Derby Rim Test

The last 2 years has seen a push from the MTB industry to grow our rim size by .75" on either side for a net of 27.5" versus the old 26" that has been around for decades. Before 650B (27.5") even saw the light of day some had been pushing Wagon Wheels or 29" bikes as the most capable in terms of roll over, ground covered and speed as a whole. The big wheels to help bikes get over rougher terrain. But they also seemed less playful and just a bit less snappy in the turns. This is where the 650B is supposed to make up for its smaller diameter a more playful feel with a wheel that has shorter spokes. During this time many rim makers have been altering their rim widths to accomodate wider tires and to also effect traction while allowing riders to run lower pressures. While bigger hoops roll somewhat better they also add weight as do the tires. Ray at Derby realized this and once a few Chinese rim makers had begun production of Carbon hoops for most of the market an oppurtunity opened up that allowed the production of wider, bigger rims that stayed around the 500 gram mark.

 

The wider tire profile allows more traction. This is mostly notable under braking on the front wheel not so much the back. Derby also claims the ability to run lower pressures. We are now running around 26-32 psi on them depending on the trail. The cost of the rim makes it hard to get down to low 20's like Derby claims they can handle so we are playing it safe. Overall the wheelset came in a 1820 grams with the 650B Derby rim in DH layup in 40mm variety. We used Profile Elite hubs and Phil Wood double butted spokes. Our area is very rocky think Santa Barbara or Northstar type rock. These hoops build up very stiff and using them on our Megatrail did transmit more of the trail than other wheels we have ridden in the past.

"The  wider sidewall raises the edge knobs without raising the center knobs, which makes a less round or more "square" tread cross-section profile.

Also the tire casing tension under the edge knobs is increased to be firmer, increasing the tire's stability, and allows lower tire pressure when desired for less rolling resistance over rough terrain from increased bump compliance, and a larger tire patch when weighting the tires while braking and cornering.

Cornering traction is much improved on dusty hardpack to very loose gravelly dirt or loamy covered with leaves, as a result of this combination of flatter tread cross section, stiffer edge knobs, more knobs in contact, and lower air pressure, all enabled with wide  rims.

Changing direction has quicker response with the more stable and firmer structural tire edge with wide rims, without feeling harsh and choppy, and no more sudden washing-out of the front wheel, or as easily skidding the rear tire while cornering.

When the new wave era of trail bikes were "pioneered" in the late '70's until the mid '80's, rims were commonly 35mm to 44mm wide. The  widest tires were 2.1 inches.

In the mid '80's road racers invaded some less challenging mountain bike races to grab pro category purses. But they were not familiar at handling bikes off road. Road racers brought big brand name sponsorship attention, and the race promoters wanted more big budget sponsors involved, so race courses became easier, mostly grass and fire-road race courses so the sponsored road riders could survive mountain bike races without crashing.

Pro road racers knew that climbing was the easier time to gain ground when racing compared to descending. They knew that lighter wheels, less rolling weight, was most important for the climbing advantage. The trend to drop wheel and bike weight was started by these road riders racing on dirt. Aluminum replaced steel frames, handlebars where chopped narrow for weight with much longer reach stems for aerodynamic advantage on faster easier handling race courses.

Keith Bontrager in 1984 cut some 700C (ISO 622) 40-hole Mavic MA-2 tandem rims 27" x 1" rims, re-rolling them to create a 32-hole 26" rims, the first light weight 25mm outer width trail bike rim. Dropping trail bike rim weight from over 600 grams to about 450 grams each, more than 300 grams lighter rolling weight, the most important weight to drop for climbing.

The dominate racers quickly adapted these narrow light rims. Mavic and other rim makers jumped in to make light weight trail bike rims. And the narrow road bike width rims have remained common for trail bikes since this time.

Tires became smaller too, down to 1.8 x 26" and tread was nearly eliminated for the easy mountain bike race courses dominated by road riders from the mid '80's until recent years.

In the mid '90's Downhill was a rapidly growing core mountain rider race format. DH racing grew in spectator popularity due to the much more difficult real tail bike courses, using heavy duty bike frames, now with suspension. A long travel DH bike in the mid to late '90's had 3 inch travel forks and swingarm travel. The lightweight narrow XC rims could not endure the demands of difficult trails. Rims were reinforced and  widened, the added wheel weight was less in performance loss compared to the increase grip and stability for DH speeds, with the Sun Rhyno-lite 29mm  wide  rim leading the  wider rim rebirth.

Most trail riders continue to prefer lighter narrow rims for lower rolling weight enabling quicker climbing, rather than the better handling and greater traction with  wider but heavy aluminum rims. In the recent years, old school trail bike riding re-emerged into popularity, climbing for the rewards of downhill challenges, high speeds, jumps, big rocky drops, and the industry marked this pioneering roots style of riding as something "new" labeling it "AM" or "All Mountain". And bigger volume, more durable "Trail" and "AM" tires became in demand again, but high air pressures are needed to use light narrow rims with larger volume tires.

To better optimize Trail and AM handling requirements in recent years a couple of companies produced 35mm  wide rims. Salsa made a 35mm  wide 29'r rim called the Gordo. A couple years later Velocity, an Australian rim and wheel factory, was commission by Kirk Pacenti to produce a 35mm wide rim to compete with the Salsa Gordo, called the P35. These rims were heavy, nearly 600 grams for the 650b P35, and almost 700 grams for each Gordo 29'r. The Gordo was discontinued. The P35 is still selling well to riders preferring handling performance over climbing speed.

Now, derby rims introduces the world's first 35mm and 40mm  wide carbon fiber rims. Carbon fiber is well proven in aerospace technology and elite motor racing to improve strength, durability, stiffness, but with much lighter weight than other materials. Derby has designed a 35mm  wide 29'r and 40mm  wide 650b rim for advanced trail and mountain riders, having exceptional durability and stiffness, and easy flat tire flat tube repair without needing levers, and a tubeless compatible design that locks the bead next to the rim wall with a floor pump or short compressed air shot of 35psi. At less than 450 grams, very few aluminum rims wider than 24mm XC race rims can a match in weight.

Now without adding any weight you can take the huge leap forward in wheel strength, durability, stiffness, stability, and tire optimization by riding  wide derby rims.

The whole bike becomes more stable on wide rims, feeling like a longer wheelbase bike in directional control but with quicker more positive turn response for more nimble handling and corning grip. Holding a line over loose round rocks though "rock gardens" becomes much easier, without getting kicked side to side when not centered over each loose rock.

The result of going to wide rims with the same tires is immediate increase in confidence while riding loose dusty, gravely, rocky, and wet conditions; enabling higher speeds, harder braking, and more precise and predictable cornering.

With tubeless ready bead seat design, tightly centering the tire around a rim, the upper bead hook is useless, even when using tubes, and weakens a rim, especially carbon rims. The clincher side hooks were useful back when rims had no bead seats for centering the tire around rims as they aired up. Motorcycles don't have bead hooks, cars don't. Have a look at the Specialized Roval carbon rims, they have returned to having no side bead hooks. The side hooks or "clincher" bead hooks, first became used in the early '70s when high pressure inner tubed road tires had trouble centering on the rim when airing up to 65+ psi and would blow off the rim sooner or later. Centering a tire is not a problem now with the tire centering TR inner bead seats now common. And my rim side walls rise 6mm above the bead seat, slightly more than most aluminum rims, also keeping loosely beaded tires on the rims when aired up. These rims can easily take 80psi.

Notice Derby Rims have a bead seat locking "lump" or ridge next to the deep channel around both bead seats. Much like UST bead seat design, this keeps a tubeless bead from sliding inward into the channel and burping while hard cornering. Also the bead locks keep the bead on the bead seat when the tire goes flat, so the flat tire can protect the rim from rock damage while rolling to a stop after flatting. The hookless bead wall with bead seat retention has been used in motorcycle and car tires for decades, but never produced before in bicycle rims design before Derby Rims.

Going to wider rims, the tire's circumference doesn't grow taller. I've closely measured rollout curcumference which calculates to tire height, and measured knob width too. Using the same 2.3 Pacenti neo-moto tire on a 650b x 40mm Derby Rims compared to a 28mm Blunt, the tire doesn't grow taller, the tire is no higher at the center knobs, and the edge knobs are actually a very small measurement narrower, about 0.0225 inch  or 0.6 mm narrower. But the edge knobs do "stand up" a little higher making a more "square" tread profile, and these edge knobs do come closer to the arch of a fork or yoke of a chain-stay by about 1.5mm, so it is slightly closer clearance above the edge knobs."

Finding tires to fit the widest Derby rims will probably be the hardest part. There are some tires that may become to flat or squared off with a 40mm hoop. We would suggest checking to see what others with 35 or 40mm hoops have found to work. We can say is that the Butcher, Salughter, Geax Goma tires worked well and we have heard that the big Trail Kings do also. But we have also heard the High Roller tires do not feel right when mounted to such a wide rim. Another option is to run the 35mm variant to make it a bit less form altering on the tire.

They sealed up easy enough we used gorilla tape and about 4oz of sealant. We used Bead Slip to help get the Specialized Tires mounted up the mounting was pretty easy. Overall the Hookless design of the Derby rims seem to do a good job at holding both the tire and air onto and in the rim. These rims did not seem to burp and we ran pressures in low 20 PSI range a few times on faster smoother trails. We used Uncle Dick's Bead Slip to help get the Specialized tires onto the Derby hoops.

Derby Rim Questions

1. How did Derby Rims come to be?

Established in 2012, derby rims began because Ray, also known as "derby", bought some carbon fiber rims for his trail bike. But he he was very disappointed in the loss in stability and cornering traction compared to the 35mm wide aluminum rims he had been riding. derby liked the much lighter carbon rims for climbing and improved ground tracking from less un-sprung wheel weight . So derby began to design WIDE rims to be made in carbon fiber. And a business was born.

2. What made you decide to go after a wider rim than was currently the norm?

Answered in #1 above.

3. Who is building your rims for you?

An expert manufacturer of carbon-fiber rims in Asia. The name will not be revealed, because I have risked and spent a lot of time, travel, and money to secure my factory.

4. Tell us a bit about your evolution of the Derby rims since the beginning?

See the News page of DerbyRims.com for the significant changes and additions from the start in fall of 2012.

5. What are the dimensions of the Derby rim?

See the specifications of all rims on the “Technical” page of DerbyRims.com

6. What benefits can riders expect to see with a wider rim?

See the “Wide Rims” page, and the Answers to Frequent Questions on the “Technical” page of DerbyRims.com.

7. What tires have you heard are least effected by the wider profile or seem to work well?

All tires 700 x 38C and 2.0 to 2.7 are improved in handling, traction, stability, and rolling ease on rough trail by the 26 and 27.5 x 40mm and 29 x 35mm versions of Derby Rims, there are no exceptions known so far. And 2.2 to 3.5” tires are improved in lighter weight handling response by the 29 x 45mm compared to 29-Plus aluminum rims weighing near 1 pound more, about 50% more, in rolling weight per set. Smaller tires have a greater rate of improvement going to a Derby Rim compared to narrower rims, due to the greater percent of air volume and casing stability increases.

8. Is Derby planning to make thinner versions say maybe a 35/30 or 30/25 variants?

I have drawn designs for narrow paved or hard-pack and gravel ride appropriate rims. I expect a sub-30mm rim for the 700c/29” rim will be produced by Derby Rims, to offer a tubeless ready cyclecross, and disc brake high performance road, and weight-weenie easy trail durable rim, that is under 400 grams in weight.

9. What is the warranty you are currently offering?

See the warranty for all rims on the “Warranty” page of DerbyRims.com

10. What type of trail would you prefer to ride flowing and jump filled or loose and rocky?

I prefer loose and rocky where I must get off and hike my bike because I'm too scared or too weak to ride some sections. Naturally flowy trails are fun too, preferably rocky flowy trails. Artificially built big berm, jump and pump flow trails are fun too, but artificial trails are not a destination when I travel to ride.

11. What is the greatest invention for Mountain Bikes?

The wheel. “Safety-Bike” chain-drive. Nearly all mountain bike technology was adopted from long prior use by motorcycles or automotive such as suspension design and air springs and disk brakes, or from road bikes, such as gear derailleurs and cantilever rim brakes. V-brakes were the first trail bike innovation improving trail bike performance compared to the road bike adapted cantilever brakes. The only other trail bike specific innovation was the “Breeze-Angel Hite-Rite” the first seat-post dropper, much later significantly improved by the remote activated Gravity Dropper and later by other remote dropper posts following with minor technical improvements.

12. Who is the greatest Mountain Biker of all time?

Great ambassador mountain bikers. I can't name just one. The Koski family created the first trail bike shop, the Cove Bike Shop, introducing retail available 3-speed derailleurs in the '60's adaptable to cruiser bikes we used for trail riding then and into the '70's, and they produced the first custom trail bike frames for Mert Lawill, and many components including and motorcycle levers for first uses on trail bikes. More leading trail bike ambassadors and great riders include, Matt Hebberd, Allison Dunlop, Hans Rey, Ned Overand, Tinker Juarez, Juliana Furtado, Tara Lanes, Missy Giove, Marla Streb, Charlie Kelly, Joe Breeze, Scott Nicole.

13. Should they do two Tour De France races and have one that is drug free while the other is anything goes?

No. The modern tests for drugs is much safer for the riders.

14. Anything else you would like to add?

I think the Syntace/Schwalbe ProCore which I am currently testing with Derby Rims with initial success, will enable carbon-fiber rims to become much more durable for DH racing. Obviously, DH racers must expect and budget for frequent equipment failure. Carbon-fiber rims are apparently required to be competitive at the Cat-1 and Pro level of trail bike racing. Failure rates over 15% should be expected each season for any equipment, including expensive carbon-fiber rims and frames. The real pros, paid to train and ride full time for major factories, are the best riders. And to be the best they analyses the course conditions and lines better than others, and ride with flow and precision with nearly no mistakes and with well tuned suspension producing greater speed with less risk of equipment failure. Derby Rims DH options have a durability rate history after one year of availability, statistically equal or better than other available well known brands of carbon-fiber DH rims. A carbon-fiber rim or frame crack is almost never caused by one impact or one ride.

I imagine electric motors will become very popular for DH trail riders where shuttles and summer ski resort DH parks are not readily available. Also more popular for other trails of any kind, not just for DH access. Electric assisted bikes should only be allowed where other motorcycles are allowed. Never on multiple-use trails that allow human powered bicycles. Electric assist bikes are obviously motorcycles, more powerful and heavier than human powered bikes, and so cause much faster damage to trails, enable higher speeds and longer braking distances, and slower handling, and so electric motor assisted bikes are much less safe for all trail users where otherwise only human or animal powered access is allowed.

Thanks for asking!

Ray AKA “derby”

Trevor Roland

The Derby rims in 40mm DH variant weighed 480 grams each. This is a good weight and our wheels built up with strong spokes and nipple came in at a very acceptable number. Our one gripe that was mentioned to us by our wheel builder was that the spoke holes went straight out of the rim instead of going at a slight angle. He was forced to apply pressure to the spokes to get them into the rim holes. Derby has since gone with angeled spoke holes so this is no longer an issue!

Trevor RolandTrevor Roland

Ian W

Overall the Derby rims did what they claim. They allowed us to build up a very stiff wheel with a super wide rim at a very low weight. Having a wheel that offers greater traction, stability, and ride quality just from mounting a standard tire onto a wider rim is plenty of reason for many to try a wide rim like the offering from Derby.

The tires gained noticable traction on the braking front especially when in a straight line. Once the bike was leaned over in a corner it was not really noticeable. What was apparent in cornering and especially rocky terrain was how stiff the wheels where. They are very solid and have little to no detectable give. The wider rims also cut down on burping or loosing air in corners and over hard imapcts. We ended up running a bit lower pressure 28PSI on the back to help soften up the harsh ride over the rocky terrain.

We ran almost the same air pressure as we have in the past with ZTR FLOW EX rims. The Derby rims seemed not to burp like the Stans would at these pressures so that is good. I would probably not feel comfortable running below these pressures in rocky terrain think North Star or Santa Barbara if you are in Santa Cruz go ahead and run 20 PSI in there. But snapping a plastic hoop cause of a hard rock strike just doesn't sound to fun.

Overall these are nice rims that are available in a very wide profile. This can be beneficial for some riders under some instances. I think using the 40mm up front with a 30mm in the rear might be the best route to go for trail riding or DH riding. The 40mm in the back of the bike will limit tire choice.

Conclusion

Wide rims have advatages and disadvantages. They do offer more traction in straight lines and with the right tires with a rounded profile even in the corners. They allow lower PSI to be run than a smaller width rim and seem to not burp at all. As it stands now the tire choice for the widest rim is the disadavtage. You do not want to run 2.2 tires with a square profile. We ran a Butcher 2.35 up front and it seemed okay but we did loose some edge bite with such a wide rim profile under it.

I would take a look at the tires you like to run. If you like running tures that are 2.2 and thinner you don't want to run wide rims. I would suggest 25-30mm ID as a ballpark. The next wheels we build will probably be in that range for the Enduro bike.

These wheels build up stiff so for riding that will use bigger tires and a stiff wheel is needed we would suggest taking a look at what Derby has to offer.