slant911

I just recently purchased a 90' C4 Cab and the previous owner put cross drilled (turbo type) rotors on the car. Well after he spent some $2000 on that venture he apparently didn't think it was a good idea to not let the brake pads wear into the rotors. They are damaged and can't find any local machine shop that can turn them down. Does anyone know of a place I can send them to that can turn these rotors? One more question - Does anyone know what the specs are on these rotors on how far they can be turned (assuming someone can)? I'll measure tonight and see how thick they are now.

Thanks.

John

J-McDonald

I heard from my local Porsche mechanic that Porsche rotors may not be turned (I couldn't really get a straight answer out of him as to why). Instead, he insisted, they must be replaced. Given that rotors (even cross-drilled ones) aren't very expensive ($150/each or so), you may want to just replace them.

I'm sure that others can discuss the rationale for not turning the rotors.

slant911

I've heard the same story, but, It seems that someone must be able to turn these things. Can't tell me that all these racers in the world (Porsche and others) throw rotors away every so often. Also, ht ereason I ask about turning them down is because of the price of new ones. You indicate $150. I've not seen anything cheaper than $300-$350 a pop for the cross drilled ones.

Bill Gregory

I bought Porsche, not OEM, 930 Turbo rotors with cast in (better than drilled) holes for $120 (list $166) each from Hendrick Porsche (800-315-8193).

John McM

I've just replaced the front disc rotors on my 1993 Turbo 3.6 (cross drilled). The parts cost was US$333 for the pair; a pretty reasonable cost.

Given that the braking effort is mostly on the front discs, I wouldn't dream of turning them down, especially when new replacements are available at that cost

slant911

Since last post I've contacted Vertex. They apparently have cross drilled rotors for $109 each. The cast kind not drilled. I will probably opt for that. Thanks all.

Jeff Curtis

Hey Slant, www.theracestore.com - talk to Ralph if you call, they give a great deal on Sebro -or- Zimmerman cross-drilled rotors. FYI, us racers and DE guys DO throw away our rotors often, mine only last four weekends, then they break all the way through...I'm on my third set since May.

Is it just marks or inconsistencys in the rotors wear pattern that bothers you, or did we have a metal to metal situation?

If we did have a metal to metal, I understand your quest to just get them turned. Good luck on that one, although I wouldn't think it would be that difficult to find somebody, try Napa or a muffler/brakes place...just have them turn them until the "ugliness" is gone...wouldn't worry about thickness too much, 964 rotors are thick, having .010 taken off won't hurt a thing.

Adrian

Porsche do not approve the turning of their rotors. They achieve this by not providing any limits apart from wear limits. You are allowed 2mm reduction in thickness from new. From new the fronts are 28mm thick and the rears 24mm. Please do not forget that they are vented so it should be 1mm off the front face and 1mm of the rear face,
Ciao,
Adrian
911C4

slant911

Jeff,

It appears that there was some metal to metal contact at some point in time. The pads that are there now look fine, but, there are grooves etched in these things that indicate they let the brakes go to far sometime in the past. I will probably opt for new ones as I can not find any machine shop here that will do them.