spm2001

Just finished installing brand new Delco Durastop slotted/drilled front rotors, EBC red front pads, Goodridge brake hoses all around, and pressure bleeding the system (Motive products, Motul fluid). Setup is intended for street + occasional (road track) driver's school. Everything works ok, no leaks, but with only a ride to work and back so far I'm getting heavy brake pulsations on light to moderate braking, haven't stomped on it real hard yet. Seems like one or two pulses per tire rotation.

Any ideas? Is this typical for break-in on this setup? There was no pulsation before this, even though my front rotors and pads were shot. I'm a moderately experienced home mechanic, have changed rotors/pads on other cars many times, flushed the brakes on the Vette a few times before, etc.

thanks,

Steve

gonbad

The rotors float on the hub, so it sounds like either the rotors were defective and came to you with excessive runout or they are not laying up flush to the hub. Two things could cause this. 1. improper wheel torque and/or 2. the hub was not clean causing an uneven surface. Most likely it is the second one. Unfortunately the only way to fix it is to pull the rotors off and clean the hub surfuce with a wire brush. While you have them off run them up to a brake shop and have them checked for runout.




[Modified by gonbad, 5:42 PM 10/14/2003]

Mike Siska

Had this problem happen when I had the $28.00 napa rotors installed. Had the rotors turned and no problem now!! :cheers:

carpe dm

I agree with "gonbad"; take 'em apart, clean and replace. Did you do a proper pad break-in? That could be partof the problem too. :yesnod: :)

Richin Chicago

Just want to emphasize what others have said. First place to check is where the rotor meets the hub. A small amount of material there can cause a big disc runout.

silverz06vette

http://www.stoptech.com/whitepapers/...otors_myth.htm

Smokin Joe

Read this thread and pass to everyone you know that drives cars. :iagree:

Cobra4B

Woah :eek: lots of good brake info there.... guess I need to use my brakes a bit harder so that transfer layer can come back :yesnod:

CRUZMISL

Exactly, lay the boots to those things and watch your troubles disappear :) Just be sure you've broken them in properly.

spm2001

Getting back to my original problem, I disassembled each side of the front brakes, didn't find any obvious grunge on hubs or rear of new rotors, wirebrushed anyhow, couldn't feel any irregularities with my bare hand, and put back together very carefully. Did left side one day, right side another day. just to see which one might have been causing it.

No luck, problem remains. I'm reasonably convinced it is a bad new rotor. Also, with the car jacked up but wheels still on and bolted tight, if I hand rotate the right front wheel, for part of a single turn it binds a little bit on brake pads, but for the rest of that single turn it is completely free. Something is causing it to bind, hence generate the pulsations. I marked the area that was binding on the rotor hat, and realized I could (but didn't) confirm that the problem was the rotor by uninstalling again, reinstalling but shifting it half a turn on the hub, then spinning by hand and marking again. Same marks would indicate rotor, different ones would indicate something in the mating surface between hub and rotor.

Next step, I'm going to try another new rotor on that side, a cheap one until I determine that it fixes the problem. Assuming that works, I'll have to then try to convince GM that their expensive brand new Durastop rotor was bad. Or eat the cost.

Steve

CHJ In Virginia

The best teat method is to use a dial indicator on the rotor. Any decent brake shop can run the test for you cheap. The indicator is clamped to the caliper bridge and the pointer set on the rotor friction surface. The dial is set to "0" and the rotor is then rotated a full turn. Watching the dial indicator needle you will get a + or - reading on runout. Anything more than .003 inches is unacceptable and will cause a pulsation as you describe. I have seen MANY new out of the box GM rotors have runout in excess of .010. :mad

martin97c5

first i would try another set of rotors on there, do you know anyone with a c5 thst lives in your area??? I live in peabody MA if you wanna come by you can try out my rotors.
This may sound a little weird because this dosent have to do with a corvette. But I have an explorer and on eof the wheel studs broke off. so i brought it to a dealer to have a new one put on. I pick up my car the next day and mike brake are doin the same thing yours are. My dad sitting in the pasenger seat while im driving says look at your back wheel its wobbling!! So i sat in the passenger seat and looked at my back right wheel and indeed the wheel was wobbling by an inch. at first i thought my rim was bent. It ended up being a bad lugnut that did everything. Because it was skinny at one end so it went more through the wheel than the others which made that lugnut push of the flange. Does this make any sence??
Anyways I would have some one sit in your car and look at the front and rear wheels while your driving and you should look at the wheels on your side while your driving and see if they wobble at all becsuse if they do than that would cause the disc to not be straight as well.
Martin

BlackC5Vette

:iagree: Very good info!

spm2001

Original problem was an out-of-round brand new Delco DuraStop rotor. I had it turned -- didn't know that a slotted drilled rotor could be turned - and everything is fine now.

BTW, after trying to get this resolved thru local Chevy dealer, who is supposed to provide GMParts warranty service, found out that any Chevy 'performance' parts have absolutely no guarantee once installed.

Is it unreasonable to expect a brand new rotor to be properly 'in round'?

rownvette

I replaced my front rotors in September to eliminate pulsations from the original rotors with 96,000 miles on them. The new rotors and pads were properly broken in and seemed fine for a couple of weeks until I braked for an exit off the highway and the pulsations came back big time. Checked wheel tightness, etc., and everything was fine. Talked to the parts store and told them I suspected a bad rotor and they ordered replacements. C5 rotors are specific for the left and right sides of the car.

When they were installed in September, they were verified for the proper side by part number, but when installing the replacement rotors, it was discovered that, even though I had the right part numbers on the correct sides, I had, in fact, received two right side rotors in September, one with an incorrect part number on the package. With a right side rotor on the left side, the the rotor vanes on the left rotor were not cooling properly and it warped from overheating on that side.

When installing the new rotors today, we again verified the correct part numbers were being installed on the proper sides, but guess what - Even though I had the correct part numbers, this time I wound up with two left front rotors.

When installing replacement rotors, I highly recommend verifying that you do have a left and right rotor, especially with all of the replacement brake parts coming from China now.

$$$frumnuttin'

wow, sounds like the folks selling these things have no clue that there are different part numbers....

rownvette

You got that right... And the people packaging the things can't tell the difference.

striper

I find it rediculous that GM can't get brake rotors packaged correctly. If anyone is looking for an inexpensive set of drilled, slotted rotors that also come zinc plated, then try the sets available from www.brakemotive.com. They even come with new pads, too, for $180 shipping included. I don't represent the company, I'm just one of many satisfied customers who were pleasantly surprised how good these rotors are for the price. The braking performance has been excellent. Also, I have them on for many months now and there is no pulsating.

CactusCat

Big Plus for brakemotive. He gives a discount to forum members (message him to let him know) and his products are great as well. Haven't seen anyone able to touch his price. Many satisfied members using his products.

rownvette

Just checked Brakemotives prices - $189 for 4 rotors AND pads? Know I won't be going back to my local parts store for brakes again!