WTB KOM Tough TCS I 40 Rim
The WTB KOM Tough i40 is the plus-tire rim in the KOM Tough family: 40mm inside for 2.8 to 3.0in tires, with WTB's TCS tubeless bead, 4D angled spoke drilling and I-Beam center support in the heavier Tough layup. It is the alloy rim for 27.5+ and 29+ bikes that need a wide, tough, sensibly priced wheel.
This page covers the WTB KOM Tough TCS I 40 Rim in 29in, 27.5in. The KOM Tough i40 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
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; the KOM Tough needs 35mm TCS tape and a WTB valve, which we fit. The I-Beam is a vertical web inside the rim section that stiffens the spoke bed, and 4D drilling angles each spoke hole toward the hub flange it serves so the nipple sits straight and the spoke does not bend at the rim. The KOM Tough is a welded 6069-class alloy rim with thicker walls than the KOM Light for the same profile.
How it rides
A KOM Tough i40 wheel with a 3.0in tire floats over roots and rocks and grips on loose climbs, and the 40mm bed keeps the big tire stable at the 12 to 15 psi that makes plus riding work. The welded rim and 4D drilling keep the wheel true under the abuse a plus bike sees. It is a heavy rim, as every 40mm alloy rim is, and on a plus bike that is the right trade.
For 2.6in tires the KOM Tough i35 is lighter; for 2.8 to 3.0in, the i40 is the WTB rim we recommend.
Specifications
| Wheel size | 29in, 27.5in |
|---|---|
| ERD | 606 (29in), 568 (27.5in) |
| Inner width | 40 mm |
| Depth | 16.5 mm |
| Drillings | 32h |
| Weight | 653g (700c/29in), 611g (650b/27.5in) |
| Material | Aluminum |
| Tire type | clincher tubeless compatible |
| Brake | Disc |
| Nipples | External |
| Finishes | black |
This listing
This is the 29in, 27.5in listing of the KOM Tough i40, 32h, about 653g, 40mm inside, 16.5mm deep, disc. Pick the size that matches your frame; the profile and construction are the same across the range.
This is the disc-brake KOM Tough i40: 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 WTB KOM Tough TCS I 40 Rim comes in 29in, 27.5in and 32h drilling. It is a disc-brake rim. We build the KOM Tough i40 on DT Swiss 350, Industry Nine 1/1 and Hydra 2, Hope Pro 5 and Bitex BX 211 hubs in Boost spacing, usually with Sapim Race or DT Competition spokes and brass nipples.
Tire range on the KOM Tough i40 is 2.8 to 3.0in. Pick plus 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 MTB single-speed, mountain bike and fat bike builds. Start a build with the WTB KOM Tough TCS I 40 Rim and the configurator opens with this exact rim pinned at the top of the WTB 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 WTB says about testing
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.
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.
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.
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
WTB makes the KOM Tough i40; ProWheelBuilder is an independent wheel builder in Georgia, not the manufacturer. Every KOM Tough i40 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
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. Wheels we build around this part are covered by our own one-year warranty alongside the maker's. Within the year: broken spokes replaced regardless of cause, and the labor on the wheel - truing, re-tensioning or a complete rebuild - included. A manufacturer-covered rim or hub failure is a claim we make and manage for you; one they will not cover is answered with an eligible replacement at 25% off retail. Shipping each way is yours. Parts you supply yourself fall outside it.
Full terms are on our Policies & Warranty page.
KOM Tough TCS I 40 Rim questions
What tire width suits this rim?
At 40mm 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 KOM Tough i40?
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 KOM Tough i40 from your bike type and weight.
KOM Tough or KOM Light?
Same profile. Tough has thicker walls for trail and all-mountain; Light saves about 60 grams for cross-country. We stock the Tough.
What does TCS mean?
Tubeless Compatible System, WTB's bead shape that seats and holds a tubeless tire; it needs WTB TCS tape, which we fit.
Which KOM Tough width should I choose?
i25 for 2.2 to 2.4in cross-country tires, i30 for 2.4 to 2.6in trail tires, i35 for 2.6 to 2.8in, i40 for 2.8 to 3.0in plus tires.
Is the KOM Tough e-bike rated?
For light trail e-bikes with the right spokes, yes. For heavy e-MTB use WTB makes the HTZ with 20% thicker walls.
Is it tubeless-ready?
Yes. WTB lists the KOM Tough TCS I 40 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.
