Brake disc change

I am about to change the front brake discs due to warping vibration felt thru the pedal. My question is : the pads are still new do i have change them too?

Come on, it's an easy question guys! :-P Waz

You don't have to change your pads. It will take a little bit longer to have the pad bed in with the new rotors.

exactly what i thought.. waz

Yes you have to change the pads!!! Trust me... I have been there done that.

I've always been told to change the pads once the rotors were changed.

I change rotors every year because of track driving and have done new rotors old pads and new rotors and new pads. I don't have issues either cases. The pad bed in period seems to be long with old pads. Can you guys tell me the issues with old pads and new rotors?

exactly, is there a clear reason why not?! just to know..

Hi, since the old discs were worn the old pads would have adapted to the surface of the old discs. If you use them with new discs, the old pads will not be in contact with the whole surface of the new discs, and both the new disc and the old pads will wear excessively on the contact points. In effect, you will almost copy the imperfections of the old disc onto the new disc. Cheers, Uwe

I agree. Not to mention until the rotors and pads are in full contact you may experience reduced stopping power and more of chance of heating up things during hard breaking. This is why when replacing pads only cars many shops "turn" the rotors. They essentially take the rotor off and attempt to shave down the rotor to some degree to make the surface smooth with no grooves so that the new pads will have smooth surface. Obviously as a rotor wears the ability to do this lessens because the rotor thickness decreases. The old pharse "scarring" the rotors come from the the fact a portion of the rotor may be deeply marked enough that "turning" will not get it out. Your brakes are too important on this type of car. Replace both. The increase in cost is minimal. This way you know you are starting with good pad and rotors. Just my $.02

I can give you the track perspective on this. You change what is worn out. If you need new pads (which you do frequently) you change just the pads. If you need rotors (generally because of cracking), you change just the rotors. You don't need to change both. Your pad surface will adapt to your rotor surface very quickly. Jim

Jim B coments makes sense if the rotor are cracking. But since the rotor is out of round I would do both. The uneven rotor will make the pads uneven and cause the new rotor to ware a little uneven. The only way is to true the pads to a flat surface to make the old ones work right.

I think i will have to change both since the rotors are in such a bad shape.. I am convinced now! my new quote: too bad for the new pads! Waz

Waz, Here is a good article on the subject. Two key points that I took from this when I read it a couple of years ago. One, your rotors are likely not warped. Two, you are better off changing just pads or rotors. Not both. Sorry it took so long to pass this on. I had to search a bit. One point that it doesn't make. Rotors don't really damage your pads. They may put small groves in them but that's really no big deal. They will wear down in no time and they won't effect your stopping performance. Again, if I were you I would look the pads over. If they are thick and not breaking up, keep them. Just my opinion. You should do what you feel most comfortable with. http://www.stoptech.com/whitepapers/...otors_myth.htm Good luck, Jim

Jim, you beat me to it. There is a lot of misinformation posted in this thread. The article Jim linked to above is a good read for all the guys who "think" they know what they are talking about. You know who you are.

Thanks for the interesting article. As to the pad/disc issue, I just called up the Porsche factory in Stuttgart and ATE (Continetal Teves) if Frankfurt, one of the foremost brake disc manufacturers in Europe. Both recommended changing the pads when renewing the discs. The issue with worn pads seems to be that the worn pad will only make contact with the disc in a few sports. This obviously results initially in reduced braking performance, but the real issue is that these spots get very hot, which can change the material structure in both the pad and the disc. If you absolutely must keep your old pads, ATE recommended to be gentle with your braking for the first 500mls or so, until the worn pads make full contact with the new disc. This seems to contradict what was said in above article. Also, according to ATE, deposit of brake pad material on the disc is not much of an issue with modern compounds. NB: All this information is concerning road use. Track use might be a completely different story. Cheers, Uwe