Derby Rims Leads Bicycle Rim Design

In 2012 Ray aka "derby", began drawing a new design for his first carbon-fiber mountain bike rim. This is the story of innovation in Derby Rims design to solve all the existing mountain carbon-fiber rims very poor durability problem, and the easy burping of tubeless tire conversion problem. Also by late 2014 he solved the problem of rapid alloy nipple corrosion when used in carbon-fiber rims.

Ray was aware of actual problems of rim durability with the existing brands of carbon-fiber rims offered for mountain biking uses in 2012. It should be noted that mountain bike rims are the most impact exposed intended use of carbon-fiber ever. Only super-sonic high speed aerodynamic vibration of the wings of stealth jets or rockets may have more exposure to carbon-fiber damage than mountain bike uses. Yes, Formula-1 and other carbon-fiber race cars shatter parts upon the slightest impact, but they are not intended for impact! 

Also tubeless converted tires were becoming more established use for mountain bikes in 2012, and rim-strip and sealant kits were available commercially. But Ray experienced frequent burps and burp-flats and almost gave up on tubeless until using a “ghetto-tubeless” split inner-tube as a rim-strip, which effectively bonded to the tire's bead with sealant and the inner-tube moved with the sliding tire beads somewhat like a tubular tire, eliminating burps. But reliable tire flat prevention using  “ghetto-tubeless” was nearly double the weight of only a tube.

The first major improvement was in durability, by improving upon a pre-1970's hookless rim wall design by increasing wall thickness to 3mm, which greatly improved sharp hit durability and improved resistance to excessive rim flex. Flex, excessive flex, is what causes damage to carbon-fiber. Derby Rims were immediately 3 to 5 times more durable than any other carbon-fiber mountain rim available in 2013 when introduced, according to early test riders and pro category racing customers already familiar with many of the other 5 or 6 brands of carbon-fiber mountain rims in existence in 2013. And no other rim has yet become half as durable as Derby rims, except some of the very heaviest aluminum rims. By far, most of the first issue 2013 rims have never been damaged, other than scrapes and scuffs.

Also Ray had always had problems with tubeless tires with sealant frequently burping, even suffering sudden burp tire flats when hard cornering. He had noticed some motorcycle racing tires had bead seat ridges next to the deep center channel, and he thought that the bead retention ridges could improve tubeless use of mountain bike tires to prevent the tire bead from sliding into the deep center channel causing a burp. And he added 0.5 mm retention ridges to the first Derby rim design. Previously only Mavic's patent protected UST rims had retention ridges in combination with rim wall hooks to form a bead socket with Mavic UST specification tubeless tire beads. The Derby Rims thick hookless rims with bead seat retention ridges worked perfectly to eliminate burps  for tubeless tires with sealant. And the retention ridges added much safety by retaining tire beads when a tire goes flat, protecting the rim from damage and preventing the flat tire from dropping off the rim possibly locking the wheel.

Form follows function in Derby rim design. All Derby rims have parabolic shaped rim walls profile when viewed in cross-section. Parabolic structures are the strongest load bearing shape in existence. Stronger than round, or “U”, or “I-beam”, or squared, or triangular shaped structures and rim walls. Some road rims had previously used parabolic shapes, claiming to produce improved aerodynamics which is so important for long fast road riding efficiencies. No mountain rim before Derby Rims design had utilized parabolic rim profile. 

Since Derby Rims became publicly revealed and available for purchase in August 2013, nearly all  existing and new brands of mountain rims have very closely copied the leading design improvements introduced by Derby Rims. Even nearly every new model of aluminum rims for tubeless tire use now have copied Derby Rims leading design of bead retention ridges.

In late 2014 all new Derby rims also had water drain holes, never before documented as a feature of production rims by any other brand, although a few rims had aftermarket experimental drain holes drilled. Water can fill a hollow “double-wall” rim, accessing past the nipples when washing or riding through a creek or in the rain. Without drain holes near the edge of the rim, water will be trapped for many months, unable to drain up past the nipples. Also trapped water adds an ounce or more to the rim weight. Alloy nipples in carbon-fiber rims with corrode rather quickly in months with water is trapped inside. Aluminum hollow rims also trap water for many months, but the aluminum of the rim shares the galvanic-corrosion rate with alloy nipples, so the alloy nipple corrosion is many times slower in aluminum rims no having drain holes. 

Derby Rims filed patent applications for these original bicycle rim design leading innovations, mainly for self-protection in case another rim brand copied Derby Rims design and was able to patent the copied design, and legally force Derby Rims to pay to license or cease using his own original designs.

Photo above is courtesy from authorized wheel builder Mike Curiak of Big Wheels, Grand Junction, CO

The WIDE RIM Revolution!
optimizing the performance of mountain tires since 2012

optimizing the performance of road and gravel tires since 2016

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 climbing and pedaling over rough technically difficult 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 slightly 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.

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 sliding off round rocks or 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. Riders report their Strava times immediately improve going to Derby Rims, with the same tires and bike, and times continue to improve further as confidence is gained with the much increased traction while climbing, cornering, and descending.

WIDE RIMS are not new
A brief history:

When the new wave era of trail bikes were "pioneered" in the mid '70's until the mid '80's, rims were commonly 35mm to 44mm outside wide, and 5mm less inside. 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. Only in the recent years has XC racing become more like the early mountain bike races including rocky and rooty obstacles. XC racing is now AM racing again.

Pro road racers knew that climbing had the most 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 lighter weight with much longer reach stems for climbing and pedaling 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 mountain bike rims. Dropping trail bike rim weight from over 600 grams to about 450 grams each, more than 350 grams lighter rolling weight per rim, the most important weight to drop for climbing and acceleration.

The dominate racers quickly adapted these narrow light rims. Mavic and other rim makers jumped in to make light weight mountain bike rims. And the narrow road bike width rims have remained common for trail bikes since that time.... until Derby Rims lead a light-weight wide carbon-fiber rim revolution!

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 full-suspension. A long travel DH bike in the mid to late '90's had 3 inch travel forks and swing-arm 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 outside width 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. Around year 2000, old school mountain 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  outside width 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 outside width rim to compete with the Salsa Gordo, called the P35. These rims were heavy, 600 grams each for the 650b P35, and almost 700 grams for each Gordo 29'r. The Gordo was discontinued. The P35 was renamed the Blunt-35 and is still selling well to riders preferring handling performance over climbing speed.

In summer 2013, Derby Rims introduced 35mm '30i' and 40mm '35i'  wide carbon fiber rims, the world's first carbon rims wider than 30mm outside width. 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's first rims were a 35mm 30i wide 29'r and 40mm '35i' wide 650b rim for advanced trail and mountain riders, having exceptional durability and stiffness, and easy flat tire removal by hand for 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 35 to 40 psi. In 2014 40mm '35i'wide 26" rim were introduced, also DH layup versions of the three wheel rim sizes. In 2015 a 45mm '40i' wide 29'r Derby rim was introduced, the widest carbon 29er rim available and world's first 29 Plus rim. In 2016 a 50mm '45i' wide 27.5 Derby rim was introduced optimized for 27 Plus and "B Fat" tires.

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. And compared to aluminum rims just as wide, large chunks of rolling weight pounds are dropped going to Derby Rims.

Since 2012 ... The Highest Performance & Most Durable Carbon Fiber Rims for MountainRoad, Gravel, Adventure & E-Assist Bikes

HAND MADE, labor intensive

Carbon rims are expensive to produce. They require many hours of skilled labor cost compared to aluminum rims, and many times the materials cost. Each carbon fiber steel mold is CNC machined for many days to finish, about 1 week of machining per rim. In China the carbon fiber costs about $40 per rim. Then to produce rims requires big machines to pump and vacuum the inner bladder and heat the very heavy steel molds, then after cooling the mold, pop the rough rim out and hand file and sand the resin creep while in the mold, holes are drilled, and then finish painted, before QC inspection and finally packing for shipment. The Derby Rims factory has 24 QC sign-offs during production of each rim.

In contrast, aluminum rims are machine made, from raw metal bars fed into a machine and pinched into shape in metal rollers. Then the rolled aluminum is machine pinned and welded, holes drilled, and finish painted, rarely touched by hands except to stack the raw metal bar onto the machine, transferring to the hole machine, then moving to the paint booth, before packing for shipment, and the customer or wheel builder does the QC for aluminum rims.

Each carbon fiber rim costs 6 to 8 times more in labor and materials than an aluminum rim.

Why Derby Rims vs. other carbon fiber rims?

Ray AKA 'derby', the designer and producer of Derby Rims, has been asked, "Why Derby Rims vs. other carbon fiber rims?" Here are many great reasons to ride Derby rims vs. any other carbon fiber rim option.

- Mountain biking guru Keith Bontrager once came up with the moto: 'Cheap, light, durable - pick two.' ...However, with Derby Rims, pick all three!

- Derby Rims are the lowest priced US designed and supported carbon rims. Yes, there are lower priced aluminum rims or direct mail order carbon rims from China web-store merchants, but Derby Rims leading durability and quick US based customer support when rare damage occurs also matters in the long run.

- Derby Rims are light in weight. Far lighter in weight than aluminum rims at similar widths. Also lighter than some of the other more expensive carbon rims following Derby Rims leading design with near the same rim widths. Narrower carbon rims can be more than a few grams lower weight, but narrow rims are a huge performance sacrifice, slower climbing, slower rolling, poor braking and cornering, and less stability. And a few grams of weight difference to other wide carbon rims is a very minor factor when considering the next major factor advantage of Derby Rims, durability.

- Derby Rims are the most durable, at any price, as reported by many authorized dealers and Pro and Elite category championship winning racers riding Derby rims, who are well experienced with many other carbon rim options. Less than 1% damage was reported of all Derby rims in 2017, of more than 8000 rolling. Elite/Pro category Enduro and DH carbon rim riders report that other carbon rims failed in the same race and training conditions well over 20% rate, many over 50% fail rate per racing season. The Derby 27.5 AM trail rim was under 1% rate in 2017, and the DH/FR was just under 1% rate in 2017. All the 29er Derby rims are well under 0.5% damage rate, apparently the larger wheels roll the same obstacles more smoothly, or flex less excessively than the smaller wheels when hit sharply. Some models have never been reported damaged, including the CX, RC, and RD road rims sin introduction in early 2016. I wish there was 0% damage, but mistakes and bad luck does happen. Compared to Derby carbon rims, aluminum rims have a much higher rate of damage where replacement is required. The durability advantage is due to the industry leading Derby rim design, not by added weight.

- Derby Rims design introduced thicker hookless rim walls to carbon rims, increasing durability by an exponential magnitude. Nearly all hookless carbon rims designed by other brands afterwards have closely copied the Derby Rims designed thicker rim wall.

- Derby Rims design includes the most durable parabolic rim profile. A parabolic structure supports load and impact-force inputs at all angles far greater than any other rim profile design. A parabolic rim profile, for given materials and layup, is more durable for load inputs compared to rim profiles that are ‘U’ shaped, ‘triangular’, ‘I-Beam’, round, square or rectangular or other multi-faced profiles.

- Derby Rims design introduced the first bead seat retention ridges to hookless rims. Previously, only the 1999 Mavic UST (Universal Standard Tubeless) design had a similar bead seat ridge in the hooked rim specific UST system. Nearly all hookless carbon and aluminum rims designed by other brands have closely copied Derby Rims design with bead seat retention ridges.

- Derby Rims introduced the first ever documented water drain holes to production bicycle rims. The water drain holes quickly eliminate water trapped inside hollow rims when water is easily able to enter through the rim spoke holes past nipples while washing wheels, riding through deep streams, or riding in the rain. Otherwise, nearly an ounce of water remains trapped inside any hollow rim with spoke holes for many months. In carbon rims, trapped water inside the rims enables galvanic corrosion of aluminum alloy nipples, producing rapid alloy nipple failure. Aluminum rims share in corrosion with alloy nipples, so the problem of nipple corrosion failure is not so rapid in aluminum rims as the problem is for carbon rims when water is retained inside hollow rims.

- Improvements in both traction and rolling resistance and bike handling feel are noticeable when going to wider and stiffer Derby rims. Riders of Derby rims report they immediately break all their Strava speed and time interval records, while climbing and descending and all timed interval conditions, only by upgrading to Derby rims on the same bike from narrower rims. And they continue to break their new Strava records on Derby rims, as they gain confidence in the much improved climbing traction, to be able to pedal harder without spinning out, as well as cornering and breaking harder with the added traction. And negotiating rocky or rooty and irregular trail with much improved stability and improved handling feel of traction limits and directional control. Rolling resistance is noticeably reduced, conserving rider energy and enabling more speed, with the lower tire pressures enabled with wider rims using the same favorite tires.