:29am

I would love to hear Nick Murdick explain what exactly the Free Stroke adjustment does as I have not gotten a straight answer from any of the reps at Shimano I have spoken to!

Rob - 04/11/13 - 12:12pm

@zach: thanks for the avid update!

Chuck Dick - 04/11/13 - 12:44pm

All I took from this article is that Hope has an employee named Woody Hole.

Dale - 04/11/13 - 1:06pm

I’ve had the same thing on my XC bikes – Avid Elixr cr discs fail & bleed nightmare. Ended up buying Magura Marta sls and no problems at all.

I still hate the idea of road disc brakes, so ugly.

cmetz - 04/11/13 - 1:09pm

baffling that anyone would even consider a brake besides shimano after reading this. their superior design and engineering aside, it’s obvious from Nick Murdick’s answers that Shimano knows hydraulic brakes, and obvious from everyone else’s that they don’t know them as well.

Matt - 04/11/13 - 1:10pm

I expect other folks would like similar answers for other fluids, but for me…

If you buy a bottle of Shimano mineral oil, how long does it remain good for:
a. if unopened?
b. if opened and then re-sealed (i.e. some poured out for a bleed, lid then replaced)?

Thanks.

jonas - 04/11/13 - 1:27pm

That is one of the best pieces of bike literature I’ve ever read, and I love how the shimano tech had the actual boiling points there to back up his statement rather than just making vague claims like the formula guy. The shimano tech should be commended for knowing his product and taking the opportunity to show why it’s so good.

That being said, I’ve had my magura louise brakes since 2008 and I’ve been completely happy with them. I live in Vancouver and ride the north shore, squamish, whistler, pemberton, etc. It’s steep, wet, punishing, awesome terrain and I’ve never felt a lack of stopping power. My magura gear has never failed me, I’ve never experienced fade or any other loss of performance and they hardly ever make any noise. I change the pads as needed, about once a year. After sitting for a couple of months one winter the front brake needed bleeding, which took about ten minutes and returned it to full performance.

When the elixirs came out they looked super sexy and I thought I might get a set, but having heard about all the bleeding issues I’m glad I didn’t.

At a guess, I think the reason that magura in north america isn’t more popular is that they haven’t set up much in the way of sponsorships or oem relationships with bike companies.

bin judgin - 04/11/13 - 1:49pm

I’ve warrantied a few of the 2011-2013 shimano brakes, and the avid brakes from 2012 on are actually getting more reliable. They are not without issue, obviously though. The 09-11 elixirs were some of the most unreliable stuff made, though.

Mindless - 04/11/13 - 1:50pm

Avid brakes are the worst. Shimano and Formula FTW. And, yep, Shimano are easier to take care about.

Bought a liter of their brake fluid, sits mostly unused – only needed to bleed when assembling new lever/caliper. It just keeps working. Formula requires yearly bleed – but I have to admit it performs nicely for its weight.

Jimjam - 04/11/13 - 3:51pm

@jonas, did you click on the link to Shell Donax Ultra? It’s pretty impressive.
Dry boiling point of 554°F and wet boiling point of 383°F!

I would be interested to see the test Shimano performed to come to the conclusion they did.
I’m always skeptical when a manufacturer does their own test and doesn’t release how it’s conducted.

@Bikerumor you should test the manufacturer’s brake fluid independently to see how they stand up. If that’s even conceivable for you to do.

Max - 04/11/13 - 5:28pm

Funny, all of them are claiming to have the best :)

Their *blabla* don’t use other brake fluid, Buy our 1.000.000$ per liter is nonsense. I drive Shimano Brake Lever with a Magura Marta SL Caliper. The Fluid is 50% Magura Blood and 50% Shimano oil. Works perfectly, all sealings are ok and the performance is superior to the most other brakes. After crossing the alps this brake is still in a very good condition. My rotors got thin and a light blue color but the rest is ok ;).

Sram mentions the “compressibility of fluids”…. thats marketing nonsense! The Compressibility of fluids is such low, that you will need a system with (nearly) endless stiffness to measure the differences. But all Bicycle Brakes have very weak master cylinder units and calipers plus weak hydraulic hose, so every fluid (even water) is the strongest/stiffest part of the system by far :D

CJ - 04/11/13 - 5:51pm

Having come from the moto world and religious maintenance of hydro systems associated with those vehicles. A few things pop out in this article.
NEVER believe a mfg claims on BP w/o some sort of independant testing. I find the claims Shimano fo 500+ deg to be shocking and that is an understatement. MTB industry isn’t as highly evaluated as the moto world in systems testing at least published testing.

Shimano’s use of MO in lieu of DOT is largely based on the litigious nature of the US and the assumption that these vehicles see infrequent use in many cases and seasonal breaks that would wreak havoc on a system that absorbed microscopic amounts of water over these periods of idle storage. The moto world is well aware of this and is far more inclined to take necessary steps to remediate the issue rather than ride it and forget it and their systems are 3-4 times the capacity as well.
All that said it is a fact in an ideal performance only world DOT 5.1 would be a better choice for the hardcore brake user in the DH/AM (maybe road) world and provide additional headroom for high temps if needed.
The aluminum sandwich rotors and finned pads that Shimano now has avery smart tech and further illuminate how superior Shimano products can be. Every brand should copy this.
Someone kill the idea of Carbon brakes rotors though, these work on high speed heavy use environments like F1 and MotoGP but only after enormous warm up cycles prior to race starts, but not on anything else.

RideMechanic - 04/11/13 - 6:57pm

The boiling point comparison provided by Shimano is a little bit of smoke and mirrors….. Mineral oil only absorbs very small amounts of water so if testing the BPt of the oil, the table holds true. But water or dirt or gunk does still sneak around the piston seals which is why the oil gets dirty. And if this does not absorb into the mineral oil it hangs around as….water. BPt 100oC. And more to the point, oil is less dense than water so water is concentrated at the bottom of the line right near the heat producing pads.

Drew - 04/11/13 - 7:11pm

Congrats guys on presenting such a well balanced article from all parties concerned. Not sure what some of the others who have posted comments are on about saying no Sram/Avid?

Zach Overholt - 04/11/13 - 7:18pm

@Thanks Drew. The post was updated after we heard back from SRAM – we hadn’t heard back when it first went live, but once we did, we updated it.

Drew - 04/11/13 - 8:07pm

@Zach. Yes mate I thought that may have been the case. Great website by the way, I read it everyday.

jenbe - 04/11/13 - 8:13pm

almost 2 years later and the magura oil still hasn’t destroyed my saint brakes… there is a surprise.

Rob - 04/11/13 - 8:43pm

MY Tektro brakes have been running Johnson’s baby oil for almost a year now and they have been fine.

There are numerous threads on MTBR.com about brake fluids.

Tony - 04/11/13 - 9:00pm

Interesting article I have been working on automotive brake systems for over 20 years and know a lot of the time the manufacturer just wants to sell you their brake fluid . As for avid alixir brakes do have some design flaws in their product. The hydraulic system isnt a problem, once you know how to bleed them its easy but they vibrate and chatter(turky gobble noise) especially on hard tails and under hard braking the cone washers can move. They are only small problems that can be easly fixed and the brakes work fine for a long time. I dont understand why they dont do the fixes in the first place.

Matt - 04/11/13 - 9:55pm

Shimano’s table is misleading. The DOT specifications are *minimums*; you can easily get DOT fluids with much higher boiling points (600F+).
Also the % change in BP is complete nonsense, as it is based on a scale with an arbitrary zero point (Fahrenheit). Rinakine or Kelvin may have some merit for % change, but even then it’s a meaningless value when all the wet and dry numbers are different.

Matt - 04/11/13 - 9:56pm

That was supposed to say Rankine…

dangerjonny - 04/11/13 - 10:09pm

mineral oil all the way, eay to work with and doesnt melt the paint of my bike!!

Mindless - 04/11/13 - 10:19pm

Whether Shimano’s table is misleading or not does not matter at all. The proof is in the performance. They are robust and essentially maintenance free. If maintenance is needed, it is stupid easy. With Icetech rotors and pads, they have the least amount of fade – boiling point does not matter, it is the operating temperature that matter. It does not matter that their blend is proprietary – it is easily available, if you ever need it.
DOT 4 in my Formula works fine, but it is much more pain to maintain.

Mindless - 04/11/13 - 10:20pm

P.S. And AVID brakes suck, no matter what they use. Could be unicorn urine, they still suck.

Nic - 04/11/13 - 10:46pm

I think you will find the DOT boiling point figures provided are MINIMUM requirements to meet those DOT specifications. There are a lot of products that exceed those figures and that of Shimano.
I use a high quality race fluid in my brakes such as Motul RBF 660 which outperforms Shimano at 617°F.

Zach Overholt - 04/12/13 - 1:09am

@Matt and Justin, check the bottom of the post for Nick’s responses to your questions!

Andrew - 04/12/13 - 5:25am

It doens’t really matter what the boiling points of the fluids are. the performance and reliability of the whole system is what counts. In my expereince Shimano is the easy winner.

Hani - 04/12/13 - 7:54am

Thanks for a very informative article!

WannaBeSTi - 04/12/13 - 2:56pm

I can see there are a few mechanics on here posting Shimano FTW. Well, in my shop, Sheeemano brakes are the king daddy. We’ve had only a small number of brakes from ‘em to give a headache, but Avid? It’s almost easier to have the brake warrantied for the slightest problem.

Shimano, Hayes, Magura, Hope, Formula-reliable

Avid-reliable to sound like a turkey gobble or grinding gravel, brake pressure to just fall off, 2-4 attempts are needed for a really good bleed

kuan - 04/13/13 - 8:55am

One major drawback with mineral oil. It does not work in cold weather!

LMStuff - 04/14/13 - 12:52am

I ride a 2003 Yeti ASX with Hayes HFX-9 disc brakes and have been beating the crap out that bike for 10+ years now with very little downtime even in the winter as the winters are very mild where I live. I still ride it 2-3 days a week and keep it well maintained minus the brake fluid. I have only needed to change the pads and adjust the levers. Not once have they failed me even the most severe downhill riding for extended periods of time, very cold single digit /teen temp rides, and all day summer Moab rides. I haven’t touched the fluid and they have never leaked a drop as far as can tell. I know time is ticking, as soon as one fails I will most like replace both. This the awesomest bike I have ever owned, it just keep going, no major failures other than the rear hub blowing up a few years ago, both my front and rear shock still hold air and I never had to get them rebuilt. Hopefully Sea Otter will guide me to the right replacement bike this month, I have been saving up some serious $$$$ for one. Looking forward to get some test rides in. Bronson 27.5 Santa Cruz? The new 29 Enduro? 29″ Camber? Stump Jumper? IBIS? another Yeti? I want something that I just can’t break very easy, that takes a severe beating and keeps me safe by not failing at the wrong time and want to get under the 30lb mark! Willing to go carbon rims too. Sure I want a lighter bike with lighter stuff. But I have been reading reviews on a bunch of bikes and the failure rates of some of these newer very lite disc brakes scare me. Same with the rear shocks too. Maybe its just those people posting more since they had a bad experience.

What’s the best, most reliable hydrolic disc brakes out there that will last and very low failure rate, fairly light and low maintenance would be nice too? Based on my limted experience Hayes has not done me any wrong.

stephend9 - 04/14/13 - 12:43pm

Thanks Zach for this very interesting article.

Two follow up questions:
1. I’d like to hear SRAM/Avid respond to Shimano’s claim of having the fluid with the highest boiling point.
2. I’d like to hear Shimano respond to the SRAM/Avid claim that the water pooling at the lowest most heat vulnerable point (caliper) negates the benefit of Shimano fluid not absorbing water.

I think we would all like to see a follow up article further dissecting the intricate braking system such as ones about current pad and rotor technologies.

Nate - 04/14/13 - 10:03pm

“CAN CONSUMERS USE FLUIDS OTHER THAN YOUR SPECIFIC BRANDED FLUID IN THEIR BRAKES?

Magura: No, no other fluids can be used, even mineral oils, as they may damage the seals due to different chemical properties, letting the seals shrink or expand.”

BS!!!! I’ve used a 50/50 water and anti-freeze (sometimes more antifreeze or more water or complete one or the other) in my Maggies and have had bleeds last for YEARS. This mixture takes literally like 50% less effort to pull than maggie blood. Maggie blood while good, isn’t the only thing that can be used in maggies. Infact, it performs WORSE than the anti-freeze/water mixture. Not to mention an entire gallon of Anti-freeze is like half the cost of a liter of maggie blood.

Dominik - 04/17/13 - 6:46am

As for Shimano / Magura – we are successfully using a Delphi LHM+ for almost a decade in our shop – the only people that complaint about the LHM+ over the original fluids usually cannot bleed them properly.

David French - 04/18/13 - 4:53am

My only gripes with Ice Tech is the finned pads can rattle and the rotors are comparibly difficult to straighten. I prefer to buy Hope brakes because they are proudly British made and because in years to come I will still be able to buy spare parts.

matt - 05/22/13 - 3:44pm

Matt,
I like your argument over % change in boiling points for fluid.
Unfortunately we live in the U.S. where few people understand the use of Kelvin.
However one can argue that Celsius is arbitrary as well due to the fact that mineral oil, dot fluid and water don’t freeze and boil at the same points i.e. 0 and 100.

You won’t find MOTUL 660 in most bike shops, many use generic oils available from distributors or worse, oil from the local car shop that are held to minimums of boiling points to save a buck.

http://en.wikipedia.org/wiki/Brake_fluid
I know it’s off the internet but check out the article posted above.
As somebody that has run both systems for years, try them both out for a few months and let me know how it goes :)

ThEGr33k - 06/18/13 - 9:14am

Motorbikes use Dot fluid. I would imagine that the motorbike industry have put more money into R&D into brake systems than the pushbike industry and have clearly come to the conclusion that DOT is the better option. Companies like shimano are relatively new to this tech and seem to have gone the other road to keep customers paying them money for over priced liquids.

Francis - 07/15/13 - 10:50pm

My perceptions are based on 40 years of experience working on two wheeled conveyances both motorised and pedal powered. 20 years working as a cycle mechanic have certainly revealed some noticeable differences in the way companies do their product developement. I have definitely found Shimano Hydraulic brakes to be more reliable, require less bleeding and provide more consistant braking than the other brands. Hope, Formula, Tektro, Hayes and Magura are all reliable for the most part and provide functional braking. Some are easier to work on than others but overall I would consider their manufacturing integrity as equal. I had Hope hydraulic disc brakes on my 1994 Foes Weasel which were outstanding for their era and included a splined rotor attachment system that Shimano has copied.
Avid and Sram which are essentially the same require the most bleeding and usually it takes several attempts to get all the air out of the system. The Sram Corp. consistantly releases product on the market without doing enough testing or developement and appear to rely on the consumer to test their product. In some countries their warranty criteria are absurd and attempts to have poorly engineered and manufactured product replaced or repaired are complicated by proceedures that are clearly aimed at minimising the number of warranties they have to deal with. This is not just limited to brakes. Early Reverb seatposts had a high failure rate and to date Reverb failures have accounted for 98% of all the dropper post warranties my customers have had. The brands owned by the Sram Corp have consistantly released product without properly testing it. For example Rockshox Judy forks (plastic damper cartridge that leaked almost immediatly from new), Plastic Motion control units that seize and start binding, Early gripshift, Truvative isis bottom brackets that rarely lasted more than a few months. They have been lucky and have made some product that is functional but many of their products are cheaply made and overpriced. If you take a Shimano shifter apart it looks like a well engineered and manufactured item. A Sram shifter looks more like a $2 shop toy inside. Sram rear derailleurs are more plastic and less durable. My hardcore MTB customers can wear out Sram rear deailleurs in less than 2 years. An equivalent priced Shimano derailleur will last twice as long. Looking at manufacturing from an ethical perspective it is easy to see the differences between the two companies. Whilst they are both trying to make profit one has a far greater emphasis on engineering integrety and the other appears to be more focused on providing shareholders dividends.

Shimano have placed a lot of emphasis on heat disipation with the use of mixed metal rotors and cooling fins. It appears as though they are trying to minimise the transfer of heat into the hubs. My experience is that disc brake compatable hubs that use cone, locknut and loose ball bearing systems require constant fettluing to keep the cones tight. It appears as thought the heating and cooling of the hub with resultant expansion and contraction causes the lock nuts to back off and the cones coming loose. This allows dirt etc to enter the hub. Cone and ball hubs are essentially road technology that is not appropriate for off road use. If a motorcycle company produced a dirt bike with cone and ball hubs no one would consider it acceptable. As beautifully engineered as the shimano MTB disc hubs are the company needs to sort out this issue and attempts to minimise the amount of heat going into the hubs with elaborate rotors and finned pads is unlikely to solve this.

pepe - 09/13/13 - 1:38am

the best info…thank you so much.

Post a comment:

Comment sections can be a beautiful source of knowledge, conversation and comedy. They can also get pretty ugly, which is why we've updated our Comments Policy. If your comment isn't showing up or suddenly disappears, you might want to check it out.