Brake disc warranty

Joe_Horner

Strider590 wrote: »

https://www.google.co.uk/#q=brake+disc+warp+myth&spf=68

The thing is, while I agree to a point, the first link on that search includes a fairly large caveat which I briefly alluded to in my last post:

With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing [...] I have never seen a warped brake disc.

That's a fairly big "presuming" even with many garages, let alone backyard mechanics!

debtdebt

Yep you're right. Just taking this slightly off topic but when replacing the disc, obviously after cleaning the crud off with a wire brush and airline, would you put some copper grease on the hub to avoid a disc welding itself onto the hub or would that interfere with the mating surfaces?

Joe_Horner

Disks should be fitted with the mating flange clean and dry, as should wheels.

The wheels, disks and hubs rely on friction to stop them rotating relative to each other and any grease reduces that friction. The wheel bolts aren't designed to act in shear which is what you get if you reduce the friction between the mating faces too much.

A little copper grease on the locating hole of a wheel is fine but the flat surfaces should be meta to metal.

System

Strider590 wrote: »

Warped brake discs/rotors is a myth,

Riiight.

https://www.youtube.com/watch?v=AGIP7bH8QV4

Strider590

Tarambor wrote: »

Riiight.

https://www.youtube.com/watch?v=AGIP7bH8QV4

That's run out, not warping.......

takman

To warp your discs you would have to be acclerating and braking like you were on a racetrack and then when they get hot enough (which would also have a very noticible smell) you would need to stop the car and hold the brakes on hard for an extended period. If your lucky you may then be able to warp your discs.




There is no chance that the discs are warped.

thescouselander

I agree warped discs are a myth. Discs are very strong - you could hang the entire cars weight off them and they wouldn't bend. As above the problem will be brake pad deposits on the disc surface as a result of driving style.

I usually find when a car has juddering brakes a few rapid stops from high speed is enough to clean the discs up.

Joe_Horner

takman wrote: »

To warp your discs you would have to be acclerating and braking like you were on a racetrack and then when they get hot enough (which would also have a very noticible smell) you would need to stop the car and hold the brakes on hard for an extended period. If your lucky you may then be able to warp your discs.




There is no chance that the discs are warped.

That's true only with the provisos in the bit I quoted pabove. Poorly fitted disks can and do warp because of uneven stresses
in the metal.

Part of my job involves bending steel parts at blue temper without breaking them. You work the two sides unevenly and the surface stresses created cause the metal to curl to one side. It doesn't take much force (or you'll break it - blue steel isn't very good at bending) just a lot of repetitive burnishing or light hammering.

That's exactly what happens with a disk that's mounted with too much runout - the pads alternately work one side then the other on every revolution of the wheel and, over enough repetitions (typically around 10 per second @ 60mph), the metal bends even under relatively light force.

forgotmyname

So because they say they have not experienced a warped disc and created a page with various myths that i have never heard of they are right and i am wrong when i HAVE experienced a warped disc?

MYTH 2, Racing discs are steel? Never heard anyone say that.
MYTH 3, A soft pedal is brake fade. Not heard that either.
MYTH 4, never heard anyone say that. You would need someone that
knows nothing about cars.

System

takman wrote: »

To warp your discs you would have to be acclerating and braking like you were on a racetrack and then when they get hot enough (which would also have a very noticible smell) you would need to stop the car and hold the brakes on hard for an extended period. If your lucky you may then be able to warp your discs.

Or you could have a seized caliper piston or sliders. If you heat the hell out of one side of a vented disc and not the other due to a piston being seized then you can warp a disc.

I went down a 1 in 6 hill a few weeks ago and had to brake hard at the bottom. A few miles later I stopped at some roadworks and there was smoke coming up from the nearside front due to the caliper seizing through lack of use over winter. Cue new pads, disc (because it was warped) and caliper.

I've had warped discs several times over the three decades I've been driving. I've also experienced warped drums on the trucks I've driven too.