Resurfacing brake rotors
Thread Starter
Pro
Joined: Jun 2005
Posts: 538
Likes: 41
From: Alameda CA
Resurfacing brake rotors
I have a 2000 4th generation Camaro that I converted to C5 Corvette front brakes a few years ago:Recently I noticed a vibration under braking at freeway speeds. I suspected the rotors so I checked the runout. I measured 0.003" on the LF and 0.001" on the RF. The spec says 0.005" and higher should be surfaced but I decided to have them done anyway.
Apparently that was a huge mistake.
I found a local machine shop with good yelp reviews and was charged $20/each. I got them back today, installed them and found the runout on the LF was 0.015" and the RF was 0.013". WTF? You can even see on one of the surfaces a small area that was not machined at all -- a good indication that something is way off with his brake lathe.
The rotors measured > 33.0mm when I took them in and now they're down to 31.5. Spec says they can only be turned down to 30.3.
I know everybody says rotors are cheap, just get new ones every time. Well, these had never been turned and didn't have many miles on them. I've had rotors surfaced before without any drama. I guess I'll take them back and give the guy another shot and if he can't do it on the second try, ask for my $40 back? Or maybe declare these shot and ask for my money?
Apparently that was a huge mistake.
I found a local machine shop with good yelp reviews and was charged $20/each. I got them back today, installed them and found the runout on the LF was 0.015" and the RF was 0.013". WTF? You can even see on one of the surfaces a small area that was not machined at all -- a good indication that something is way off with his brake lathe.
The rotors measured > 33.0mm when I took them in and now they're down to 31.5. Spec says they can only be turned down to 30.3.
I know everybody says rotors are cheap, just get new ones every time. Well, these had never been turned and didn't have many miles on them. I've had rotors surfaced before without any drama. I guess I'll take them back and give the guy another shot and if he can't do it on the second try, ask for my $40 back? Or maybe declare these shot and ask for my money?
Drifting
Joined: Dec 2015
Posts: 1,410
Likes: 414
From: Germantown Maryland
Many times, if not most, the vibration isn't from rotor runout but from uneven brake deposition creating areas of variable friction. With your original numbers I suspect that's what was going on. Google the issue and you will see how it looks. If you stop a few time with brakes hot and hold down the pedal, like at a traffic light, you can develop this issue. That can usually be fixed by lightly sanding the rotor surfaces to remove the depositions.
BTW, I did that same C5 front brake mod to my 1994 Camaro Z28 that I sold when I got my C7. That was a good setup on the f-body. The rotors cost $25.
BTW, I did that same C5 front brake mod to my 1994 Camaro Z28 that I sold when I got my C7. That was a good setup on the f-body. The rotors cost $25.
Last edited by raylo; Oct 12, 2016 at 08:33 PM.
Drifting
Joined: Oct 2002
Posts: 1,335
Likes: 76
From: Bedford Va.
I used to have a good brake shop by me, gone now but your shop likely just set the cutting bit up on the rotor and started cutting.
They should have set the bit up to the rotors low spot but not cutting material at the low spot. They run the cutter to remove the high surface. then do a very light 2nd cut on the whole rotor.
Most don't want to spend the time.
Did you rotate or change wheels recently? I wire brush the wheel and rotor hub contact surface when moving tires/wheels.
torque the wheels also no air guns here.
They should have set the bit up to the rotors low spot but not cutting material at the low spot. They run the cutter to remove the high surface. then do a very light 2nd cut on the whole rotor.
Most don't want to spend the time.
Did you rotate or change wheels recently? I wire brush the wheel and rotor hub contact surface when moving tires/wheels.
torque the wheels also no air guns here.
Last edited by Mr. Jones; Oct 14, 2016 at 11:47 AM.
Thread Starter
Pro
Joined: Jun 2005
Posts: 538
Likes: 41
From: Alameda CA
That sounds sounds like cause (thanks!)
I went back and explained the rotors were now out of spec and he offered to give me a refund. Doubting his ability to do better with a second try I gladly accepted. New rotors are inbound via amazon.
Amusingly, he claimed both rotors were "badly warped" which seems unlikely since I measured 0.001 to 0.002" run-out before. And the fact that both were so consistently out after machining really points to a problem with the brake lathe setup.
Although the wheels have been off during the period when I was noticing the vibration, I haven't rotated in awhile (I only do a couple K miles per year with this car).
I went back and explained the rotors were now out of spec and he offered to give me a refund. Doubting his ability to do better with a second try I gladly accepted. New rotors are inbound via amazon.
Amusingly, he claimed both rotors were "badly warped" which seems unlikely since I measured 0.001 to 0.002" run-out before. And the fact that both were so consistently out after machining really points to a problem with the brake lathe setup.
Although the wheels have been off during the period when I was noticing the vibration, I haven't rotated in awhile (I only do a couple K miles per year with this car).
