Derby Carbon BX 25I Disc Rim
The Derby BX 25i is the gravel and cyclocross rim from the small American maker of thick-walled carbon rims: 25mm inside, 32mm deep, about 430 grams, made in the USA from unidirectional carbon with hookless walls 3mm thick and tubeless retention ridges, disc only. It is the same profile as Derby's CX 25i and brings Derby's rock-proof construction to a 700c rim for 33 to 45mm tires.
This page covers the Derby Carbon BX 25I Disc Rim in 27.5in. The Derby BX 25i is not sold bare. You choose the hub and the rest of the build in the configurator, and it ships from our shop in Georgia laced, tensioned and trued by hand.
Design and construction
The CX 25i is a 32mm-deep hookless carbon rim with 3mm-thick walls that squeeze a tire on a rock strike rather than cutting it, a bead seat with a retention ridge that keeps a tubeless tire on at cyclocross pressures, and a 25mm inner width that suits 33 to 45mm tires. The depth gives the wheel lateral stiffness and a hint of aero without the weight of a road aero rim. It is molded in the USA, in 32 hole, disc only, for standard J-bend spokes and external nipples.
How it rides
A Derby CX 25i wheel is stiff, tough and quick. The 32mm section holds a line through a rutted corner, the thick walls shrug off the rocks that dent alloy gravel rims, and the 23mm bed keeps a 40mm tire stable at low pressure. It is not the lightest carbon gravel rim; it is one of the toughest. For gravel racing and cyclocross on rough courses, the CX 25i is the Derby rim we recommend.
Specifications
| Wheel size | 27.5in |
|---|---|
| ERD | 540 (27.5in) |
| Inner width | 25 mm |
| Depth | 32.5 mm |
| Drillings | 28h, 32h |
| Weight | 415g (650b/27.5in) |
| Material | Carbon Fiber |
| Tire type | clincher tubeless compatible |
| Brake | Disc |
| Profile | Triangle |
| Nipples | External |
| Finishes | black |
This listing
This is the 27.5in listing of the BX 25i, 28h, 32h, about 415g, 25mm inside, 32.5mm deep, disc. Pick the size that matches your frame; the profile and construction are the same across the range.
This is the disc-brake BX 25i: 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 BX 25I Disc Rim comes in 27.5in and 28h, 32h drilling. It is a disc-brake rim. We build the CX 25i on Industry Nine SOLiX and 1/1, DT Swiss 350, 240 and 180, White Industries CLD, Chris King R45 and Hope RS4 hubs, usually with Sapim CX-Ray, D-Light or Race spokes or DT Aerolite and Competition, and brass nipples.
Tire range on the CX 25i is 33 to 45mm, tubeless-ready tires only on the hookless bead. Pick gravel or cyclocross 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 gravel and road disc, mountain bike, MTB single-speed and fat bike builds. Start a build with the DERBY CARBON BX 25i 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.
What Derby says about testing
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
The figures, certificates and media above are Derby's own. ProWheelBuilder does not run these tests; our part is the wheel we build on the rim.
Building it at ProWheelBuilder
Derby makes the BX 25i; ProWheelBuilder is an independent wheel builder in Georgia, not the manufacturer. Every BX 25i wheel we build gets spokes cut from the rim's measured ERD, is tensioned in stages with a gauge, stress-relieved and trued before it ships. Tubeless tape and a valve are fitted on request.
In the configurator you will only see parts that fit this drilling; combinations that are not made are struck through, and the price updates as you pick.
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. Our one-year wheel warranty applies to any wheel we build around this part, alongside whatever the manufacturer offers. Inside that year, broken spokes are replaced no matter how they broke, and the wheel labor is ours - truing, re-tensioning or a full rebuild. A rim or hub failure that the maker covers, we claim for you and see through; one the maker declines, we answer with an eligible replacement at 25% off current retail. Shipping both ways is yours, and components you supply yourself fall outside this cover.
Full terms are on our Policies & Warranty page.
Carbon BX 25I Disc Rim questions
What tire width suits this rim?
25mm inside is the all-road and gravel width. Think 32 to 45mm tires: wide enough to support a gravel casing properly so it holds its shape at low pressure, narrow enough that a 30mm road tire still sits right if you swap wheels between bikes.
Which spokes and nipples suit the BX 25i?
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 BX 25i from your bike type and weight.
Is the CX 25i hookless?
Yes. Use tubeless-ready tires and stay under the maximum pressure printed on the rim, which for a gravel tire is well above what you would run anyway.
What tires fit the CX 25i?
33 to 45mm. A 38 to 42mm gravel tire or a 33mm cross tire is the usual pairing.
CX 25i or BX 25i?
The same 23mm-inside, 32mm-deep rim; BX and CX are the maker's naming for different production runs of the same profile. Pick by availability.
Are these rims made in the USA?
Yes. Every rim is molded in the USA in small batches.
Is it tubeless-ready?
Yes. Derby lists the Carbon BX 25I Disc Rim as clincher tubeless compatible; we tape and fit a valve when you choose the tubeless option.
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.
