user 8430

I have removed my rotors and was planning on purchasing new ones. I am now debating wether I can just machine my existing rotors. They have a slight lip on the outer edge from wear. this alone wouldn't mean that they are not machineable, would it? Thanks.

early85944

What determines if they are machinable is there thickness. Somewhere on the rotor there is a minimum thickness stamped into the metal. If the rotors are thiner than this thickness they should not be turned. I am sure a 968 guru here on the board knows the rotor specs for your car.

user 8430

Thanks, I doubt I have the tool required for measuring the min. thickness, I will take them to the shop and I am sure they can measure it.

turbopop

There should be a minimum thickness dimension (in millimeters) stamped somewhere on each rotor. Using a caliper, the machinist will be able to tell immmediately if they can be turned. If they can't turn them, there should be no charge, so you have nothing to lose. At well under $20 per rotor, it's a lot cheaper to get them turned and just as good as purchasing new.

early85944

There is not special tool required per say. An easy way to estimate the thickness is by knocking the lip off of the rotor with a peice of sandpaper. Then use various sized opened end wrenchs to see which ones fit and which oned dont fit. This will give you a good idea of what the rotor thickness is. The easy way though is to get a micrometer than can reach past the lip of the rotor and then take a measurement. Not everyone carries a micrometer in there back pocket though.

dgz924s

Kgain968: If the rotors have never been turned and the brakes were never allowed to go metal to metal, on a 94, I would say you are good to go on turning the rotors. Sounds silly but if you can't get a O.D. micrometer I can ship mine to you to borrow. D

Brent 89 - GT

Turning rotors should be saved for those on tight budgets. It really is not a good solution compared to new rotors. The rotor is a heat sink. By turning it you remove material used to absorb and dissapate heat. You are also marginally thinner afterwards, all of this reduces the ability to resist warping. If the rotors have a lip on them, and you turn them down from there, whats left? If you drive the car hard at all you will likely kick yourself 10k miles down the road for not just replacing them. Another issue to consider is that many shops have poor equipment and/or operators that sometimes return not so true rotors after a turning. Unless you NEED to save the money, you are much further ahead to just replace the rotors.

user 8430

Thanks dgz924s for the offer and the rest of you for your advice. I had them turned today for $40 at a local brake specialty shop. They said they had plenty of depth left and did not foresee any problem with machining them, especially where the car is not tracked/raced etc. They said they detected no warps beforehand, anf that they were easily machined, and didn't take many turns at all to do. I can always get new ones (at $350 a set) I will try it and see what happens.

BartW

Did I read correctly, $40 to have rotors turned??? I thought I was getting ripped off when the local shop here started charging $6 instead of $5 per rotor, this is the going rate at most parts stores that I have been to. By the way, new rotors should be turned before being installed on a car as well, I don't think I have to tell you about manufacturers tolerances and that the only way to have them true is to turn them.

user 8430

Yup $10 each rotor ($15 canadian each) I thought that was a good deal. Next time I will ship them to Mich.

83na944

For future reference, PEP Boys were going to charge me about $10 each to turn my rotors, but htey measured them and they were too thin.

So I splurged on a new set for about $55 each. Not bad, considering I got 18 years out of the first set.

IceShark

I know brake engineers do not like the idea of turning used (or new) rotors.

There is always the reduced mass (heat sink) issue but the engineers real problem is the structure of the metal molecules related to the tempering the rotor has undergone.

Perhaps an engineer can explain in a more detailed fashion, but the bottom line is don't turn them, just replace, unless you are on a really tight budget.

triscadek

Maybe it was $10 because he told them it was a Porsche before they did it?

user 8430

I have had my rotors machined and they are now painted and ready for installation, check out pics here <a href="http://63.136.85.109/forum/topic.asp?TOPIC_ID=2486" target="_blank">http://63.136.85.109/forum/topic.asp?TOPIC_ID=2486</a> or here as well with other pics of my car <a href="http://hobbystage.net/porsche/polar/" target="_blank">http://hobbystage.net/porsche/polar/</a> When I called for the quote I didn't mention what kind of rotors they were