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Thanks Andy, if it was that simple I would. I live in Australia where my choices are pay dealer prices or source from overseas and add freight. As you can imagine freight on four rotors from RockAuto, Pelican or whoever adds considerably to the price,.
If you have a lip, how close are they to the wear limit?
I'd only skim as last resort and using someone who has a good rep. But I am sat in the privalaged land of pelican etc and understand you are seeking options.
I've done a lot of high speed driving in fast, heavy cars, along with a lot of abusive hard braking, and I'm with Churchill on this one. I won't say that warped rotors don't exist, but I haven't seen any. A very excellent paper on that topic, well worth reading is at this link:
Thanks for your replies. I was using the 'warping' as an example, my rotors are not warped but do have a lip. They still function well, maybe I should stop worrying about them but still I am curious as to whether or not they can be skimmed.
Thanks for your replies. I was using the 'warping' as an example, my rotors are not warped but do have a lip. They still function well, maybe I should stop worrying about them but still I am curious as to whether or not they can be skimmed.
Rotors can be skimmed as long as there is enough thickness left.
after skimming the rotor have to have a minimum thickness of: front: 30,6mm, rear: 22,6mm
New rotors are: front: 32mm, rear: 24mm, and the wear limit is front: 30,0mm, rear: 22,0mm
We only skimmed rotors if the rotors are heavily rusted (stored outside for a long time),
if the rotors are warped or if the surface is damaged due to worn brakepads (metal on metal).
in other cases just replace breakpads until the rotor reaches minimum thickness (or less) then just replace the rotor.
1) I had my rears skimmed years ago as the rear rotors suffered from corrosion on the inner face, maybe due to caliper plate lift, maybe as the car was a garage queen before my ownership. They are OEM discs and were skimmed within the tolerances as above.
My rotors - they also have the min thickness stamped after the part number:
Skimming rotors is a proper engineering practice - there's nothing wrong with doing it. If we didn't chuck away as much stuff as we do now, when it's within tolerance, the world wouldn't be in as much of a mess.
2) there's no such thing as a 'warped' ventilated rotor, unless you park your car too close to the sun.
However, various scenarios can happen that cause a build-up of pad material on the rotor, so that the rotors have high-points.... these high-points grab even more pad material, making the problem worse. This transmits a vibration through the car when braking. Solution? Skimming or replacing the rotor will do it, unless the owner is causing the issue by sitting with his foot on the pedal whilst stationary with hot discs... which means the new rotors 'warp' again....
(note that skimming might not work for the high-spots, as the rotor material can actually be changed by the original-problem-causing heat, so it tends to grab more pad material than the rest of the rotor, so they say)
Last edited by orangecurry; 01-19-2021 at 06:34 AM.
Reason: found some photos
1) I had my rears skimmed years ago as the rear rotors suffered from corrosion on the inner face, maybe due to caliper plate lift, maybe as the car was a garage queen before my ownership. They are OEM discs and were skimmed within the tolerances as above.
Skimming discs is a proper engineering practice - there's nothing wrong with doing it. If we didn't chuck away as much stuff as we do now, when it's within tolerance, the world wouldn't be in as much of a mess.
2) there's no such thing as a 'warped' ventilated rotor, unless you park your car too close to the sun.
However, various scenarios can happen that cause a build-up of pad material on the rotor, so that the rotors have high-points.... these high-points grab even more pad material, making the problem worse. This transmits a vibration through the car when braking. Solution? Skimming or replacing the rotor will do it, unless the owner is causing the issue by sitting with his foot on the pedal whilst stationary with hot discs... which means the new rotors 'warp' again....
(note that skimming might not work for the high-spots, as the rotor material can actually be changed by the original-problem-causing heat, so it tends to grab more pad material than the rest of the rotor, so they say)
With my 17 years of automotive professional experience i have a different view i believe.
1) if it aint broken, don't fix it.
If there is no reason to skim the rotors, why should you do it?
The labour costs money, and you remove all material to match the thinnest part of your rotors.
The minimum thickness stamped in your rotors is the minimum thickness of the rear rotors, you can use your rotors until 22mm thickness.
If you skim the rotors they have to be thicker (min 22,6mm), if you skim them on 22mm you would have to throw them away.
2) Ventilated rotors can warp beleive me.
Mostly caused by racing behaviour in rainy weather, the rotors get hot and a drive through a pool of water can causes the rotor to cool down from one side and the rotor gets warped. ones warped the only solutuon is replacing or skimming the rotor.
One time (on a SUV) the driver managed to get the rotor so hot, that the metal of the rotor turned blue and in the middle of the surface where the brakepads make contact the rotor was full of tiny cracks. this rotor was also warped. This guy drove his SUV daily with exesive speeds +200KM/H on the freeway and always waited to the last point to start braking, it is not designed to do that, and failure will occur.
Exessive heat causes the tension in the metal to change, and it will never return to its original chape. ventilated or not. the reason you see this less often on a porsche is because the brakes are much bigger en beter ventilated as a normal road car.
But if you ask the guys who drive porsche on the track they will definitly ones had a warped rotor in the past.
But I agree with those who say that if you drive and use your car as it should, you would probably never have a warped rotor.
Ok, im from Europe, and English is not my native language.
With warped, i understand: Bended or deformed out of its original chape.
if there is a miscommunication, i apologize.
Gert
OK that is my understand of 'warp' as well - have you read the article?
What article?
i was just replying to the questions in this thread.
The info i have given is my own knowledge, and specs about the thickness i took from the Porsche factory specs manual.
01-18-2021, 10:37 PM
To skim or not to skim....
