tici

iTrader: (1)

500 miles ago I installed a set of front Wagner rotors and Wagner termoquite pads.

Up to about 40 mph it's fine, but if I brake from a higher speed they start to vibrate (= shaking).
The hotter the worst.

Have I already warped them?

Or is that an irregular deposit on the rotors?

The rotors aren't shiny, they have a gray layer on them ,similar to the pad color (???)


Any Idea?

Thanks - Stefano

xpndbl3

iTrader: (23)

sounds like you overheated them and need to have them cut and put on new pads. Possibly also due to a sticking caliper as well, or a failed rubber brake hose. Jack up the car, depress the brake pedal and then climb out and see if the wheel spins. If not something is hanging up

chicane

It is a thermal variation, aka TV, from getting hot and having your foot on the brake at a stop.

Read this: http://www.stoptech.com/tech_info/wp...rakedisk.shtml and this: http://www.stoptech.com/tech_info/wp_padremoval.shtml

There is no reason to 'cut' a new rotor... in fact there is no reason to 'cut' a rotor at all... unless you run a pad compound that is so aggressive that it grroves the rotor surface.

gollum

iTrader: (1)

Brake rotors WILL warp, regardless of what I just read regarding thermal variation. Simply take a dial indicator with magnetic base and check rotor run out (no more than .003" is good). Autozone sells replacement rotors very cheap and be sure to break in new pads properly to prevent thermal variation also.

tici

iTrader: (1)

I checked the runout and saw a max. of 0.004"
I then removed the rotors and saw a layer of rust on the hubs that I forgot to remove during the installation (forgot... read: TOO LAZY!).
I then brushed the hubs to the metal and reinstalled the rotors.

The runout is now 0.0012" one side and 0.0020" the other. So that's should be OK. There's no thickness variation.

However... when the brakes are cold they are 100% OK (no vibrations), but as soon they warm up the vibrations are back

I talked to Sam Strano asking about different pads. His opinion is that the rotors warp above a certain temperature. I can turn them as much as I want: they will still warp.

Maybe it's an irregular layer of pads compound...

What do you guys think?

gollum

iTrader: (1)

Check out the return policy on your new rotors, sometimes you can get a 100% refund at places like Autozone.

Try new rotors and follow proper break in procedure:

"There is only one way to prevent this sort of thing - following proper break in procedures for both pad and disc and use the correct pad for your driving style and conditions. All high performance after market discs and pads should come with both installation and break in instructions. The procedures are very similar between manufacturers. With respect to the pads, the bonding resins must be burned off relatively slowly to avoid both fade and uneven deposits. The procedure is several stops of increasing severity with a brief cooling period between them. After the last stop, the system should be allowed to cool to ambient temperature. Typically, a series of ten increasingly hard stops from 60mph to 5 mph with normal acceleration in between should get the job done for a high performance street pad. During pad or disc break-in, do not come to a complete stop, so plan where and when you do this procedure with care and concern for yourself and the safety of others. If you come to a complete stop before the break-in process is completed there is the chance for non-uniform pad material transfer or pad imprinting to take place and the results will be what the whole process is trying to avoid. Game over.

In terms of stop severity, an ABS active stop would typically be around 0.9 G’s and above, depending on the vehicle. What you want to do is stop at a rate around 0.7

to 0.9 G's. That is a deceleration rate near but below lock up or ABS intervention. You should begin to smell pads at the 5th to 7th stop and the smell should diminish before the last stop. A powdery gray area will become visible on the edge of the pad (actually the edge of the friction material in contact with the disc - not the backing plate) where the paint and resins of the pad are burning off. When the gray area on the edges of the pads are about 1/8" deep, the pad is bedded."

I once had a pair of new front factory rotors stress relieved by 300 BELOW CRYOGENICS...cost $50.00. This worked for me...no more warpage.

gollum

iTrader: (1)

This problem is common in our Fbody cars. My current 2002 SS Camaro with OEM brakes has a slight shaking once pads are fully warmed up also. I recently purchased new rotors and carbon metallic pads from Autozone because of their verygood return policy. I will install these soon.

chicane

So you are saying that just because you cannot see pad material build-up on a rotor... its warped ?? And BTW, its not a "thermal" variation... its a thickness variation. The pad material alone can and just might be more than 0.003"...

A simple change of pad compounds can null this proble without any other component change. Besides, green bedding a set of rotors and a set green pads is a huge no-no. Allow me to quote, your quote:

That is the biggest contributor to thickness variation in a "green" situation.

Tici- Another thing to check is the hubs themselves. I have found that during cold operation the issue was not noticable... but after warm up, the bearing pre-load went away an induced a noticable shimmy under braking. After replacing the bad hub... the problem went away. So... I must ask, what years is your chassis, how many miles and have the front hubs ever been replaced ??

gollum

iTrader: (1)

Stress relieved Frozen rotors do help!

http://www.frozenrotors.com/pages/brakefaq.php


http://www.tirerack.com/brakes/brake...ar=&perfCode=A

http://www.tirerack.com/brakes/resul...2&autoModClar=

tici

iTrader: (1)

This is a 98, 75000 miles and still original hubs.
While checking the runout I was able to change the value by +/- 0.002" by hand just pulling and pushing at the rotors. Maybe the bearings...

I tried to remove a hub: the bolts are easy to remove, but the hub itself is locked in the seat. Rust?

How much does a hub cost? Does it include the ABS sensor? Or can I reuse the old sensor? Is there a particular procedure to remove the hub?

Sneakyws6

Jesh before you go and start throwing money into this car do the simple thing first, have shop turn the rotors and have them start by taking the smallest amount off they can until you get the rotor surface back to lever again.

I have heard several shops say that brand new rotors have came out of tolerance from the factory, the heat in the rotor will cause the metal to expand and make the issue more prone as they heat up.

I would turn the rotors first, do some light driving and braking and make sure the problem is resolved or if it is still there before you go and replace the hubs.

Some new rotors are just junk, my Formula warped the stock rotors by 2000, 5000, 8000, 12,000 miles before I got rid of them and replaced them with Powerstop drilled. Ran those for 45,000 miles before I changed the pads and turned the fronts. Just replaced them last month with a set of Baer Decelerators and soe mnew pads at 81,000 miles.