Front and rear discs on my SS are warped so that they rub against the pads on either side. How has this happened and how do I stop it happening again?

It’s Karma for riding a SS!

Heat I’d imagine. Stop braking as much?

“Don’t brake! Don’t brake!” is WCA’s catchphrase I’ll have yoo no.

solution: don’t drag your brakes, brake sharply into the corner, then let go again.

problem: braking surface heats up and expands, so the circumfance of the circle gets longer, but is still contained by a smaller spider, as a result the exra length goes somewhere and the rotor warps.

too much braking! 😀 (get some bigger/floating rotors)

you sure the wheels are properly seated in the dropouts and the QR’s/nuts done up nice and tight?

Make sure after downhills that you don’t hold the brakes on when you stop as well. This allows the rest to cool but the hot pads, fluid etc leave one area still hot which can lead to deformation.

You need to get them ‘effin hot to warp them. I’ve not had that problem with rotors hot enough to go purple. You probably knock them or shove the wheel in poorly so they bend when slotting the rotors into the caliper. Just use a spanner to straighten them.

Discs warp because because of the following; When most discs are made they start life on a big roll of steel, this is then laid flat and then it goes to a bit of kit with a lazer cutter that cuts the disc out of the steel, this is super high temperature and causes a slight bit of memory (warping) in the metal. When it cools down the rota is flat and true, when the rota gets hot when you use the brake the rota wants to bend into the shape when the rota was cut. Why? don’t ask me… This is one of the reasons some brakes squeal when they get hot.

The best type of rotas are ones that press cut (a big heavy cutter that stamps out the rota). Companies like Galfa make these rotas.

I’d say that in the great scheme of things bike rotors are punched/cut out of a sheet of cheapish metal don’t get left to “age” and then the heat in / heat out relieves these stresses by warping the disc. Like only using a used enging block to build a tuned engine. I’m sure many will disagree though

anyone else heard the story about old BMW F1 engines (in the turbo days) being left oustide the factory for workers to piss on?

It will indeed be partly down to cheap production methods (they should be heat treated while pressed flat to ensure no residual stress, as Hope do IIRC). That said its FAR more likely you just twanged them with a rock etc, I’ve had my rotors blue in the alps and didn’t get any warpage. That said, they were Hope and they had a stuck piston.

thisisnotaspoon – cant see that being true, a) Leaving them to age without heat wont do much and b) Pee may damage the metals and c) I cant see the workers wanting to pee outside when they could have a toilet.

I always thought it was due to irregulaties in the metal becoming apparent when they got hot? Im no engineer though. It happens more to the cheaper discs too.

BMW F1 engineers of the Mid-eighties turbo nutter phase used to use 4 cylinder blocks from high mileage 3 series BMW’s as the Cast had been heat cured over many thousands of miles and cooled again, all done gently at road speeds / stress, this would take too long to replicate in an engine shop.

Also when it comes to building the high power Nissan Skylines so fabled in the East and becoming ever more popular in europe, the block of choice was a well aged R32 (first gen of the twin turbo RB26 DET nutter engine) as it would cope with the stresses much better, akin to the BMW engines of the turbonutterbastard era.

On the problem of your brakes, fit bigger discs 😀

i’ve read it suggested that even car discs do not warp, that the apparent change in thickness is the result of a large deposit of pad material at the measured point, and this would explain why sometimes you can ‘get them back’ by getting them ba5tard hot again. i don’t have the necessary metalurgical quals to argue the toss though, so i’m not going to.
on bikes? you bent it.

They are so easy to bend on bikes – I think it’s in the car or the garage when they get hit or pressed. I don’t think they warp due to heat, but I dunno.

I am guessing that I must have bent them in a crash at some point as I can’t imagine braking hard enough to really heat them up.

Any idea why they put the pads so close to the discs? Surely they could leave more clearance and use move fluid movement to keep them feeling sharp.

I agree with solamanda – we have had the discs on the tandem hot enough to go blue and the pads were smoking. No warping. I think it will be down to a knock

Then they’d get heavier tho… you’d need bigger everything.
Bigger master cylinders (to use more fluid) would give you less power but more movement.

according to the STW disc brake review the new shimano XT and SLX’s servowave thingy puts the pads further out from the rotor so they don’t drag.