: Brake pad transfer; vibration; cure?



6104696
06-27-11, 11:35 AM
Had a blast with the V2 at Vday5. the car performed perfectly, and was quite fast around the track. I did get the "overheating differential" warning about halfway into each session.

I also started to get a high-frequency vibration when applying the brakes at high speed, beginning in the middle of the second session when I was really starting to run the course "the right way." It felt/feels like, and looks like, brake pad transfer. No, silly me, I did not "bed" the brakes. Car has 5000 miles on it.

Anybody know of a good way to fix it, short of new rotors and pads? I had thought that it might clean off during normal street driving. Not yet. I have heard the following options:

1) Cleaning with Brakleen and a brillo pad;
2) Cleaning with Brakleen, a brillo pad, and a blowtorch (sounds like a good way to blow myself up);
3) Turning/milling the rotors (do places even do this any more?);
4) replacing the rotors;
5) replacing the rotors and the pads.

I know #5 would do the trick, and I know that the purists would recommend going all high-perf aftermarket parts. For 1 or 2 track days per year, though, I'm not sure if aftermarket is needed. But...if the factory stuff can't handle even one track day...maybe I need to?

Any thoughts?

Thanks in advance.

amunderdog
06-27-11, 12:25 PM
Sounds like you warped the rotors.
You can set up a dial indicator and check.

6104696
06-27-11, 12:50 PM
seems like it is too high frequency for warped rotors (I've had plenty of warped rotors on various cars)...and you can see the pad schmutz (this is an SAE-certified technical term) on the rotors. From what I can tell, it is a classic pad transfer problem. Just trying to figure out what to do about it.

rjoffe
06-27-11, 12:58 PM
pad schmutz (love it) can be easily removed by scotch-brite type pads on a drill, or other high speed tool.

Silver -V-
06-27-11, 07:10 PM
I found the OEM pads to leave a lot of pad transfer after a hard braking session. The best remedy to get the pad material off of your rotors - drive it around town for about a week. The material will clean off, and you will have a smooth rotor again. Next time, run a different pad with less material transfer.

thebigjimsho
06-27-11, 11:32 PM
pad schmutz (love it) can be easily removed by...or other high speed tool.Huh? I didn't even run...

baabootoo
06-28-11, 12:14 AM
They still turn rotors, and the best way is to have them done while ON the car.

EricVonHa
06-28-11, 01:43 AM
Don't waste any time with Brakleen and any manual scrubbing.

The best thing to do? Remove the pads and mark them so you know where they go back. There is a channel in the middle of the pad material. Take a small screwdriver and clean out that channel. Once the pads are back in; take the car out for a mile or two normal spin. Then, perform a handful of 60 to 10mph stops in a moderate fashion to build up some heat. We're not talking about high-heat threshold abs stops-- just moderate braking. And, don't stop the car during this. Don't sit at a light or stop sign or whatever with your foot on the brake. Fully stopping the car on a hot rotor will cause pad transfer. All you're looking to do is remove the material and even reduce the pad scarring of the rotor. Trust me, the pad scarring of the rotor will disappear in less than 2 tanks of gas under normal driving. However, if you wish to speed up the process, clean out the pad channels and do a few moderate braking exercises.

baabootoo
06-29-11, 12:36 AM
Well said.

6104696
06-29-11, 02:37 PM
yeah, it does seem to be reducing as I drive (though I have been mainly using the convertible since Vday...I think the V is STILL cooling down from the track :-)

I'll get some miles on it this weekend and hopefully I won't have to get my hands dirty. But I think I will think about some better pads for the next track day. I never had the pad transfer issue with 3-4 track days on the V1....but I am pretty sure though that the rotors on the V1 may have warped slightly during Vday 1.

EricVonHa
06-29-11, 05:49 PM
One important tech spec that's commonly overlooked is that the wheel bolt torque should be 150ft/lbs. Most rattle guns (and unknowing techs) do not know this is important. GM's spec for these bearings and wheel bolts is far above anything that is normally taken for granted. Most wheels don't get tightened past 100ft/lbs. And, that 30% reduction in torque could yield to premature rotor run out.

PGA2B
06-29-11, 05:57 PM
They still turn rotors, and the best way is to have them done while ON the car.

That is called "Pro Cut", they cut the rotors while on the car to prevent any run out. You can also sand the rotors lightly with Garnet Sandpaper to remove the pad material from them.

If you look up Pro Cut Brake Lathe on Google you can go to their website and there is a Dealer look up.

Chris__B
06-29-11, 11:20 PM
The BEST way to do it is to use a Flex-Hone (Google it) on the rotors. For the pads, lay them face down on 120 grit sandpaper on a very flat surface. Oscillate them until the pad surface is 100% dull and even looking. Shiny is bad.

The 2nd best way is to use Scotch-Brite and a ton of elbow grease on all rotor friction faces. Then the same as above for the pads.

Either way, re-bed the pads on the fresh rotor surface before going anywhere, especially on a track. Never, ever, ever use sandpaper on the rotors! It is impossible to keep the surface flat by hand.

Chris

baabootoo
06-30-11, 12:40 AM
One important tech spec that's commonly overlooked is that the wheel bolt torque should be 150ft/lbs. Most rattle guns (and unknowing techs) do not know this is important. GM's spec for these bearings and wheel bolts is far above anything that is normally taken for granted. Most wheels don't get tightened past 100ft/lbs. And, that 30% reduction in torque could yield to premature rotor run out.

I thought that it was 140, unless you had the wheel clicking issue, then they upped it to 158? Yeah, I wonder if they use calibrated torque wrenches too.

thebigjimsho
06-30-11, 01:06 AM
I'm just gonna say Vossen concave wheels. Figured every other thread has to be about Vossen wheels so why not another one? :bore:

PGA2B
06-30-11, 09:57 AM
Never, ever, ever use sandpaper on the rotors!

True! Use Fine or Ultra fine Garnet ONLY (as it is similar to Emery Cloth or a Scotch-Brite pad) and take off only the pad material. I didn't say to sand DOWN the rotors, just the pad material. You should be able to see it on the rotors. If you cant see the material then don't try this.

Chris__B
06-30-11, 01:45 PM
True! Use Fine or Ultra fine Garnet ONLY (as it is similar to Emery Cloth or a Scotch-Brite pad) and take off only the pad material. I didn't say to sand DOWN the rotors, just the pad material. You should be able to see it on the rotors. If you cant see the material then don't try this.
No worries. I just wanted to be very clear as I have found that people read forums in many different ways, often different than the poster had intended. It sounds like we are very much on the same page on this one!

rjoffe
06-30-11, 05:02 PM
Flex-Hone

Are you using the flex-hone with the rotor still on the car, or taking it off ?

baabootoo
07-01-11, 02:57 PM
Another good thing that has worked for me is the gasket removal pads you use on engine surfaces. It won't touch the metal, but clean all all else. Use it on an air tool.