Jigging AP Brake Discs

[lvjost]

Went on a 700km Tour from Germany to France into the "vogesen" (a middle height beautiful mountain chain). First 200km of German autobahn with (a legal) 150mph...then into the mountains and 350km on small and very low traffic country highways/lanes with a lot of turns and serpentines meaning going full throttle in 2nd, 3rd and 4th Gear and really braking a lot and intensely...After approx 1 hour the brakes seemed to be very hot...Since I have a jigging/pulsing felling, when I step on the brake pedal....A local specialist said, he thinks of the mountain trip causing the AP Discs to get very hot and then slightly deform so the now have a little unbalance to the sides.... Anyone experienced something similar ? What to do, replace the brake disc after every racy ride ?

[m3desmo]

Does sound like a disc/discs may be warped. Mountain driving, especially downhill sections, puts more continuous heat into the discs and they don't get a chance to cool down much, even more so than spirited normal driving conditions.

[v8owner]

Does sound like they are warped?...
get them skimmed, if theyve been that hot/cold now they shouldnt warp to any extent again.

[m3desmo]

The brake overheating / warping may have been caused or at least made worse by the fact that you have used the front clip vents to duct air into the cabin and not into the front wheel well as was probably intended. Perhaps it would be better to use the front clip vents for ducting cooling air to the brakes????? Just a thought.

[Hugger Z]

It is possible that they are warped. How bad is the shaking? Can you feel it in the pedal? There are a bunch of reasons that cause brake pulsation. One is warped rotors which can be checked with a runnout gage (dial indicator). It is also possible that with the heat your brake pad material left some residue on the rotors. This deposited material can cause pulsation. I would suggest you drive the car some more and see if the pulsation persists or eventually goes away as the pads clean the rotor surface again. Or you can have your rotors bench ground (since you can't turn a cross drilled rotor). And see if that helps.

[GreenV8S]

Localised overheating on discs can cause them for form a crystaline structure which is slightly harder wearing than the iron around them, and can lead to a high point on the discs. This gets hotter which makes the problem spread. The solution is to skim the discs, although you may be able to cure it by some vigorous sanding with garnet paper.

[menostig]

The instructions for my AP Racing brakes explain how to blue / bed them in for track work so as to avoid this kind of problem. Sorry, bit late now.

cheers
Roger