carbon wheels on a hardtail

i'm thinking of building a set of carbon rimmed wheels up for my hardtail

for the last year i've been running a set of wtb i25's - they've been great, and hassle free, but i often feel like i'm lugging more weight around that necessary for much of the riding i do

the year before that, i was running a set of pacenti tl28's - noticeably zippier, but they dented so easily i felt like i was holding back on them, and they required more maintenance than i liked

i've been thinking that a set of carbon rims would provide for a strong and light set of wheels. but i've also heard that carbon rims are noticeably less vertically compliant than comparable aluminum hoops

thoughts, theories, experiences to share?

i'm thinking of building a set of carbon rimmed wheels up for my hardtail

for the last year i've been running a set of wtb i25's - they've been great, and hassle free, but i often feel like i'm lugging more weight around that necessary for much of the riding i do

the year before that, i was running a set of pacenti tl28's - noticeably zippier, but they dented so easily i felt like i was holding back on them, and they required more maintenance than i liked

i've been thinking that a set of carbon rims would provide for a strong and light set of wheels. but i've also heard that carbon rims are noticeably less vertically compliant than comparable aluminum hoops

thoughts, theories, experiences to share?

Im going to guess you wont notice the ~200g you would save (~100g / wheel) in terms of weight. As far as stiffness goes, carbon hoops are MUCH stiffer than Al. Not sure this is something you would want on a hardtail? The vertical 'give' of the rims probably helps somewhat with making the ride a bit more compliant.

I'm not sure how you ride, but it might not be the best combo for a rear wheel unless you plan on running a lot of pressure. Front would be ok though.

Im going to guess you wont notice the ~200g you would save (~100g / wheel) in terms of weight.

you'd guess wrong. perhaps i'm extraordinarily sensitive, but i've definitely noticed that amount of weight difference in previous back-to-back comparisons

As far as stiffness goes, carbon hoops are MUCH stiffer than Al.

this is what i'm concerned about

I'm not sure how you ride, but it might not be the best combo for a rear wheel unless you plan on running a lot of pressure.

rear carbon rim on a hardtail you mean. i'm not a terribly aggressive rider

why would high pressure help - less chance to dinging the rim on landings/impacts?

Yeah, it's important to check your pressures with carbon. Higher pressure means it harder to compress the tire and thus harder for the rim to make contact with pointy rocks.

I've got a buddy who smashed 2 rear rims fairly completely on his hardtail. But hes quite aggressive.

Having some rear wheel travel helps a lot with all of this.

I have them on the below. They ride great. Big tires and lowish pressure. Rear is around 25 PSI. Light Bicycle set.

If you pay attention (and ride at times, or are otherwise in a position, that you see a lot of bikes), it is remarkable how many rigs you see with a carbon front rim and an aluminum rear.

If you ask the owners, it is remarkable how many of those riders HAD carbon rims front [HTML_REMOVED] rear.

Food for thought?

I rock carbons on a couple burly ti HTs. They're awesome for XC and AM pedally stuff.
You don't wan't carbon on the rear for chunky airy brappy stuff, because it won't last long.

I cacked one on the rear. Didn't go out of true, didn't even lose air. Just noticed a crushed sidewall section at the end of the shuttleday when putting the bike away. Pretty sure I know what did it, and we had a couple more runs after that, so it held up. Got it warrantied for the price of shipping.

Will turn the busted one into a table or a couple sweet coat hangers…

- Make sure you go hookless: stronger bead area and more resistance to folding and cracking under sharp hits.
- The 25mm inners / AM 29 / hookless rims, which I have, have been solid and are ~ 445g / rim.
- The next step down in rims would be something like 23mm inner / XC 29 / hookless at 100g less per rim. I wouldn't hesitate to run those either but why get greedy: Flow EX is 520g for a 29 hoop and I'm 75g per rim, 150g per wheelset lighter with a very durable rim.

With carbon hoops, DT revolution spokes don't feel flexy anymore on a 29er. I managed to build up my wheelset at 1645g:
- AM hookless rims
- DT rev spokes
- 240 hubset
- Alloy nips
- Tape
- Brass valves (more weight savings to go with alloy valves! I have some coming. I think the savings are 20g / pair)

Im going to guess you wont notice the ~200g you would save (~100g / wheel) in terms of weight. As far as stiffness goes, carbon hoops are MUCH stiffer than Al. Not sure this is something you would want on a hardtail? The vertical 'give' of the rims probably helps somewhat with making the ride a bit more compliant.

Agree. I got some DH layup Derby rims for my E29. They are very stiff. On my bike they're awesome but on a hardtail they might be too stiff. Maybe a more compliant carbon rim would offer a good compromise? My wheels laced up to 1900g with Hope hubs, which is comparable to the Flow wheels they replaced - but these were built with toughness in mind. Even if you built them up lighter I'm not sure they'd necessarily be more compliant.

100 gm per rim is a big difference that any performance rider will notice. Big help climbing technical trails because you get the quick acceleration you need to get over a steep bit. Heavier wheels and tires change that timing for the worse. Carbon rims are stiffer. Again you feel that accelerating. Very zippy and snappy. But they can feel harsh on bumps out back on a hard tail. Big soft tires mitigate that a great deal though.

With carbon hoops, DT revolution spokes don't feel flexy anymore on a 29er.

good point ken. i usually build with straight gauge spokes, but could use butted spokes to save weight and have a stronger, more forgiving wheel

I have some coming

can't keep a good man down :)

Maybe a more compliant carbon rim would offer a good compromise?

does anyone offer this? my experience with carbon bike parts is relatively limited - road bike fork, mtb bars - but they dampen vibrations and shocks rather than exacerbating them. consensus on rims/wheels is the opposite - why is that? where's my laterally stiff, vertically compliant option!?!

I'm also on the carbon-front alu-rear program after cracking one of my old-skool 26" "Nancy wide" LB carbon rims. I do notice the weight difference (Flow vs LB carbon). If I wasn't such a clumsy hack I would get one of the new hookless LB rims.

I liked the way the carbon rolled but couldn't tell any difference in "vertical compliance" switching from alu to carbon and back again. I run least 2.3" tires for everything though.

For what it's worth, I'm loving the WTB i23 as a lighter alternative to Flows.

I haven't noticed a problem yet on my LB rims. They are the wider 33mm hookless variety. I have scuffed them up a bit. On the HT I have hit some hard rocks, but haven't noticed damage.

I was even using them in the bike park, but on a Blur TRc for a couple del boca vista and smoked a rock with no issues.

I do find the ride a bit bumpy, but with reasonable tire pressure, I think they ride well.