Sea Otter: Kappius launches KR-29-XCW wide MTB rim

New rim's 41mm internal width increases tire volume — and traction

Sea Otter Classic Wheels

2015 Sea Otter Classic

If you're in the wider-is-better camp, the choice is clear here.

If you’re in the wider-is-better camp, the choice is clear here (click to enlarge).

Colorado’s Kappius Components made a compelling case for its new KR-29-XCW wide MTB rim at the Sea Otter Classic. In a side-by-side comparison, the new Kappius rim netted nearly a third of an inch greater tire width than an ENVE XC rim when both were mounted up with 2.35 Maxxis Ikons.

The benefit of wide MTB rims is also pretty compelling: improved cornering and braking traction, reduced risk of tubeless burping, and the ability to run lower pressure. That final point is critical. Wider rims help separate tire pressure from sidewall support, so you can run lower pressure and not risk an unnerving wallowing ride feel.

The new rim retails for $699 and has a claimed weight of 450g.

The new rim retails for $699 and has a claimed weight of 450g (click to enlarge).

As the photos below illustrate, the Kappius rim pushed the tire to nearly 2.45 inches, while the ENVE maxed out at 2.18. Both tires were pumped to 15psi. And Kappius co-founder Rus Kappius claimed he’d raced the KR-29-XCW earlier that day at 12psi.

“Traction was amazing,” he said.

The 2.35 tires ended up at almost 2.45 on the Kappius rim.

The 2.35 tires ended up at almost 2.45 on the Kappius rim (click to enlarge).

Indeed, following the likes of Ibis, Kappius has pushed into the wide rim arena with a new hoop that measures a claimed 46mm outer width and 41mm internal. For compassion sake, the pictured ENVE is 24mm/19mm. This added width nets increased tire air volume, which means greater bite and stability, especially when cornering. At 15psi you could easily fold the bead of the Maxxis tire mounted on the ENVE just with your hands, while the Kappius held firm under the same duress.

On an ENVE XC rim, 2.35 became 2.18 at 15psi.

On an ENVE XC rim, 2.35 became 2.18 at 15psi (click to enlarge).

The new rims have a claimed weight of 450g and retail for $699 apiece. A fully built wheelset using Kappius KH-1.5 hubs sells for $2200 with a claimed weight of 1550g. The wheels are tubeless ready and have an offset spoke bed that’s designed to increase strength. Here’s a full rundown of spec and highlights of the new Kappius KR-29-XCW rim.

  • 46mm external width
  • 40mm internal width at bead
  • Recessed bead channel to prevent burping
  • Shallow, wide center channel for ease of tubeless inflation
  • 5mm offset spoke bed for added wheel strength
  • 450g per rim (28- and 32-hole)
  • $699 per rim

For more information visit

This article is part of Mtbr’s coverage of the 2015 Sea Otter Classic in Monterey, California. For more from Sea Otter CLICK HERE.

About the author: Jason Sumner

An avid cyclist, Jason Sumner has been writing about two-wheeled pursuits of all kinds since 1999. He’s covered the Olympics, Tour de France, MTB world champs, and dozens of other international cycling events. He also likes to throw himself into the fray, penning first-person accounts of cycling adventures all over the globe. Sumner has also done extensive gear testing and is the author of the cycling guide book "75 Classic Rides: Colorado." When not writing or riding, the native Coloradoan can be found enjoying life with his wife Lisa and kids Cora and Tommy in and around their home in the MTB Mecca of Crested Butte.

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  • Gator says:

    That’s really light for a rim that wide, Kappius is always thinking out of the box, but they still have the hook in their design.

  • Ehhh D? says:

    What’s the best aggressive, lightish front tire for wide rims? Tires designed for narrower rims tend to get squared, and when you lay it over the side nobs just aren’t there. Are tire manufacturers making tires designed for these wide rims yet?

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