How many of you guys,,, and how often get rotor warp.

My last 94 ( that was wrecked after 32 days ) had a bad brake pulse.

I picked up my new 94 form member Cavu this weekend and drove from Atlanta to Chicago without a problem.

It braked smoothly until I got a bit aggressive and braked hard and sure as chit there was the hard pulse again.

I am wondering if no one adjusts the rears and the fronts do all the work then warp.

Actually,,, do the rears self adjust on these or not?

any input?

 

The rears are disc brakes so they are self adjusting by there very nature. Do you have the 12" front brakes? My '94 seemed to have rotor warp after only about 5k miles when the brakes got good and hot. After cooling down, it wasn't noticable. I've since upgraded to the 13" setup and haven't experienced any warp.

 

I've gotten it several times on various cars/trucks. Never on my Corvette.

There are several conditions that may result in pedal feedback.

First, I believe the spec on rotors is around .005" runout at the middle of the rotor field. That is a lot of runout. I suspect many would feel some pedal feedback at .002-.004. Ballpark. So, if the wheels get torqued to the wrong value, it can warp the rotor. If you do anything to displace, warp, or otherwise damage the disk, you can get pedal feedback.

Another source if feedback is what is sometimes called material transfer deposits. Say some brake pad material transfers to the rotor. This can lead to one part of the rotor thicker than another part. The pad would "slide" over the high portion and then back down, thus causing the caliper/pistons to vary their position throughout the braking cycle.

Some manufacturers no longer suggest cutting rotors. Chrysler has some models with rotors about as cheap as cutting them. I think Ford also has some smaller disks really cheap. Under $23.00

A good lathe and operator should bring runout under .001". For non racing applications, I have no problem turning rotors. If you decide to cut the rotors, check the pads. If less than 50%, replace them. Make sure to follow the "bedding in" instructions for the pads.

I hate brake pedal feedback.

dlmeyers 90 coupe zf6 3pseed shocks

 

Stole my thunder

Up until last year I wouldn't have believed it but it is a myth.The brake pads need to bedded properly.Most of what we thought was brake warp was contamination on the disc.Proper bedding removes it.You need to do several medium pressures stops from 60-15mph till you smell the pads and mabey get some brake fade then one longer lighter brake stop and take it home to cool off or go on a road trip on the freeway.Works for me

 

This car is really strange,,,,,,, It just went for a ride,,, it was fine around town even from 55 down to a stop.

Jumped on the expressway, ran it up to ,,, well, never mind,,,, and LIGHT braking to slow down brought on the vibration. After that,,, I have a vibration braking from 55 MPH.

Very strange.

 

My experience also suggests uneven pad transfer. I would try resurfacing the rotors and carefully bedding them in.

 

I had the opposite happen. My car wouldnt pulsate when braking. It only pulsated upon accelerating. Replaced the rotors and the problem went away. I even bedded the pads the proper way as explained above. Both of thse rotors were new and I was told that it can happen anyhow.

 

This was a real eye-opener when I read it last year. But, when you think about it, it makes perfect, logical sense.
Metal distorts (warps) as a result of uneven heating (I have some heat-treating background). Brake rotors are heated very evenly when the brakes are applied, therefore they can't warp. Ever put a dial indicator on a "warped" rotor? There generally is no more runout than on a new one.
However, once the rotor is contaminiated by the pads, the only sure-fire cure is the same as if it WERE warped: turning.

Larry
code5coupe

 

Gentlemen,

The pedal pulsation equation is not solely related to runout, you need to be checking thickness variation around the rotor. One leads to the other. I've checked many aftermarket rotors out of the box and found them to be out of spec on thickness variation. I've obtained the longest life (in terms of pedal pulsation) from my brakes when I take a new rotor, dress it on the lathe to assure minimal thickness variation and then take the time to properly bed the pads.

-Chad