WTB KOM Tough TCS I 25 Rim
The narrow end of WTB's KOM Tough range: 25mm inside, welded alloy, and the same TCS tubeless bead and 4D angled drilling as its wider siblings. The i25 is the one to pick when you want KOM Tough's wall thickness under a cross-country or light trail tire rather than a 2.6in trail casing. WTB design and manufacture the rim; ProWheelBuilder is an independent wheel builder in Georgia, not the manufacturer.
We sell it as a finished wheel: choose the hub, spokes and nipples and we lace, tension and true it by hand here.
Design and construction
KOM Tough is the heavier of WTB's two KOM layups — thicker walls than the KOM Light for the same profile — and the i25 is the narrowest section they make it in. TCS stands for Tubeless Compatible System, WTB's bead profile that seats a tubeless tire with a floor pump and holds it at low pressure. 4D drilling angles each spoke hole toward the hub flange it serves, so the nipple sits straight and the spoke is not bent where it leaves the rim, and an I-Beam web inside the section stiffens the spoke bed.
It is a welded joint rather than a pinned one, which is the more expensive way to close an alloy rim and the reason the bead diameter stays even all the way round.
How it rides
At 25mm internal the i25 supports roughly 2.1 to 2.4in cross-country and light trail tires without the sidewall folding in hard corners, and it does it with more material in the spoke bed than a climbing rim would carry. In our strength model it scores 4.55 out of 10 — lower than the wider KOM Toughs simply because there is less section there, and a figure worth reading against the other rims in the configurator rather than on its own.
The practical case for it is a rider who has dented lighter XC rims and wants the tougher layup without moving up to a 30mm inner width they do not need.
The CVX generation
These are the current TCS 2.0 w/CVX version. Two things changed from the rim WTB built before it. CVX is a patented spoke bed that, in WTB's words, strengthens it “without increasing weight, by thickening material where it's needed and removing where it's not” — so the material sits around the spoke holes, where an alloy rim actually cracks. TCS 2.0 adds a Solid Strip fitted under the tubeless tape, which makes seating and sealing a tubeless tire less fussy. WTB publishes a maximum spoke tension of 110–120 kgf for this rim, which is the figure we build to.
Specifications
| Wheel size | Inner width | Outer width | Depth | ERD | Weight |
|---|---|---|---|---|---|
| 29in / 700c | 25mm | 29.5mm | 20mm | 603 | 478g |
| 27.5in / 650b | 24.5mm | 29.3mm | 17mm | 567 | 450g |
32 hole, disc brake only, hooked bead, external nipples, aluminum. The ERD figures are the ones we cut spokes to.
About this listing
This is the rim on its own, as a component of a hand-built wheel. Pick the diameter above and we build the wheel around it.
Sizes, fit and compatibility
Available in 29in and 27.5in, 32 hole, disc brake only, for external nipples.
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.
Put it in a custom wheel
Build a custom wheel around the KOM Tough i25 and the configurator opens with this rim pinned at the top of the WTB list, ready for you to choose the hub, drilling, spokes and nipples. It validates every combination as you go, so you cannot assemble a wheel we would not build.
How WTB tests its rims
WTB (Wilderness Trail Bikes, California) builds its rims around the TCS tubeless system. WTB states the Beadlock bead profile is "Designed to ISO/ETRTO standards", that 4D drilling angles each spoke hole toward the hub flange, and that most alloy rims are sleeve-jointed, the rim ends hydraulically pressed over an extruded aluminum insert reinforced with industrial epoxy. KOM and HTZ rims use 6069 aluminum for its "high tensile and fatigue strength"; HTZ e-bike rims add 20% wall thickness over KOM Tough.
Published limits: maximum spoke tension 110-120 kgf on KOM, HTZ and CZR rims; max rider weight 265 lbs for the CZR i23 and 300 lbs for the CZR i30. No per-rim maximum tire pressure is published and no ISO 4210 or UCI certification is claimed.
Testing: WTB states the CZR carbon rims went through hundreds of rims, dozens of layups, three rounds of rider testing and nearly a year on the final design without a broken rim. WTB also states it sent CZR rims to "an unbiased third-party lab" for destructive testing against competitor carbon rims, finding the CZR i23 "38% more impact resistant than their direct competition" and the CZR i30 "10% more impact resistant." The lab is not named.
Warranty: WTB guarantees its products "for at least two years"; Ci24/Ci31 carbon 36 months. CZR carbon rims carry a Limited Lifetime warranty for the original owner plus the Ride With Confidence Guarantee: a CZR broken while riding is replaced free with a free rebuild; one damaged while not riding is replaced at 50% off current MSRP.
WTB's videos
Certifications
- ISO/ETRTO bead design — WTB states its TCS Beadlock profile is "Designed to ISO/ETRTO standards" and CZR TCS 2.0 is ETRTO/ISO compliant (source)
- CVX spoke-bed technology — Stated as patented by WTB (source)
Sources on WTB's site:
- Rim Technology - WTB
- Warranty - WTB
- Ride With Confidence Guarantee - WTB
- CZR i23 Rim - WTB
- CZR i30 Rim - WTB
Everything in this section is published by WTB. ProWheelBuilder is the wheel builder, not the tester, and the rim reaches us as the maker ships it.
Building it at ProWheelBuilder
Spoke length comes from the measured hub and this rim's real ERD — 603 in 29in, 567 in 27.5in — rather than a catalog average, so the nipples end up seated properly instead of running out of thread. Every wheel is laced, tensioned and trued by hand in Georgia, and we check tension round the wheel rather than trusting a single reading.
Labor is included in the wheel price. Tubeless tape and valves are an option at build time.
Warranty
WTB's warranty. WTB's cover depends on the rim: CZR and CGR carbon rims carry a limited lifetime warranty to the original owner, Ci24 and Ci31 carbon rims three years, and every other rim 24 months, all against defects in material and workmanship. A CZR rim broken while riding is replaced free; damage from a non-riding incident is replaced at half the current list price. Claims must be raised within 60 days of finding the defect.
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.
KOM Tough TCS I 25 Rim questions
How is the i25 different from the i30?
Width, mostly. The i25 is 25mm inside against the i30's 30mm, so it suits narrower tires and comes out lighter — 478g against the i30's 538g in 29in. Both use the same KOM Tough layup, the same TCS bead and the same 4D drilling.
Why pick KOM Tough over KOM Light at this width?
Thicker walls. KOM Light is the same profile with less material, so it is lighter but less tolerant of rock strikes. Pick Tough if you have dented rims before or ride loaded.
What tires fit?
At 25mm internal, roughly 2.1 to 2.4in cross-country and light trail tires. Narrower than about 2.0in starts to square off on this width; much wider than 2.4in would be better served by the i30.
What is the ERD, and why does it matter?
603 in 29in and 567 in 27.5in. It is the measurement spoke length is calculated from — get it wrong by a couple of millimeters and the spokes either bottom out in the nipple or leave thread showing.
Can I have straight-pull spokes?
Yes. Spoke head is set by the hub you choose, not by the rim, and the configurator only offers spoke brands that match it.
Is it tubeless-ready?
Yes — TCS is WTB's tubeless bead system, and the rim seats a tubeless tire with a floor pump. We tape it and fit a valve when you choose the tubeless option.
Rim brake or disc?
Disc only. There is no machined braking surface on the sidewall.
What drilling is available?
32 hole in both sizes. That is the count the strength figure and the lacing recommendations in the configurator are based on.
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.
