Cheeto

I was curious today, and after a hard, but short stop in my drive way I felt the rotor... burnt the tip of my finger lol. just thought I'd start some useless conversation. I didn't think they'd heat up that quick/hot.
I can only imagine how hot they get on a Downhill race or something.

ca7erham

My front rotor got warped from the heat of a decent on a trip in Colorado and I burnt/cut a piece of skin off of my shin the other day (after one of our beastly Ohio hills). Looks like a cut from a razor. Next time try your car's front rotor. . .

Cheeto

lol, I washed my car after i was hot rodding in it, I sprayed the front rim with the hose and an explosion of steam happened!

thats some serious heat to warp them though.
does this heat have any effect on pads?

scrublover

You could possibly screw up your pads if you get things too hot, and rotors, but it's generally a non-issue. Yes, they get hot. Larger rotors help, as well as vented calipers and so on, but they'll still easily get hot enough to steam and burn. Doesn't really take much.

Now don't go sticking your tongue in the light socket, mkay?

ca7erham

After a 3 mile decent with long straights and sharp hairpins there was an odd burning smell coming from the pads and I had almost no stopping power. After about 15 mins or so it got a bit better. But then again the pads were already slightly ruined anyways, so I didnt notice much. But the rotor must have been glazed over because I had much more stopping power after I replaced it. Also, you will warp your rotor if you water it. . . (but I think you already know that so. . .)

Cheeto

Ill keep that in mind when the rain comes this winter, the creek at Thomson Trail will be flowing. its at the bottom of a fairly agressive down hill..

wmodavis

Brakes work by converting the kinetic energy of your forward motion into heat at the pad/rim or pad/rotor interface. A big function of the rotor/rim in braking is to dissipate the heat generated. In other words they act as a heat sink to remove heat from pads and transfer to the rim/rotor then to the air. Obviously too much heat can damage anything even your finger. The rim/rotor need time to cool. Give them a break once in a while by hitting a tree to stop.

eminefes

And if you're riding on the road, give them a break by hitting a car to stop.

sirtigersalot

i've heard of brake systems getting so hot that the fluid overheats and causes the brakes to get stuck on, I know in cars you can get fluid fade by boiling the brake fluid (usually only happens to racers who repededly brake hard from like 100+) but on cars you have that big fluid resevoir so instead of brakes getting stuck on you get lots of gas in the lines that makes the brakes suck big time and then you crash lol, thats why they buy expensive brake fluid. Never thought of warping bike rotors, cause u can just bend em back and resurface with super fine sand paper but w/e, also i don't think bike rotors get hot enough/ are too small to warp from getting a little wet, car rotors do get that hot and ar thick enough that the differences in heat and the rapid cooling causes warping if you hose down hot rotors

oh and on a random note it would be cool if someone made a double brake for downhill like on yamaha motorcycles, they have a rotor on each side of the wheel and of course each rotor has its own caliper. The other day i saw one that had 6 piston calipers on each side and huge f-ing rotors, now thats some stopping power, just imagine running 2 codes on dual 8in rotors, lol i'd go over the handlebars, also i'd bust my fork cause i don't have a dh bike

also don't touch your rotors even when cold cause the oils in your fingers are bad for the brake pads , if you do touch your rotors or get oil/grease on em clean them with rubbing alcohol and paper towels (not cloth shop rags cause the fibers get stuck in the pads, paper just burns out cause its crappier)

BMX Race Bikes

Yes!
These rotors really heat up !!

roccobike

Been there, done that. Yeah, burned the finger too, (lol). Felt pretty stupid. After working on so many auto brakes you'd think I would know better.

Cyclist30907654

Bike brake fluid boils too.

And the double brake thing has been done, and found to be unnecessary.

scrublover

Larger rotors, a good bleed, and good pads for your system. If your system can take anything fluid-wise that can handle higher heat, swap fluids when doing a bleed. (ie: Avid hydros taking DOT5.1 vs. the stock fluid.

Also, don't ride your brakes.

Quick_Torch C5

I'd try not to wash your car after "hod rodding" it, iron doesn't take too well to sudden extreme temperature changes.

ps-what car are you "hot rodding"?

scrublover

The sweeeeet ride.

solbrothers

it makes perfect sense. just as in a car, the disc brake will generate heat.

sirtigersalot

yeah thats what i was getting at when i said i'd heard of the heat causing the brakes to lock up, its never happened to me so my info is second hand but it was my understanding that in a bike unlike a car when the fluid boils the resevoir isn't big enough to account for the added pressure, so its basically like squeezing the brakes, the pads rub or in some cases lock up the brakes until they cool down. in cars however the bigger openbath resevoir allows for pressure to be releaved, then you press the pedal and of course the gas is compressable so the pedal goes to the floor without putting much pressure on the pads, and you fly off the track

wow i didn't realize anyone did the double brake thing, cause you would need brake tabs on both sides of teh rotors, and yeah it would be way overkill but really funny

wheelhot

avoid holding your brake for too long, cause it will heat up your rotor which could result into your pad not to be able to get a proper grip to the rotor.

Instead feather the brakes (Im not sure if I spelled it right), what I meant is, you push release push release your brake lever, that should prevent your rotor from getting too heat up.

Chris_F

On cars a lot of "warp" isn't really warp, it's pad material deposited on the rotor surface. This happens when the rotors and pads get very hot and the car comes to a complete stop and remains motionless with the brake on, leaving the pad in contact with the rotor. An example may be coming to a fast stop off of the interstate and remaining stationary at a stop light with the brakes on. I think this is more often responsible for car rotor warp than actual warp.

Something to think about on the bike: if your brakes are hot then don't leave them on after you've come to a stop, just put your foot down and let go of the brake (not possible in a car obviously).

Quick_Torch C5

This 100% incorrect. I'm an auto technician by trade, and never had a warped rotor due to "deposited pad material". In fact, I've never had to scrape or turn any pad material off any warped rotor. The "pad material" turns to dust around the brake/wheel assembly but is not thick or solid enough to cause any runout(warp). I won't go too deep into this but simply put, rotors pulsate due to excessive lateral runout or variable parallelism from excessive heat, uneven side-to-side pad wear, or incorrect/uneven torque of the lugnuts.

Chris_F

https://www.stoptech.com/whitepapers/...otors_myth.htm

Quick_Torch C5

You can quote any article you read but keep in mind it is from an (biased)aftermarket brake manufacturer who specializes in selling their rotors, not an Original Equipment Manufacturer. I can agree that a very hot brake pad transferring heat onto a rotor may cause hot spotting and runout, but none of the 3 OEM brake classes I have attended or the 15 years of on hand brake experience has lead me to believe that the pad material itself deposited on the rotor will cause the pulsation. I've even wiped off brake dust off of hot rotors before and they are nowhere as hot as the rotor as the dust particles are so small the heat is quickly transferred.
If you were trying to say the pad is transferring heat to the rotor and causing hot spots, then I can agree with that. Just be careful about writing about something you just read without experience.

gmcttr

But that's what the internet is all about! I learned a long time ago to fact check for myself.

junkyard

Cheeto cheeto'd his finger.

EthanYQX

Don't do that. Do you know what shock cooling is?