thenamesross Posted March 10, 2008 Report Share Posted March 10, 2008 Im getting a lot of shudder from the front under braking at the mo. The discs and pads are in great nick and Ive never used them in anger so I wouldnt have thought they would be warped - any other ideas on what would cause the shudder? If it is the brakes I will go for red stuff pads with std disc probably. Any tips on where to get std discs at a good price? Cheers Link to comment Share on other sites More sharing options...
Botang Posted March 10, 2008 Report Share Posted March 10, 2008 You can normally cure brake shudder by braking harder. You need to get them up to temperature by doing so high speed braking when you know its safe to do so and then repeat a few times. The warping effect is normally caused by holding the brakes on at a roundabout/traffic lights which with auto boxes our cars are prone to. The disc is most likely not warped its just pad material has baked onto the surface. By bringing the brakes up to temperature it is possible to clear it. I personally wouldnt use standard discs but use the EBC standard style disc (not grooved/drilled) as in my experience they have been very good. In which case there are many EBC suppliers online so just hunt for the best prices Link to comment Share on other sites More sharing options...
Duffy3074 Posted March 10, 2008 Report Share Posted March 10, 2008 I have to disagree over the cure for shudder, once a set of dics are warped you've two choices, either get them trued on the car (It's essentially a tool that spins them up on the hub and skims them, had it done a couple of times but never on my S8) or get new discs. Once their warped, their warped, albeit Botangs spot on about heat soak causing the disc to warp due to pad contact when their hot. Link to comment Share on other sites More sharing options...
Botang Posted March 10, 2008 Report Share Posted March 10, 2008 [ QUOTE ] I have to disagree over the cure for shudder, once a set of dics are warped you've two choices, either get them trued on the car (It's essentially a tool that spins them up on the hub and skims them, had it done a couple of times but never on my S8) or get new discs. Once their warped, their warped, albeit Botangs spot on about heat soak causing the disc to warp due to pad contact when their hot. [/ QUOTE ] You seem to have misunderstood me slightly duffy. The disc doesnt change shape because of the heat soak, it is just that pad material transfers onto the surface and therefore you can get the discs back to their original condition with heavy use as the pad material clears. I have successfully used this process a few times with no ill effects. Whilst your solution would work I believe its not neccesary. Link to comment Share on other sites More sharing options...
thenamesross Posted March 10, 2008 Author Report Share Posted March 10, 2008 Sounds logical Botang. It would make more sense if that were the case because Im pretty sure theyve never been used hard enough to warp them through excessive heat. Will def give that a try. I like cheap fixes! Thanks for the tip on the discs too (although hopefully I dont need the just yet). Link to comment Share on other sites More sharing options...
shark_90 Posted March 10, 2008 Report Share Posted March 10, 2008 I've always been told that discs don't warp at all. It's just that the surface isn't true due to the build up of pad residue etc on the disc. Link to comment Share on other sites More sharing options...
LostKiwi Posted March 10, 2008 Report Share Posted March 10, 2008 Personally I would never ever go for EBC 'spotties' - the grooved/blind drilled discs. Tried them on two cars and had no end of problems with brake judder after only short distances. The othe problem you can get with heat soak from the pad is that they can heat a local area of the disc to the point where the metal changes composition slightly forming a crystalline substance referred to as cementite. This has different friction characteristics to the rest of the disc hence causes judder. The bad news is there is no way to get rid of it as turning the disc will only remove the upper surface but it permeates right into the disc itself. When looking for replacement discs try www.motorsportworld.com - I've always found them to be very good. I have my eye on a nice set of Tarox grooved discs they stock.... Link to comment Share on other sites More sharing options...
Joylove Posted March 10, 2008 Report Share Posted March 10, 2008 It could also be brake binding. Does it only happen after a long run? Link to comment Share on other sites More sharing options...
Atomic Posted March 10, 2008 Report Share Posted March 10, 2008 [ QUOTE ] It could also be brake binding. Does it only happen after a long run? [/ QUOTE ] I would have thought the opposite. Giving a car a good long run is more likely to free up any moving parts and prevent binding whereas a car hardly used is more likely to have parts partially seize. Only exception I would make to this is that cars can gather a residue on the discs... dust and alike which can bind due to the heat of the discs. I had that in France a couple of years ago with my A8. In the end I just gave the car a good workout and it cured itself. Link to comment Share on other sites More sharing options...
Joylove Posted March 10, 2008 Report Share Posted March 10, 2008 But if the caliper is not fully recoiling the pad might get hot after a run, and deposit onto the disc? Link to comment Share on other sites More sharing options...
Duffy3074 Posted March 10, 2008 Report Share Posted March 10, 2008 I've heard a theory about pad material building up but that was a long time ago when pads were made of very different materials and then the problem was only with competition type material (DS11's etc) with a very narrow, but high working range (Modern pads are a lot better in this repesct). However I've read and seen lots of warped discs, often caused by heat transfer (Pad contact transfers heat into the part of the disc it touches whilst the rest of the disc cools and contracts, next use of the brakes touches the hot part of the disc first as it hasn't contracted/cooled causing it to be heated/expanded again and it's downhill from there) If your solution works I'd be delighted, but also more than a bit surprised :-) Link to comment Share on other sites More sharing options...
PsYcHe Posted March 10, 2008 Report Share Posted March 10, 2008 Looking at my discs when I did the pads last time, they showed evidence of the pad deposits (cementite stuff), though I didn't really feel they were warped as such, but then again, I'm well overdue a fluid change, as evidenced by the scary braking trying to keep up with an S8 over a 10 mile stretch Link to comment Share on other sites More sharing options...
thenamesross Posted March 11, 2008 Author Report Share Posted March 11, 2008 All interesting stuff. Gave the brakes a good work out on the way home yesterday and it has certainly reduced the shuddering. Will give it some more stick in the back roads and see if I can get rid of it altogether. Even if it doesnt completely cure it, it does confirm that there must be some sort of build up on the pads. To answer another question too, its definately not anything to do with the piston sticking etc. I had the brakes apart last month to check them out and all is in good working order. Cheers - will let you know how it goes Link to comment Share on other sites More sharing options...
Botang Posted March 11, 2008 Report Share Posted March 11, 2008 [ QUOTE ] All interesting stuff. Gave the brakes a good work out on the way home yesterday and it has certainly reduced the shuddering. Will give it some more stick in the back roads and see if I can get rid of it altogether. Even if it doesnt completely cure it, it does confirm that there must be some sort of build up on the pads. To answer another question too, its definately not anything to do with the piston sticking etc. I had the brakes apart last month to check them out and all is in good working order. Cheers - will let you know how it goes [/ QUOTE ] They should get gradually better, if you can get them good enough to live with straight away then see how they go it could well save you a new set of discs Link to comment Share on other sites More sharing options...
nikw Posted March 12, 2008 Report Share Posted March 12, 2008 To prevent it happening again in future the trick is to avoid holding the car absolutely stationary on the brakes after a stop as Botang says. My car juddered under braking when I first bought it. I started letting it creep just a little when stopped for lights/junctions/queues or shifting into neutral and coming off the brakes. I've not had the problem since. Link to comment Share on other sites More sharing options...
Duffy3074 Posted March 12, 2008 Report Share Posted March 12, 2008 :-) Good(But surprising)result! Link to comment Share on other sites More sharing options...
thenamesross Posted March 12, 2008 Author Report Share Posted March 12, 2008 None more surprised (or relieved!) than me. Having more fun in it now too. Its easy to slip into old man mode when you just pootle around in D. Using tip most of the time now and giving some stick on the plentiful back roads we have up here. Its continuing to get better so I reckon I'll use the money instead to get a suitably louder rear silencer. Har har. oh, they dont squeak like they used to either so chuffed all round. Cheers Link to comment Share on other sites More sharing options...
Botang Posted March 13, 2008 Report Share Posted March 13, 2008 [ QUOTE ] Its continuing to get better so I reckon I'll use the money instead to get a suitably louder rear silencer. Har har. [/ QUOTE ] And buy Botang a drink Link to comment Share on other sites More sharing options...
Botang Posted March 13, 2008 Report Share Posted March 13, 2008 [ QUOTE ] oh, they dont squeak like they used to either [/ QUOTE ] That'll be because under light use you end up polishing the pad surface, drive it like you stole it Link to comment Share on other sites More sharing options...
thenamesross Posted March 13, 2008 Author Report Share Posted March 13, 2008 Yep, if I make to a meet at any point Im def owe you a drink or 2. Having lots of fun now with the unsuspecting boy racers round here now. S8's are a bit thin on the ground here so no one knows what it is. Means you can have great fun surprising them. Link to comment Share on other sites More sharing options...
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