Theory about brake disc warpage

[Instrument 41]

Just went through 2 sets of front brake rotors on my wifes Volvo. First set, high dollar Brembo's, after 4 weeks needed to be turned. 2 weeks later to warped to be turned. Replaced them with el cheapo O'Reily rotors, 3 weeks and all is well...
Got into a discussion with a buddy and believes that rotors don't warps in as much as they collect brake pad deposits, therefore creating the feeling that there is warping when, in his reality, its just build up on the rotors. What are your opinions about this??

[BlueSkyJaunte]

I agree...I especially make sure not to keep my foot mashed on the brake when stopped after a "spirited" slowdown. I read somewhere that it somehow sinters(?) the pad material right onto the disc.

Seems to have worked so far.

[stuartj]

I put Pagid Blacks in the front of an 86 911. They pads were properly bedded in by the book, and for the first three laps at the track, experienced brake bite like I had never known in that car. By lap 4, a judder developed, by lap 6 the judder was so severe it was unsettling the car on turn in.

The wise heads diagnosed pad material depoist. I agreed at the time, because the judder went away with normal driving, as the disks and pads dumped any build up. However, when the brakes were really being used, the judder returned. I think the rotors had been heat warped, the warp returning when the brakes got real temperature into them. Both front discs developed severe cracks some time later, and got replaced. Ive since stayed away from Pagids, figuring it was cheaper to burn a set of standard pads every track day than destroy rotors.

The mystery in your case- does your wife drive the Volvo hard nough to get suffiecnt heat build up to warp rotors? Or even develop pad material deposits? Something is awry.

[Instrument 41]

She been driving it for 4 years. And the only reason I changed them is that I was doing a strut, strut bearing replacement, and decided, since I was there to replace the well worn pads and rotors.

[cstreit]

Yep. "Warpage" is a LOT less common than uneven pad deposition.

When the brake pads and discs are cold, braking is accomplished by friction. However once warm most braking force is from the making and breaking of molecular bonds between the brake pads and the pad material in the disk itself.

Uneven pad deposition will result in a "warped" like feel.

[Don Ro]

Here's a good article on "The "Warped" Brake Disc and Other Myths of the Braking System"
.
http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

[Jims5543]

Originally posted by Instrument 41
Just went through 2 sets of front brake rotors on my wifes Volvo. First set, high dollar Brembo's, after 4 weeks needed to be turned. 2 weeks later to warped to be turned. Replaced them with el cheapo O'Reily rotors, 3 weeks and all is well...
Got into a discussion with a buddy and believes that rotors don't warps in as much as they collect brake pad deposits, therefore creating the feeling that there is warping when, in his reality, its just build up on the rotors. What are your opinions about this??

I had this problem with my Audi. I bet your Volvo is an Automatic.

Here is how they are warping.

When you do a track day what is the #1 rule so as not to warp your rotors. Stay off the brakes. Especially after a session, never set the parking brake.

What happens when you come off an interstate or freeway doing 70+ MPH and you brake to a hard stop at the end of the ramp? How much heat do you think you put into those rotors right there? Then you sit at a red light or in traffick with your foot planted on the brake letting that heat roast the rotor.

Once I got into the habit of taking the car out of drive and getting my foot off the brake pedal I never warped another rotor.

[Oh Haha]

I am using this same technique with my vehicles as well. It works. The first set of rotors were shot at 35,000 miles. I have 70,000 now and the brakes feel like new still. I do both highway and city driving daily.
When parking the 911 in the garage after a drive, I don't immediately set the parking brake. I leave it in gear and then after a couple of hours(or the next day if I forget) I set the brake.

My Mom just called me on her Hyundai XG 350 last night. She said her steering wheel shakes when braking. I just replaced her rotors with new in the spring. I don't think she has 5000 miles on them. How do you clean the deposits off the rotors?
Yes, she drives kind of on/off, on/off.

[greglepore]

On a 911 the parking brake has nothing to do with the service brake...

[Oh Haha]

You are correct Greg. I guess I don't really need to do that with the E-brake. Thanks.