RACER

One thing is for sure, there would be a buildup of brake pad material on the spot where the pad contact's the rotor with the parking brake set on a very hot rotor. This slight build up is just enough to cause a localized hot spot. This mean's that with every rotation, the buildup will get progressively worse. This is known as cementite.

Jasonoff

Lots of ways. Most commonly heat.

You make a couple long stops on the hwy and lastly a long one coming off the ramp then sit with your foot on the brakes at the end. Nice HOT rotor cooling down with who konws how much clamping pressure over a 1/4 of the surface.

With an inpact wrench. (more so if you don't have those set screws to hold the rotor on nice and tight). Your rotor slightly slides off and someone fires on the wheel with the rotor off center.

JohnE

thanks for the advice.. The warping I got was not due to impact wrench or holding the brake pad on a hot rotor. One day I was driving fast as usual, had to brake from a high speed (110ish?) to 70mph, somewhere during that particular slowdown the shudder started. My car has about 36k miles on it, not sure why mileage would affect the rotors warping under high heat. Without having a caliper (? the tool to shown in the service manual) to measure the rotors, is there any other easy way to tell which set of rotors are out of spec (front or back)? Also, do you just drop these off at any Pep boys, Napa, etc and they will do a decent job? Last time I needed new rotors, I just bought new OEM and replaced.

pantyraider

Rotors don't warp. It's a myth. It's exactly what AusS2000 said, uneven pad deposits. Check this link:

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

Jasonoff

^ If you say so. I think I have a "warped" rear rotor lying around if you want me to send it to you

I've also come to witness a crushed rotor. After a good 40min track session they had their foot stomped on the brake stopped on pit lane waiting to park and the pad left an impression in the front rotor. (it was on a domestic though )

I agree a "slight" vibration is probably that but when its a violent vibration she's warped. Think about it. A single piston caliper that's not 100% functional pushing on one side of the rotor rather than both sides equally. That's alot of single sided pressure on a hot rotor don't you think. How many of you rebulid your calipers once a year?

xviper

I'm going to have to disagree with what's said in that link. I've personally seen a warped rotor get turned. It definately was NOT brake pad material getting honed off. That "mythbuster" is a myth.

mikegarrison

Sorry, I was doing my best to ignore this subject, but this is completely W-R-O-N-G.

1) "Rotor warp" is actually due to uneven transfer of brake pad material to the rotor, rather than a warpage of the shape of the rotor. When you clamp hot brake pads onto a hot rotor, some of the pad material sticks to the rotor. After that, you feel that pad material as a 1/rev vibration.

2) Those little set screws are for holding the rotor in place when the wheel is off. They have no effect on the rotor either way when the wheel is on.

3) Nor does it matter whether you tighten the lugs with an impact wrench or by hand.

xviper

Only if the impact wrench incorporates a torque stick of the correct torque limit and the "by hand" uses a torque wrench.
It wouldn't be a good thing if the lugnuts varied in torque from 80 to 200.

mikegarrison

The "at the correct torque" was supposed to be implicit. Nevertheless, it would not be the rotor which failed in that scenario. It would be the studs.

Metal can bend, sure, but my engineering intuition just screams out that clamping down on a hot rotor will not warp it. Crack it, yes. Warp it? I just don't think so. I'm not saying it's impossible, just that it's much more unlikely than the well-known and well-documented pad material deposition phenomenon.

The caliper is free to float in and out, so that wouldn't be the issue. The only issue would be radial thermal growth (shrinkage, in this case).

But anyway, you should be able to tell by feel whether the vibration is coming from the front or the rear. If in doubt, assume it is the front.

You could try resurfacing the rotors. Or just replace them. Or just buy some hard metalic brake pads and try making a few hard stops, scouring the rotor surface. Or just ignore it and hope it goes away (which it sometimes will do).

xviper

From that link:
After this very short "disclaimer", he procedes to only expound upon the shedding of brake pad material topic. So what does it mean if the rims are NOT installed correctly and NOT tightened uniformly and NOT in the correct order and NOT to the recommended torque specification? Shedding of pad material may indeed be relevent to that particular discussion but it does NOT deal with warpage caused by improper mounting of rims.

Also:
This is the statement that did it for me. It would be illadvised to use DOT 5, silicone based brake fluid in our S2000s. Anyone care to go out and try it and report back to us? In fact, many manufacturers specifically warn against using this type of fluid. In this, Mr. Smith is very remiss.

Although much of the information written in that link is correct, we must also consider that it was written for StopTech as an in-house document. One wonders if some of it is designed to "sell product".