WARP(ed disc) DRIVE, or Why Does My Car Destroy Brake Discs?

Factual Questions
1

I have an older car, a 1989 Mercedes 300E. Many months ago, I had the brake pads and discs replaced (they were worn). Shortly after getting them replaced, I felt on braking the typical pulsing of braking against warped disks. This seemed to get worse, stepwise, over the months.

I took the car back to my repair place. (The rear discs were visibly warped, the front OK.) I asked if something mechanical, either in the car or mis-manufacturing of the discs could have caused this. Likely driving style, possibly in conjunction with bad timing in hitting a puddle after heating the discs could have warped them. That, or I left the parking brake on while driving. These causes seemed unlikely to me, but I didn’t think the problem would return.

A few weeks after the installation of new back rotors and pads, the pulsing returns. Again, the warping has gotten worse in a manner that seems stepwise.

So, I think that there may be a physical problem causing this. I think so for the following reasons:

[ul]
[li]I have had the car for many years and didn’t have this problem before.[/li][li]It has happened twice.[/li][li]My driving style did not change.[/li][li]I haven’t used the parking brake since the installation of the newest set of discs.[/li][li]I drive somewhat conservatively.[/li][/ul]

Any ideas of what to investigate what is causing this?

2

I hope you get an answer. The topic interests me as well.

3

Best guess is that you have a pair of hung calipers which aren’t releasing properly after the brakes are applied. This causes excess heating and warpage of the rotors.

4

I’d say that dances has pretty much nailed it. The only other possibilities that I can think of would be defective discs or a bad installation job. I’d have the calipers checked at the first opportunity, as brakes are not something you want to wait around to get fixed if there’s a problem.

5

Also, check the hoses that feed the brake fluid to the calipers. This happened to hubby’s car a while back - the hoses collapsed and it took a while for the fluid to flow back into the master cylinder, keeping the brakes riding the disks. The disks overheated, and warped. It also pretty much ruined the hub. We discovered the problem when he got a flat, and couldn’t remove the tire - it was pretty much welded to the hub.

Olive

6

I’ve often heard that lug nut tightening can be a critical factor in keeping discs from warping (depending on hub/rotor construction), and especially so for cars with aluminum wheels. Bear in mind that most mechanics greatly overtighten the lug nuts with an air wrench when reinstalling the wheels on you car.
http://free-auto-repair-advice.blogspot.com/2007/07/prevent-rotor-warpuse-proper-lug-nut.html
"Rotors can warp for several reasons: transfer of friction material from the pads to the rotor surface causing thickness variations, binding caliper slides that restrict pad release and keep the pad in contact with the rotor, causing it to overheat on one side, and improper lug nut tightening procedures. Lug nut torque is critical to maintaining rotor integrity. Here’s how it should be done:

Always tighten lug nuts with a torque wrench. Varying torque from one lug nut to another by as little as 5ft/lbs can cause rotor warp. Lubricating the stud threads can also cause differences in torque readings. So, NEVER lubricate studs. Set your torque wrench to ½ of the recommended torque and tighten all lug nuts in a star shaped pattern. Then reset your torque wrench to the full torque ratings and retighten all the lug nuts to the new torque. ©, Rick Muscoplat"

7

Thanks for all the responses so far. Does this described problem sometimes happen to the calipers on both sides in the rear of the car?

8

You said “repair place” rather than “dealer”.

The last time I replaced a rotor, NAPA had a choice of two replacement options. One cast in China, the other forged in Canada. The higher quality (forged) rotor was about 1/3 to half again more than the cheaper one. A casting that is not properly stress relieved prior to final machining is likely to warp the first time it gets hot.

9

It can, if both calipers are the same age, otherwise, it’s pretty unlikely.

10

That had crossed my mind. If that were the case, wouldn’t the front rotors be more likely to warp? Unless that’s what the repair guy thought, so bought cheapies for the rear!

11

I’m also going to say sticky sliders and/or cheap rotors. I was having this problem on the front rotors and my pads weren’t lasting very long. I removed the sliders and greased them up good (one took some work to clean up, it was locked up) and the problem went away. I was also using the less costly rotors so that may have played a part too.

12

I would second this as a possibility, especially where the car uses wheel bolts rather than lug nuts. Doesn’t Mercedes use wheel bolts?

13

This seems to be the correct answer.

I had assumed because the problem followed the same timeline as the first warping, the same warping problem was happening. My assumption was wrong. This time it was the front rotors warping.

So, here’s what happened in sequence.

[ol]
[li]Pads and rotors for all four wheels were replaced due to normal wear.[/li][li]Two weeks later the rear rotors started warping.[/li][li]Several months later the rear rotors were replaced.[/li][li]Two weeks later the front rotors started warping.[/li][li]The front ones have now been replaced.[/li][/ol]

I did have the repair guy check out the mechanical parts suggested here. All checked out OK, which makes sense becasue all signs now point to a complete set of rotors that were not cut out for this world.

Thanks for all the help!

14

Rear brake discs warped? Wow. Mail it in: the pads are probably slightly engaged all the time. Are the rear wheels covered in brake dust? They should be clean looking almost all the time.

The rear brakes do a paltry amount of work. Wow…warped rear disks = problem, wherein the pads are constantly pressing on them.

15

My brother had a Taurus that had that same problem, reoccurring. What it turned out to be was bad design by Ford, and simple oem rotors, no matter the quality, were overheating and warping. The last set of rotors he bought had vent holes in them, and he hasn’t had a rotor problem since.

16

My ex-wife kept warping rotors-turns out she was riding the brakes. Some other possibilities:
-cheap rotors; some aftermarket rotors are made in China-of recycled steel-these warp easily and cannot be machined true
-sticking pad
-bad driving habits-you can overheat and warp the discs by riding the brakes