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The number one cause of car disk brakes warping is by heat. It's not the heat itself that warps rotors. Bike disks are very similar to cars in how they deal with thermal expansions.
It's the cooling down from a long hot descent that warps rotors. You can prevent this by not locking up your brakes after they've become hot. Most people will warp their brakes while waiting to get back on the ski lift or while taking a mid trail 10 min break.
Imagine that the whole rotor is red hot from a 4000 vert ft run down the mountain and you sit there waiting in line for the lift. The whole rotor is going to cool down very quick except for the area where the caliper is still in contact. The caliper itself should also be very hot and will retain heat longer than the rest of the rotor.
By sitting on one spot after riding really hard you are forcing the rotor to cool off unevenly. 90% of the rotor will have lost 50% of it's heat while the portion still covered by the caliper has only lost 10% of it's heat. The portion left inside the caliper (only takes several seconds) will remain more thermally expanded than the remaining 90% that has cooled off and contracted it's thermal expansion. It's in that exact spot where your warp will show up.
Basically sitting in one spot after a hard run is what causes rotors to warp even if they haven't been touched by anything that can bend them. You want to keep the rotors spinning for a minute or two after a hard ride to prevent them from warping due to thermal inconsistancies.. Try pedaling around the lift for a minute or move your bike back and forth to spin the wheels while waiting in line.
Remember this works for cars too. Never brake hard at a stop and hold the brake. Always brake before the stop and coast slowly to a stop. Your front car brakes will last much longer.
It's the cooling down from a long hot descent that warps rotors. You can prevent this by not locking up your brakes after they've become hot. Most people will warp their brakes while waiting to get back on the ski lift or while taking a mid trail 10 min break.
Imagine that the whole rotor is red hot from a 4000 vert ft run down the mountain and you sit there waiting in line for the lift. The whole rotor is going to cool down very quick except for the area where the caliper is still in contact. The caliper itself should also be very hot and will retain heat longer than the rest of the rotor.
By sitting on one spot after riding really hard you are forcing the rotor to cool off unevenly. 90% of the rotor will have lost 50% of it's heat while the portion still covered by the caliper has only lost 10% of it's heat. The portion left inside the caliper (only takes several seconds) will remain more thermally expanded than the remaining 90% that has cooled off and contracted it's thermal expansion. It's in that exact spot where your warp will show up.
Basically sitting in one spot after a hard run is what causes rotors to warp even if they haven't been touched by anything that can bend them. You want to keep the rotors spinning for a minute or two after a hard ride to prevent them from warping due to thermal inconsistancies.. Try pedaling around the lift for a minute or move your bike back and forth to spin the wheels while waiting in line.
Remember this works for cars too. Never brake hard at a stop and hold the brake. Always brake before the stop and coast slowly to a stop. Your front car brakes will last much longer.
