Rotor tolerances
Thread Starter
Le Mans Master
Joined: Jul 2004
Posts: 6,248
Likes: 4
From: Lancaster PA
Rotor tolerances
I had a front rotor turned down yesterday at a local garage. I watched him and he didn't use a micrometer. I asked him about it and he said it will be good. I brought it home , measured it and it's 1.208" to 1.202". Is 6 thousandth acceptable ?
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
I think not, but for three reasons.
1) the minimum thickness after machining is 1.215 (verified correct)
2) if you're measuring the rotor off the hub. 006" runout is crap workmanship- unacceptable.
3) if you're measuring it on the hub, it was a mistake to have it turned separately from the hub as you now have .006" runout to deal with, plus the under min thickness.
C3 brakes are a one of a kind animal. 99.9% of garages have no clue how to work on them and you get to pay for their mistakes. Sorry.
1) the minimum thickness after machining is 1.215 (verified correct)
2) if you're measuring the rotor off the hub. 006" runout is crap workmanship- unacceptable.
3) if you're measuring it on the hub, it was a mistake to have it turned separately from the hub as you now have .006" runout to deal with, plus the under min thickness.
C3 brakes are a one of a kind animal. 99.9% of garages have no clue how to work on them and you get to pay for their mistakes. Sorry.
Last edited by Mike Ward; Dec 10, 2009 at 02:03 PM. Reason: corrected min thickness dimension
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The guy was a 'hack' and just did what he always did...which is what "Joe" showed him how to do 12 years ago. Take it back to the shop with along with the measurements you made and the 'service' specs for the rotor [in the Chevy Chassis Service Manual data section]. If the rotor was too thin to rework anyway, just pitch it and consider it a "learning experience".
Premium Supporting Vendor
Joined: May 2000
Posts: 4,312
Likes: 70
From: Clearwater FL
Min thickness is 1.215. After that it's junk. 6 thou is to much for a runout especially in the rear. After the rotor is cut, you should hit it with a DA.
Check out this link. Just click the small or large version.
http://www.oeqf.com/techinfo/index.htm
Check out this link. Just click the small or large version.
http://www.oeqf.com/techinfo/index.htm
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
rotor
Perhaps you do not know about professional Corvette services offered in your own state. www.bairs.com For any rotor or bearing service their services could save you money based on your previous experience of ruined parts and services.
I learned of Bairs services in the late 80's, if I had known/used their services/parts in 1974 I would of saved lots of money/down time/my labor and enjoyed my original owner 1970 Corvette a lot more.
I learned of Bairs services in the late 80's, if I had known/used their services/parts in 1974 I would of saved lots of money/down time/my labor and enjoyed my original owner 1970 Corvette a lot more.
Last edited by 70ZZ3 96LT4; Dec 10, 2009 at 10:34 AM.
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Burning Brakes
Joined: Apr 2008
Posts: 825
Likes: 40
From: Glasgow, Scotland
Min thickness is 1.215. After that it's junk. 6 thou is to much for a runout especially in the rear. After the rotor is cut, you should hit it with a DA.
Check out this link. Just click the small or large version.
http://www.oeqf.com/techinfo/index.htm
Check out this link. Just click the small or large version.
http://www.oeqf.com/techinfo/index.htm
dave
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
As measured on the standard brake lathe or mounted ready to go on a hub?
Ha ha! Trick question! C3 Corvette rotors should never be machined on a standard machine but always while attached to the hub or spindle.
Final installed runout as mounted on the car should be less than .003" especially on the rear.
Ha ha! Trick question! C3 Corvette rotors should never be machined on a standard machine but always while attached to the hub or spindle.
Final installed runout as mounted on the car should be less than .003" especially on the rear.
Thread Starter
Le Mans Master
Joined: Jul 2004
Posts: 6,248
Likes: 4
From: Lancaster PA
Stopped and talked to the shop manager. Told him they were out .006" and undersize according to specs. He said my expectations are unrealistic. No refund. Threw it in his trash bin and walked out. $18 no big deal but extremely aggravating.
Thread Starter
Le Mans Master
Joined: Jul 2004
Posts: 6,248
Likes: 4
From: Lancaster PA
Racer
Joined: Nov 2009
Posts: 486
Likes: 1
I was in a similar situation between turning the rotors and buying new ones. I bought new ones for $40. Twice as much but least there was no headache and stupid people doing what they did to you.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Instructor
Joined: Oct 2008
Posts: 212
Likes: 0
From: Central llinois
Not a lot of money, but I think I would have made a big deal of it anyway. If these guys are going to turn rotors, they should at very least take the time to look up what the minimum thickness is and use a micrometer. Thats just a basic step, not an expectation, crap, its stamped into the rotor half the time. At least it was a really expensive lesson learned...
