imgn tht

So I just picked up a 2004 Coupe Auto from a family member with 16,700 miles on it. Besides him nobody has ever driven this car and it was mostly suburb traffic, with the occassional highway sprint and a yearly jaunt from Chicago to Northern Michigan.

I drove it to work today and noticed the brake pedal (and seemingly the whole car) would pulsate when coming to a stop. It seemed to happen mostly at the end of the stopping procedure, say 10-15mph and slower. I also *thought* I heard a revolving whoosh while driving.

I've been around cars for some time now, and so my initial thought was warped rotors. I read a few posts on the forum stating the OEM units were prone to warping, but nobody wanted to fess up and actually call it warping? I talked to the previous owner and he has had the rotors turned by the dealer when it was practically new. Judging by others on here it doesn't take long for the issues to "resurface". Pun intended.

My question is...am I on the right track thinking this is a rotor issue, or could it just be pads?

I can replace the rotors myself and will forego the OEM ones in favor of something aftermarket with a better following and positive results. I found the Kinetic deal for slotted and cross-drilled from BrakeMotive(?) forum sponsor. Seems to be a lot of buyers, but any feedback on quality long term? I'm not racing, need these for daily driver and intend for these to last a few years so I don't have to replace again.

What are recommended pads (ceramic/semi-metallic) to go with the suggested rotors?

Thanks in advance!

Bill Curlee

Well,, if it were my car,, I would take it out on a SAFE and isolated road and do a few controlled 60 mph to 20 mph aggressive stops to resurface the brake pads and remove any deposits off the rotors. Once you do that allow them to cool off and do a few more. See if that corrects the pulsations.

Seen several lightly driven C5 & C6 Vettes get brake vibrations and it was due to build up on the pads and rotors. If the car sits a lot, rust can build up on the pads and rotors and embed into the pads. Some aggressive stops can burn off the debris.



IF,,,,, that doesn't resolve the issue,, I would disassemble the brakes and inspect the pads and rotors.

IF,,, you need to replace them, (and I don't see how that can be necessary at that low of mileage) I had very good results with the GM Performance pads and NAPA Premium rotors. I drive my 02 Z aggressively and they perform flawlessly.

NOTE,, I do not do HPDE events.. IF,, you do or plan to, you may want to step up the funds for a performance brake system... $$$$$$$$$$

If it just a fun daily driver or seldom driver,, the stock GM Performance pads will do outstanding.

My first brake pad and rotor replacement was accomplished at 40,000 miles.

BC

Supercharged111

FWIW my car has 103k miles and the rotors really look to be original. With the mileage and 4 track days (plus whatever the PO did), the rotors still aren't warped, so I don't see where the stockers would be prone to warping. I'd give Bill's method a whirl before spending any money.

SS2001SS

If cleaning the rotors as mentioned doesn't work, I would check the lateral runout of the rotors. My car did the same thing when I first got it. It had 75k miles on the original rotors, so I figured they were warped and replaced them.
Still got the pulsing brake pedal!
So after much research I learned the the Vette is prone to rotor runout. Especially if you do not get the rotor-to-hub surface COMPLETELY clean when replacing rotors.
Turned (used) and even brand new (perfectly straight) rotors can have runout when installed.

When checking the runout, it must be less than .002". If it is more than that you can "index" the rotors by pulling them off, rotating them, and re-installing on the lug studs. It took me a while with my dial indicator but you can figure out which way to rotate them to reduce the runout. If indexing doesn't work, they sell rotor shims that correct the condition (or at least bring the runout to within tolerance).

After a lengthy (because I didn't know the Vette was so sensitive to this) process, I was able to index my new rotors to within the tolerance (no shims) and the pulsing pedal went away completely.

imgn tht

Thanks for the responses and suggestions. I'll try Bill's suggestion first as soon as I can get it out to the correct road. If that doesn't work, I'll do some more inspection of the pads and rotors through disassembly and take it from there.

LoneStarFRC

Far too many brake rotors get condemned as "warped" when in fact they are NOT. I think that is one of the most common misdiagnoses of brake related issues, especially so-called "pulsating" brake pedals.

SS2001SS

Make sure you check the runout before putting the calipers and wheels back on and setting it on the ground. Been there and ended up pulling it apart twice.

imgn tht

I'm a bit of a newb for this specific procedure. How do I check for runout? What tools will I need and I'm looking for less than .002"? I saw the indexing comments in an earlier post, and have to say it was above my level of knowledge.

SS2001SS

I'm not the best a writing things up but:
I used a dial indicator clamped to the a arm.
Position the point of the indicator so that it is exactly 90* (perpiendicular) to the rotor surface about half inch or so from the edge of the rotor (while the rotor is bolted snugly to the hub).
Make sure the tip of the indicator is touching the rotor and zero the gauge.
Slowly turn the rotor and observe the indicator gauge.
You will probably be amazed at how much the gauge moves.
Ideally you want the gauge to be at zero on the lowest point of the rotor rotation.
The amount of travel measured by the gauge between the highest and lowest point is the lateral runout (LRO) of the rotor.
If it is more than .002 it will probably cause a vibration or pulsation felt in the brake pedal.
Here you go I just found this:
http://www.youtube.com/watch?v=H_1ySs7liS4
My indicator is different but the principle is the same.