95 Carerra

While my pads on my 95 993 are ok, the rotors are getting to the point, I believe, where they may need replacing. Couple of questions:

- My rotors do have a slight lip at the outer rim. Someone told that that once this happens, I should be on the look out to replace. How big is this lip allowed to get before getting into trouble? Or is the thickness of the rotor the key, and how thin should it not be allowed to get?

- Is there a DIY website for rotor and pad replacement? P-car doesn't seem to have this topic, nor rennlist (although it has website link problems at the moment)

Thank you.

RallyJon

Yes. 30mm.

Also, I noticed the inside face of my rotors wore more quickly than the outside. So they may need replacement even if there's little apparent wear on the outside.

TheOtherEric

Porsche also says to replace if the cracks reach a certain length. I think it's 7mm in front, but you should do a search to confirm, unless somebody else knows offhand.

An additional replacement criteria is if the cracks in the holes start connecting to adjacent holes. Or if the cracks start extending out to the rim of the rotor.

95 C4 993

Had new rotors and pads at 30k and most recently 57k. Miles probably dont mean as much as actual wear. My mechanic mentioned it a few times starting at 49k to replace the fronts. I had them turned 39k. The previous set up was Zimmerman and not sure what the pads were but whatever they were, they are a little loud. Im now with OEM and Textar pads. They didnt last that long either.

As far as DIY, Im sure there are several links on this forum. Im not a DIY person.

95 C4 993

The Zimmerman set up didnt last that long is what I meant.

geolab

As long as your pads are OK, there is no problem.
A small lip on the outer edge of a disc brake is normal wear sign.
RallyJon gave you the limit porsche recommends not to surpass.
New disc brakes come with a 33mm thickness.
A 1.5 mm lip on each side will give you an idea that your discs are to be changed.
Be aware that if you change to new discs, you have to put new pads, and never the old ones.
As for DIY, it is exactly as changing any disc brakes on any car.
One small detail, is to sand extensively the area where your new disc brake will mount.
its the flat area on the wheel hub where the wheel threaded bolts hang out.
Usually this area is slightly rusted and should be well cleaned.
If not, you may risk wobbling while braking.

TheOtherEric

I disagree. Using old pads with new rotors is perfectly fine.

Jim

According to the Porsche Service Manual, the disks are 32mm new, and the minimum acceptable thickness is 30mm. They can be machined as long as both sides are machined symmetrically. (I've never heard of anyone wanting to do this). If the lip is more than 1mm on either side, you should replace. Agree that old pads will fit new rotors quickly, (after a few hot stops), but "as long as you're in there...."

geolab

If you say so

FGL28

I think while you are monkeying with the rotors you might as well replace the pads. But I am of the one trip is better than two school.

Sooner

Here's the DIY from P-car. Not sure how you missed it. http://p-car.com/diy/brakepads/

Mark in Baltimore

I've put in new rotors with old pads all of the time and not had any issues. Ideally, though, I'd want to put all-new components in.

From what I've seen, I think the problem is that grooving in both rotor and pad can occur that can be exacerbated by a grooved pad that alters a new rotor. I wonder how deep the grooves would get if you kept on putting on grooved pads with new rotors over the course of ten swaps?

TheOtherEric

Instead of just acting dismissive, why don't you try posting some evidence that PAG recommends always replacing pads when new rotors are installed?

TheOtherEric

The workshop manual states that when you install new pads (onto existing rotors), the pads will adapt to the uneven profile of the rotors pretty quickly. I think their point was that the rotor's holes (and otherwise "high abrasiveness" of the rotors) help that process. At any rate, i think it's safe to say that a pad with uneven profile (i.e. a used pad) will adapt pretty quickly to match your new flat rotors.

chris walrod

Its highly recommended to bed new rotors with old pads, and opposite as well..