XC riders: Carbon fibre rims?

I'm not scared of a CF frame, but less confident about rims…

Bontrager prototypes:

dumbest thing ever….your rims take so much abuse….i would think with those instead of going out of true they would just snap

whats a set of those gotta be worth.. wow

dumbest thing ever….your rims take so much abuse….i would think with those instead of going out of true they would just snap

ever try sitting on an un-laced rim? it'll bend like butter.

i think they are beauiful… nice race wheels.

ehhh, CF rims work great for road. A friend of mine has his CF roadrims on his cyclocross bike and they are going strong…they take quite the abuse (as most cyclocross parts do) and show no signs of fatigue/failure (he takes them to work with im regularly to do analysis under a microscope for testing reasons).

People dont give composites the credit they are due…

For XC, I'd ride those in a heartbeat.

It'll be a while yet before carbon rims work for street riding but for current XC courses they should work a charm.

dumbest thing ever….your rims take so much abuse….i would think with those instead of going out of true they would just snap

well, if the 15 year old carbon fiber expert says it, thatn it must be true :rolleyes:

They look sick to me. For the mild XC course, i would use those with no hesitation. Though I would be very hesitant about riding them on anything other than smooth dirt. Im not saying its not possible for those to be able to take some abuse (in fact i bet they can handle more than it would seem), its just i dont wanna be the one to find out what the thresh hold is on those suckers hahaha!

Youwza. I'd hit that. CF has proven to be strong before and will continue to.

Tho, I'll admit, I'd be a bit scared of shattering them/snapping them… I mean, how strong can they be? As good as normal rims? probally… who knows…lol

They look sick to me. For the mild XC course, i would use those with no hesitation. Though I would be very hesitant about riding them on anything other than smooth dirt.

I'd use them… if they were somehow discounted, free, or given as a sponsorship. Not sure I'd pay full price for them. I'm less scared to ride light stuff now, weighing 165, than I was when I was 195-200 pounds.

I wonder how much weight you save per rim over aluminum disc-specific rims? I know light XC weight aluminum rims (Mavic, Sun) are around 440-450 grams each. My guess is the Bontragers come in at 370g per rim.

those are soooo nice and would look so cool on my xc bike just because they are carbon

dumbest thing ever….your rims take so much abuse….i would think with those instead of going out of true they would just snap

Roadies have been running them for years.

My worry is, who wants to deal with gluing mountain bike tires on? I know Thomas Frish…whatever….was running some 650 carbons with tubular tires for STXC. They held up well.

The new carbon stuff is starting to be pretty tough, enough that it can handle XC loads fairly easily. Bontrager also has the trek engineer forces behind it so I guarantee that if they do produce it that it will be up to par. Though the hubs may be a different story.

Also carbon rims do not go out of true. They crack. So if you can make them strong enough to avoid cracking then you have a sick ass uber light wheel with incredible ride quality from the tubulars. /xc geek

The Ito

EDIT:
Wheel guru Keith Bontrager is known to be a huge fan of carbon fiber as a rim material for road bikes, so these pics of proto mountain bike wheels with carbon rims aren't entirely surprising. But for anyone looking to lose some weight off a racing mountain bike, they're still pretty exciting!

The rim
Details are currently sparse, but according to Gary Fisher team mechanic Ben Coates, they're significantly lighter than Bontrager's current aluminium-rimmed wheels (and Bontrager's Race X Lite MTB wheels are already some of the lightest available); and they're stiffer. The spokes used in these wheels are thicker than usual for Bontrager's lightest wheels, Coates said, and the wheels still end up lighter. Bring on the version with 14/17 spokes!

Side view shows the rim shape
Close examination of the pics points up a few other details. These will be disc-only rims, which makes perfect sense for carbon rims on mountain bikes, given the marginal braking of carbon wheels on road bikes - with no braking surface nobody will be tempted to build these rims into wheels for a rim-braked bike. The hubs appear to be DT Swiss units (probably 240s) with Center Lock spline, like the current Race X Lite. These wheels are using DT's adapater that mounts a six-hole rotor on a Center Lock hub, however.

There's no word as to whether these wheels will work with UST tubeless tyres or Bontrager's 'Tubeless ready' sealant system, but given Keith Bontrager's liking for tubeless tyres, we'd be surprised if they're not.

And from the third photo I saw it appears to be a clincher!

Carbon fibre FOG

Well they do look cool. My concern is that the inevitable scratches rims get would weaken them. Maybe not a big deal for most XC but I find my rims get scratched up over time from rocks and stuff. I guess they could have a thick clear coat on them but I'd bet it isn't too thick as that would add weight.