heat resistant carbon clinchers

limoneboy
limoneboy Posts: 480
edited September 2013 in Road buying advice
well, just returned from italy and after a hors cat descent of 6000ft my rear carbon rim melted under braking , i did the usual stuff moving between front and back but this didn't help, they where gigantex rims .

just wondering if anyone has had this issue with other manufactures as i what to replace this wheels but don't what the same issue again , or can recommend a light/stiff set of 38mm rims which would with stand this kind of ride.
last month wilier gt -this month ? bh rc1

Comments

  • Personaly, I wouldn't use carbon rims in the mountains. If you ever do a GF in the alps, the smell of overheating carbon and cork on the descents is worrying.
  • As far as I know, the only manufacturers that have come out with resins that don't delaminate at high temperature are Zipp Firecrest and Mavic with their latest C 40.
    There are no rims available to build with such resins... so if you want to descend the alps safely with carbon clinchers, I suggest you buy these (they ain't cheap though!)

    http://paolocoppo.drupalgardens.com/con ... u-buy-them

    otherwise go for carbon rims with alloy brake track (which are heavy)
    left the forum March 2023
  • neeb
    neeb Posts: 4,470
    These days if I'm going to big mountains I just swap out the front wheel for a low/medium profile alloy clincher. Just not worth having to deal with crosswinds on descents, poor braking, possible overheating etc. At least if the front wheel is alloy you know you can brake as much as you like on it without issues, and crosswinds are only really a problem with the front wheel.
  • Grill
    Grill Posts: 5,610
    Check out Reynolds as they have their propriety CTg brake track. Stays cool even under sustained heavy braking, but I agree with what other have said in that carbon clinchers are just not the best idea. I'd go tubs or alu brake track.
    English Cycles V3 | Cervelo P5 | Cervelo T4 | Trek Domane Koppenberg
  • The other thing to think about is technique. Rather than dragging the brakes, braking should be short and hard as you approach a bend then get off the brakes between corners. This gives the brakes time to cool down.
  • Possibly a silly question but why are tubs better for this? When things overheat is it the actual rim that gets damaged or just the tyre/tube. I can understand why a tub would be better if the damage is to the tyre/tube, but not really why they are better if the damage is to the rim?
  • Grill
    Grill Posts: 5,610
    I've seen alu rims go due to heat as well...
    The biggest advantage to tubs is that they can take much higher pressure. As the heat builds on the rim the tube will expand and on a clincher will pressure the bead against the rim. Not only does this not happen on tubs due to pressure and placement, but if you were to blow out you're less likely to die on tubs. As far as the rim melting, lots of carbon rims have specific treatments on the brake tracks to dissipate heat. Mavic, Reynolds, Zipp, just to name a few won't heat to the extent of an OEM rim like Gigantex.
    English Cycles V3 | Cervelo P5 | Cervelo T4 | Trek Domane Koppenberg
  • gloomyandy wrote:
    Possibly a silly question but why are tubs better for this? When things overheat is it the actual rim that gets damaged or just the tyre/tube. I can understand why a tub would be better if the damage is to the tyre/tube, but not really why they are better if the damage is to the rim?

    In the specific case (delamination rather than tyre explosion) tubs or clincher makes no difference. Also, the treatment to improve the brake track are not the same thing as using a different resin to improve the thermal resistance.
    While Gigantex rims are treated to improve braking, they don't have a high Tg resin. In other words there is no improvement on heat resistance, only on the pads/rim contact to give you a sharper action. Heat dissipation in a material which is essentially a heat capacitor is always going to be problematic... however you can make it so that it resists to the heat better.
    The fibre can withstand a thousand degrees, so that's not the issue, but the thermoset resin does not go over 100-120 degrees, typically. there is a lot of research in high Tg (glass transition) thermosets, as carbon fibre enters more and more sectors of the aerospace market
    left the forum March 2023
  • Thanks ugo/Grill. All very interesting, wheels have changed a lot since the days of trying to get the rust off the ones on my old "Raleigh racer" with a tin of chrome cleaner!
  • gloomyandy wrote:
    Thanks ugo/Grill. All very interesting, wheels have changed a lot since the days of trying to get the rust off the ones on my old "Raleigh racer" with a tin of chrome cleaner!

    But have they really changed?? :roll:
    left the forum March 2023