So I've heard of this problem with Hondas where the rotors can sometimes "warp" when hot. I think I have this same problem too. When the rotors are cold, I don't feel any shimmy in the steering wheel, but when I heat them up I can feel it pretty bad. According to an article on stoptech, most rotors don't actually bend, but just develop "sticky" spots. So my guess is that my rotors aren't actually bent, but somehow the sticky spots get stickier when the rotors get warm. Does that sound reasonable? Are OEM brake pads abrasive enough (when cold) to scrub away this sticky spot?
Not "sticky"... more like "softer" or "harder" spots where the metal's grain structure is different. After all, most of the cheap rotors are made in the back of a shack in some third-world country where they melt down old cars, tin cans, broken AK-47s, or whatever they can find. I very much doubt the metal is "pure" anything all the way through, or that they properly cool them after casting to minimize distortion.
A few months back, I ordered some rotors. Right out of the box, I found 5 or 6 ventilation holes right next to each other were still 1/3 full of casting flash that I couldn't chip out, the internal fins were mismatched, like they didn't get the casting molds lined up properly, and the vent slots wobbled, though the friction surface was straight (the only machined area).
The second set were the same, except that on both of these rotors, one surface was already covered with rust.
We changed brands.... clean, dead-straight, fully-machined, perfectly matched cores.
The first set of pads was crap too. One pad had friction material that was twice as thick on the inside edge as the outer, and not *quite* as flat as I'd like... it looked like a wedge-shaped potato chip had been stuck to the backing plate with too much glue, which had squished out around the sides. Real quality stuff.
If your rotors "warp" when hot, but are true when cold, you have a big problem with the metal structure of your rotors. This is the old bimetal spring (like in a thermostat) - means you are running lower quality rotors like MasterBlasters experience. Get some good rotors on the car, and this won't happen anymore.
Alan, You didn't mention what kind of vehicle you're driving, nor the mileage, but if it has ABS, there's a bulletin out there about ABS pulsing at very slow speeds, which can be confused with warping. I couldn't find it in my bookmarks, but I was suspicious that our '95 Odyssey might have the problem too. Get in touch with me, and I'll forward it if I find the link. Do you happen to get an occasional ABS light too?
'Curly'
-------------------------
To REPLY: If there are a couple of underscores in my return address, you must remove them to reply directly . . . . . . Thanks.
Regarding stage performances: When everyone else has finished playing, you should not play any notes you have left over. -
If you are getting an occasional ABS light on a '95 Odyssey, it is much more likely that your ABS system is going south. Have you been religiously changing the brake fluid every 2 years?
I always religiously change my brake fluid. For Japanese cars I recommend that you park them facing East, open the hood, burn incense, strike a gong, and recite a short Shinto prayer before beginning the fluid replacement. Releasing a white dove when the process is complete is essential to a proper fluid change on a Honda. For American cars this entire ceremony can be replaced with shorter ceremony that involves sacrificing a six back of Budwiser and hitting your thumb with a ball peen hammer. For German cars the ceremony is secret and must be performed by the appropriate high priest at the appropriate shrine. As long as you make a large enough offering to the appropriate god, the process will be successful. For British cars the ceremony is best done by covering the vehicle with diesel fuel and lighting it with a match.
Incorrect lug nut torque, as Thomas mentioned, is the most likely cause.
The second thing I'd check is that the calipers aren't sticking, causing the shimmy of slight warping to be magnified. The calipers have to be lubricated with EXACTLY the grease shown in the repair manual. It's pure silicone for my Civic. Generic brake caliper grease will bloat the rubber dampeners on the sliding parts.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.