So what is this "hot rotor warp" thing?

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.

Andrew

 

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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'

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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.

Ed

 

Even Raybestos's premium PG Plus rotors come pre-warped right out of the box.

 

So - you're not going to tell us what the good "brand" is?

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

What kind of wheels do you have, and how were they tightened?

Overtorqued (read impact wrench) alloy wheels can produce this behavior.

Thomas

 

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.

 

Think about it....it'll come to you