Tippy

Unless you are a hardcore racer, turning street rotors is perfectly fine.

porsche-t

I witnessed the Ferrari shop turn the front rotors on my buddies 360.

himself

I also turned my cross-drilled rotors -> I turned them into solid + dimple rotors by PFC. And, those turned into DeMan slotted rotors on my GT3.

-td

cardsrule

general rule is if the "lip" is more that one millimeter then its time to get new rotors. The independent shop i use to work at turned rotors all the time but i refused to do it. Not good to go under min spec and its a Porsche not a Kia...we use the brakes a lot harder than most cars and why would you want to take material off the rotor. My .02 cents...

Marlon

I turn mine everyday and take a little bit of material off in the process. As a bonus the car slows and stops during the process.

IrocMan

I had some old AP Racing CD rotors turned, also, and never heard that CD rotors would not be turned before this day; even if the explanation above could make sense...

dresler

What's wrong with a lip if the rotors are within thickness spec????

Macster

As long as rotor thickness not at minimum CD rotors dissipate heat just fine. What's the difference between a rotor reaching a thickness -- still not yet at minimum -- by wear?

One problem is if CD rotors do not have drilled holes but cast then as rotor is turned cutting tool encounters cast scale which is hard and cutting tool can deflect a bit and each hole will have a tiny series dips after it.

Some shops use a grinder to grind the rotor surfaces and a grinding wheel less afffected by any casting scale in holes. IIRC some company makes a rotor grinder than mounts on car and can refinish rotor surfaces on car. I would hope the grinder has a superb vacuum system though to keep any grinding dust from getting on any suspension component or on car's glass or painted surfaces.

After refinishing rotors all holes should have enough chamfer so even if rotor wears down to its mininum thickness any casting scale can not come on contact with the pads.

If the pads encounter casting scale pad life will be short.

I'm pretty sure genuine Porsche CD rotors have holes cast in but are then drilled to remove scale or probably have enough hole chamfer to keep any casting scale in hole coming in contact with pads.

Sincerely,

Macster.

Van

I don't understand why people turn rotors in the first place... They're either close to the min thickness and deserve to be replaced, or they don't really need to be turned - it's just a way for a shop to charge you a little extra. (And, usually, since fixturing the rotors onto a lathe is a secondary operation (secondary to both the original machining process and to your "on-car lathe" - as Marlon points out) there will be an inherent alignment problem that will cause the "turned" rotor to be non-concentric and have more run-out than before.

Way back in the day, when rotors were quite narrow (and usually solid) they could warp - so turning them was useful in reducing that warp. But, in today's modern rotors (and especially well-designed high-performance ones), I feel it's a waste of good time and good money.

Marlon

C4SnNJ

Resurfaced mine at 40k. Vehicle now has 55k. Car initially had a really bad pulsation coming from the rear(verified by pulling up on the e-brake). Removed rotors and sent to a machine shop to resurface. Pulsation gone. They weren't really worn(well within spec.) but there was wavyness that you could feel when running your finger down the rotor. Cost $60 as compared to a couple of hundred. Spent the extra money on a new set of floor mats.

Van

The e-brake contacts a different part of the rotor... Turning the rotor would not effect any pulsating caused by the emergency brake.

medtech

+1