Derby Carbon DH 40I Disc Rim
The Derby DH 40i is the widest rim the maker offers in its heavy-duty layup: 39.5mm inside for 2.8 to 3.0in tires, hookless 3mm-thick walls and tubeless retention ridges, with more carbon at the bead and spoke bed and a 300lb rider rating. Made in the USA by a small shop who pioneered wide carbon mountain rims, it is the rim for plus-tire e-bikes, heavy riders on plus bikes and anyone who wants a 40mm carbon rim that will not break.
This page covers the Derby Carbon DH 40I Disc Rim in 29in, 27.5in. The Derby DH 40i is built to order here. Choose the hub, spokes and nipples in the configurator; the wheel leaves Georgia laced, tensioned and trued.
Design and construction
The rims are simple in the way good carbon rims are: a shallow hookless section with walls thick enough that a rock strike squeezes the tire rather than cutting it, a bead seat with a retention ridge that keeps a tubeless tire on at 18 psi, and a layup that puts the carbon where the loads are. The 30i takes 2.0 to 2.3in tires happily and 2.6in tires without complaint. The TR layup is for trail and all-mountain; the DH layup adds material for enduro and downhill and is rated for riders up to 300lb.
How it rides
A Derby DH 40i wheel with a 3.0in tire floats and grips like a plus wheel should and takes the hits a heavy rider or an e-bike produces without complaint. It is heavier than the TR 40i and far lighter than any alloy rim of its width. For 2.6in tires the DH 35i is lighter; for 2.8 to 3.0in on an e-bike or under a heavy rider, the DH 40i is the Derby rim we recommend.
Specifications
| Wheel size | 29in, 27.5in |
|---|---|
| ERD | 584 (29in), 540 (27.5in) |
| Inner width | 39.5 mm |
| Drillings | 32h |
| Weight | 565g (700c/29in), 560g (650b/27.5in) |
| Material | Carbon Fiber |
| Tire type | clincher tubeless compatible |
| Brake | Disc |
| Profile | Triangle |
| Nipples | External |
| Finishes | black |
Which version this is
What this listing covers: the DH 40i in 29in, 27.5in with 32h drilling, about 565g, 39.5mm inside, mm deep, disc. If you need it in another size or for the other brake type, it is listed separately.
This is the disc-brake DH 40i: plain sidewalls, no brake track to wear, a touch lighter. It fits any disc-brake bike and it is the version most of our customers now build; the rim-brake version is a separate listing.
Sizes, fit and compatibility
The Derby Carbon DH 40I Disc Rim comes in 29in, 27.5in and 32h drilling. It is a disc-brake rim. We build the DH 40i on Industry Nine Hydra 2, DT Swiss 350, Hope Pro 5 and Onyx Classic hubs in Boost spacing, usually with Sapim Strong or Race spokes or DT Alpine III and Competition, and brass nipples.
Tire range on the DH 40i is 2.8 to 3.0in, tubeless-ready tires only on the hookless bead. Pick plus or e-bike as your bike type in the configurator and it recommends a spoke count and lacing pattern.
Build it into a wheel
This rim is live in our Custom Wheel Program for mountain bike, MTB single-speed and fat bike builds. Start a build with the DERBY CARBON DH 40i DISC RIM and the configurator opens with this exact rim pinned at the top of the Derby list — you choose the rest of the parts and it validates every combination as you go.
Spoke head is decided by the hub, not the rim: this rim builds equally well with J-bend or straight-pull spokes, and the configurator only offers the spokes that match the hub you pick.
Derby's testing and certifications
Derby Rims, based in Utah, designs its carbon rims in the US and has a partner factory in Asia make them; Derby states its rims were the first carbon rims strong enough for aggressive mountain bikers when it started in 2012. Derby publishes no laboratory impact or fatigue figures; it relies on ride testing. Derby states the Sol Rider line was tested by dozens of extreme MTB riders over 3 years with zero failures, including DH and Enduro racing and 35 foot gap jumps from 2018, and that the first Sol Rider was cracked in 2023 after more than 5 years. The Sol Rider uses Derby's Solstice layup, alternating a US-designed plastic composite fiber UD with UD carbon fiber; Derby states the plastic layers stretch under hard impacts to stop micro-fracturing, and that it was first with 3 mm thick hookless rim walls and bead seat retention ridges.
Derby's published limits: recommended rider weight 175 lbs / 90 kg for XC (CX and BX) rims, 225 lbs / 100 kg for xc.Trail and 300 lbs / 135 kg for enduro.DH rims; max spoke tension 125 KgF; max mountain tire pressure 32 psi for road use, 22 psi for 2.6 in and larger tires, 30 psi for enduro/DH race, park and shuttle; bead seating 35 to 40 psi; 44 mm minimum valve stem.
Certifications
- Warranty — Lifetime warranty to the original owner: first replacement free within 5 years of purchase, subsequent replacements 50% off MSRP; secondary owners 50% off MSRP warranty/crash replacement regardless of age; receipt, photos and serial number required (source)
Sources on Derby's site:
- Derby Rims - Rim Specs
- Derby Rims - Sol Rider
- Derby Rims - History
- Derby Rims - Terms, Warranty, Returns
- Derby Rims - FAQ
Everything in this section is published by Derby. ProWheelBuilder is the wheel builder, not the tester, and the rim reaches us as the maker ships it.
Building it at ProWheelBuilder
Derby makes the DH 40i; ProWheelBuilder is an independent wheel builder in Georgia, not the manufacturer. The build is the same every time: measured ERD, spokes cut to the half millimeter, staged tensioning with a gauge, stress relief, a final true, and tubeless tape and a valve on request.
The configurator shows only hubs and spokes that match the DH 40i drilling, strikes through combinations that are not made, and prices the wheel live.
Warranty
Manufacturer's warranty. Derby warrants this product against defects in materials and workmanship. The duration, conditions and claim process are set by Derby and can change without notice, so ask us and we will confirm the current terms before you buy.
ProWheelBuilder. Any wheel we build on this part carries ProWheelBuilder's one-year warranty in addition to the manufacturer's. Broken spokes are replaced for a year whatever the cause, and all wheel-side labor is included - truing, re-tensioning, rebuilding. Where the maker covers a failed rim or hub we handle that claim for you; where they decline, an eligible replacement comes at 25% off current retail. The customer covers shipping in both directions. Components supplied by the customer are not covered.
Full terms are on our Policies & Warranty page.
Carbon DH 40I Disc Rim questions
What tire width suits this rim?
At 39.5mm inside this is a plus or fat width, for tires from about 2.6in upward. Running a narrow tire on a rim this wide leaves the casing stretched and vague, so match it to the tire it was designed around.
Which spokes and nipples suit the DH 40i?
For most riders a double-butted spoke such as Sapim Race or DT Competition with brass nipples; lighter riders can go to Sapim Laser or CX-Ray. The configurator recommends a gauge and count for the DH 40i from your bike type and weight.
DH or TR layup?
DH for enduro, downhill, park, e-bikes and riders over about 200lb; TR for trail and all-mountain where its lighter layup is plenty.
Is ProWheelBuilder the manufacturer of the Derby Carbon DH 40I Disc Rim?
No. The rim is made by Derby; we are the wheel builder in Georgia who laces it into a finished wheel to your spec and stands behind the build.
Is it tubeless-ready?
Yes. Derby lists the Carbon DH 40I Disc Rim as clincher tubeless compatible; we tape and fit a valve when you choose the tubeless option.
Which spoke count should I choose?
It depends on your weight, terrain and the hub, not the rim alone. The configurator recommends a count from your bike type and rider weight, within the drillings this rim is made in.
How long will the wheel take?
Build time comes down to parts availability rather than bench time. The estimated ship date is shown in the configurator before you check out.
Not sure? Text or leave a voicemail on 470-253-0929 or email info@prowheelbuilder.com — you will be talking to the people who build the wheels.
