Derby Rims Ups Options & Inventory, Adds 40mm Wide 26″ Carbon Rims

Derby Rims lightweight wide carbon fiber mountain bike rims

We first spotted Derby Rims at Interbike last year, where the brand was just seeing the light of day as founder Ray Scruggs carried a couple samples around the show floor.

Following our post, he got flooded with orders and had up to a 2-1/2 month back order. Fortunately, his factory has expanded, so now he’s got inventory and even expanded his offerings to include a 40mm wide 26″ model. He’s also added different layup options, offering the original lightweight XC layup, plus new Heavy Duty and DH layups for heavier or more abusive riders. Depending on which size wheel, you can pick from two of the three…

Derby Rims lightweight wide carbon fiber mountain bike rims with no bead hook

He’s offering a 35mm wide 29er rim and 40mm wide 27.5″ rim in Light, Heavy Duty and DH layups. The new 26″ rim will come in HD and DH layups. The outer width and inner profiles stay the same, all of the additional carbon layers are added inside the hollow section. That means the hookless bead and 10mm deep center channel all stay the same, as well as the bead channel, all of which Scruggs says lets them set up as tubeless rather easily.

Going from Light to Heavy Duty adds about 20-25g per rim, and HD to DH about 30-40g per rim. That puts them at the following claimed weights:

29″ – XC 460g / HD 480g / DH 515g
27.5″ – XC 440g / HD 460g / DH 485g
26″ – HD 440g / DH 465g

No, those aren’t the lightest rims out there, but that’s not the point. Scruggs’ goal was to create something super wide and stiff first, then durable, and then at a reasonable weight. He says more than 1,000 rims are out on the trails with great results and feedback. But, he says you can run a narrower tire (that’s lighter weight) and get the same traction as a much heavier wide tire on a standard width rim and come out with a lower total system weight. We’re hoping for our own test set later this year to see how that works out IRL.

In other news, the sufficient stock means he’s now able to offer industry and wholesale pricing for shops and their employees. Contact him from his website, below, for details.

DerbyRims.com

Comments

craigsj - 08/21/14 - 8:49am

“But, he says you can run a narrower tire (that’s lighter weight) and get the same traction as a much heavier wide tire on a standard width rim and come out with a lower total system weight.”

Why do people believe that, and why would anyone do that? We don’t have that many choices of tires anyway.

I have a set of Derby rims and am pleased with them, but this comment is just stupid. They can make a tire work better but they can’t turn one tire into another.

J - 08/21/14 - 9:42am

Why do we have another hookless rim when we don’t have a hookless tire? I was excited about this until the hookless part.

ayyggss - 08/21/14 - 10:27am

craigsj

it changes the profile of a tire essentially make it a “different tire ”

ideally a 2.5 tire should be on a high 20 is mm rim . and the tire should be 2.5 in in width .

now if you took a 2.35 tire and mounted it on the same rim the profile would be 2.35 . take that same tire and mount it on a rim that’s 40mm wide and it will spread the bead essentially making the foot print almost as wide as the 2.5 tire but using less rubber to do so . this extra width also reduces pinch flats by pushing the bead so fat apart that the tire will fold inside the rim as apposed INTO the rim (snakebite) which allows the use of a lighter tube ( if your not tubeless ). the main benefit of running wide tubeless wheels allows the bead to be spread further apart making burping a tire much more difficult to do.

the only downside of width is weight and user error for using a rim to wide .you can essentially stretch a tire so fat making it useless . ie. a 2.0-2.10 on a 40mm rim

craigsj - 08/21/14 - 11:47am

“now if you took a 2.35 tire and mounted it on the same rim the profile would be 2.35 . take that same tire and mount it on a rim that’s 40mm wide and it will spread the bead essentially making the foot print almost as wide as the 2.5 tire but using less rubber to do so”

No it won’t. It will make the carcass wider but won’t change the footprint at all. These tires have knobs on them and those knobs don’t relocate themselves with rim width.

“the main benefit of running wide tubeless wheels allows the bead to be spread further apart making burping a tire much more difficult to do.”

Also not true. The main benefit, of you ask fans of wider rims, is improved handling.

“the only downside of width is weight and user error for using a rim to wide .you can essentially stretch a tire so fat making it useless . ie. a 2.0-2.10 on a 40mm rim”

Again, not true. 2.0-2.1 tires will work fine on a 40mm rim. maybe not optimal but better than on a narrow rim.

It’s this kind of uninformed thinking that leads to the Derby claims in the first place.

groghunter - 08/21/14 - 12:16pm

sad that basic geometry is hard for people. you’re saying the tread pattern doesn’t become wider. Absolutely not true. the tread width, simplified to 2d geometry, is a curved line. If you measure the absolute distance between the endpoints of that line, on a standard width tire, you’ll get something close to the claimed width(BS tire width markings notwithstanding.)

take the same line, and reduce the degree of curvature: you’ve just done the same thing as putting a tire on a wider rim. If you now measure the absolute distance between the endpoints of the line again, THEY ARE FARTHER APART. also, because you’ve reduced the curvature of the tire, you increased contact patch size, because more of the tire touches the ground before the angle of curvature lifts it away. Which is the same effect as lengthening the 2d line.

groghunter - 08/21/14 - 12:20pm

Hit submit too soon: lengthening the 2d line is what you’re doing when you switch a 2.35 tire to a 2.5 tire.

Spreading the endpoints of the line farther apart ends with the same absolute width as using a longer line, in these circumstances.

ayyggss - 08/21/14 - 1:25pm

^^^^^^^^ there’s the technical explanation .

besides you completely contradict your self

Again, not true. 2.0-2.1 tires will work fine on a 40mm rim. maybe not optimal but better than on a narrow rim.

wider is better . tubeless is better bottom line

JBikes - 08/21/14 - 1:26pm

Most of the advantage of wider rims has to do with increasing effective sidewall stiffness for the same pressure and increasing air volume, allowing for low pressure while maintaining the same flat resistance. There is a point of diminishing return though – at some point the wider wheel decreases volume, and physcially the tire wont be able to remain its bead.

Pinch flats are likely reduce because the marginal gains of stiffer sidewall and increased volume act similar to increase pressure (on a narrower rim). Greatly eliminating “snakebite”. Case in point, a 2.35 tire is a good 20mm wider than a 40mm rim and will easily snakebite at low enough pressures. Wider rims just make it much lower than most will go or for the normal impact forces seen.

Auto tires manufactures have long given recommended rim widths for their tires. Wider wheels typically result in a higher performing tire envelope for the same reason. I can easily see bike tire OEM starting to optimize tires for rim widths, if they aren’t already doing so. case in point, a wider rim may improve contact pattern, but is the 2.35 tire was design for use on a 24mm rim, this wont be the case.

groghunter - 08/21/14 - 1:35pm

It isn’t the sidewall stiffness that decreases burping: It’s keeping higher angles of force from levering the bead out of the rim. RC dropping diagrams: http://www.pinkbike.com/u/richardcunningham/blog/Tech-Tuesday–Wider-Rims-Are-Better-and-Why-Tubeless-Tires-Burp-.html

craigsj - 08/21/14 - 2:26pm

“you’re saying the tread pattern doesn’t become wider. Absolutely not true. the tread width, simplified to 2d geometry, is a curved line.”
The tread pattern doesn’t become wider. The tread is molded onto the carcass and would have to spread out to become wider.

Sure, the tire profile is curved. It also flattens under load. This changes nothing.

A wider rim increases the circumference of the carcass. The tread on that carcass is the same.

“also, because you’ve reduced the curvature of the tire, you increased contact patch size”

No you haven’t. The contact patch size is governed by the load and the tire pressure. carcass width only affects the shape.

“sad that basic geometry is hard for people.”

Well, grog, on that we agree.

Why don’t you try an experiment where you use the same tire on two different width rims. Using the exact same load and tire pressure, take an imprint of the tire contact patch. You’d be astonished to learn that everything you’ve said is wrong.

craigsj - 08/21/14 - 2:37pm

There is no advantage to increasing the air volume inside a tire. There is already too much. It is true that there’s value in extra width AND extra height, and collectively this is referred to as extra volume even though the air captured by that volume isn’t helpful.

Bicycle tires would perform better with a dramatic DECREASE in internal air volume. That’s the idea behind double tube systems, one of which was reported on this site recently. With those systems you can have a progression in spring rate that you want but that oversized air volumes can’t provide.

Sidewalls are straighter with a wider rim so they work better. All the rest of the “explanations” here aren’t. Air volume isn’t it, contact patch isn’t it, wider tread isn’t it. The tire’s maximum width is increased, but that occurs at a point that never contacts the ground.

JBikes - 08/21/14 - 3:03pm

@groghunter,
With repsect to sidewall stiffness – tires roll and deform due to lateral loads. Your correct on the cause of tire burping, but wider wheels for a given tire will reduce lateral deflection, resulting in better contact patch management and better response from the tire. This is well understood in both the automotive and motorcycle world. That doesn’t mean its without tradeoff though, and it is not as simple in a dynamic tire load like a bicycle experiences (as opposed to a car)

@craigsj – I largely agree with your last post, but I am not convinced larger air volumes are worse than small ones. It really depends on what your riding as well as your suspension tune and rider weight. Low speed technical riding may benefit from larger air volumes as the tire can deform more. Lower air volumes will increase internal pressure more for a given amount of tire deflection and this may not alway be desireable as it will prevent more rubber from hitting the ground (i.e. low spring rate). Higher speed riding may benefit from lower air volume for reasons you allude to.

Motivated - 08/21/14 - 3:03pm

I love my derby rims – 29er “XC”. I run 20psi with Nobby Nics and get better traction and comfort, without the tire folding over, than running 24psi on my Arches. I believe the explanation that wider rims support the sidewall better. I have had zero problems with the beadless design and quality Schwalbe tires. I’ll buy derby rims again – an XC light (400g) option would be nice.

HillDancer - 08/21/14 - 3:19pm

I’ve run conventional aramid fiber folding bead tires on the Derby 650b rim, both tubed and tubeless. At low tire pressures high volume tires use, if a tire is not designed “hookless” as J would like to see, it’s a non-issue on Derby’s hookless rim. I would prefer less elastic beads such as carbon, agreed.

Another non-issue is mounting relatively narrow tires on Derby rims. I used 38mm nominal width tires on the 40mm rim with all positive results.

For a given nominal width tire, air pressure & load, increasing rim width alters the shape of the tire’s contact patch, not contact patch area. The contact patch shape becomes less elongated on a wider rim, which reduces pneumatic trail, resulting in reduced slip angle. A desirable effect for performance handling.

JBikes - 08/21/14 - 3:25pm

HillDancer is much more eloquent than I. All my rumblings were basically distilled in his/her concise last paragraph.

groghunter - 08/21/14 - 3:47pm

@HillDancer: As you mention, that’s all true for a given air pressure, but the increased volume allows you to run a lower air pressure, & in fact almost requires it, in practical use, due to reduced tire deflection at a given air pressure & increase in volume.

Thus why fatbike tires are usually running 6-10 PSI, & thus why in practice, a larger volume increases contact patch.

@craigsj: If I’m so wrong, & wider rims don’t improve performance, why does every other sport with spinning wheels use rims that are much closer to tire width than MTB? even road bikes. Heck, even Fat bikes, at least compared with MTB.

Shabs - 08/21/14 - 4:05pm

I can confirm what craigsj posted about the the need for decreased volume at higher speed DH applications. If you think of a tire as an air spring, you make it more linear by increasing volume, which makes bottoming the rim easier for a given pressure. In the two months that I’ve owned wide rims, I’ve killed four tires from tubeless casing snakebites, running pressures in the mid 30′s. As they stand, I don’t see the point of high volume DH rims. For them to be useful to DH riders, they will need the DT Swiss Procore system.

PR - 08/21/14 - 11:43pm

Wouldn’t spreading a tire too wide cause the cornering knobs to be useless?
I don’t want to corner on a bare sidewall.

Automobiles don’t really have that issue I guess; sort of a weird analogy for a mountain bike tire, imho.

Note: I lean when I turn, though I believe some XC riders do not.

Leonard - 08/22/14 - 4:13am

I have a 50mm rabbit hole rim with 2.2 Rocket Ron. I am not sure about the science but it looks cooler on the 50mm rim than on the crank brothers rim.

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