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A year or two ago - long before finding this site and starting HM'ing, I had a problem with my brakes causing a-a-n-n-noy-ing vibrations in my steering wheel (together with the whole car).

Instead of rushing to the nearest dealer to get this fixed immediately, I researched the subject, as I was sure that I had not subjected the brakes to extreme temperatures. The problem was revealed as brake pad material imprint on the disks, but I found lots of forums discussing warped rotors/disks.

I even recently read an article in a motoring magazine about an FSP owner trying to get the brakes fixed under warranty, and the dealer accusing him of having warped the disks by driving hot brakes into cold water, and refusing to pay for new rotors.

So here is some links that I found. Information that is very useful to all of us, maybe to avoid being ripped off by dealers, or for promoting DWB and hypermiling. Even though you are not racing or even HM'ing , you might end up in a situation with hot brakes when coming to a complete stop. I have not had this problem again, but I try to avoid a complete stop when approachin a red light downhill, even though I took most of the braking in dfco.

My problem went away eventually. While it lasted, I found I could avoid the vibration (ant potential easier by braking harder rather than lighter, mind you.

http://www.zeckhausen.com/bedding_in_brakes.htm
" If you stop completely and sit for any length of time with your foot
on the brake pedal, you will imprint pad material onto the hot rotors,
which can lead to vibration, uneven braking, and could even ruin the
rotors."

http://www.zeckhausen.com/avoiding_brake_judder.htm
" After a fast lap on the race track or a high speed stop from over
120 mph, your brake rotors may be literally glowing red hot. If you
keep your foot planted firmly on the brake pedal after coming to a
complete stop, you may find your brake pads bonded firmly to the
rotors. The extreme heat melts the surface of the pads and forms an
imprint on the rotors. This imprint is a few ten thousandths of an
inch thick and can result in a noticeable shimmy. If it happens on
unbedded rotors, you will also end up with a significant difference in
the coefficient of friction between the imprint and the rest of the
rotor, further aggravating the situation."

" After the track event is over, you should not switch back to street
pads right away. Instead, drive home from the event using your race
pads. As they cool down, the race pads will once again go into pure
abrasive mode and polish away their own transfer layer from your race
weekend. Cold race pads will even cure judder problems from pad
deposits accumulated during the track event. By the time you get
home, the rotors are polished clean and ready for you to install and
bed your street pads."


http://www.stoptech.com/tech_info/wp_bedintheory.shtml
As stated above, the objective of the bed-in process is to deposit an
even layer of brake pad material, or transfer layer , on the rubbing
surface of the rotor disc. Note the emphasis on the word even, as
uneven pad deposits on the rotor face are the number one, and almost
exclusive cause of brake judder or vibration.

Let's say that again, just so there is no misunderstanding. Uneven pad
deposits on the rotor face are the number one, and almost exclusive
cause of brake judder or vibration.

It only takes a small amount of thickness variation, or TV, in the
transfer layer (we're only talking a few ten thousandths of an inch
here) to initiate brake vibration. While the impact of an uneven
transfer layer is almost imperceptible at first, as the pad starts
riding the high and low spots, more and more TV will be naturally
generated until the vibration is much more evident. With prolonged
exposure, the high spots can become hot spots and can actually change
the metallurgy of the rotor in those areas, creating "hard" spots in
the rotor face that are virtually impossible to remove.

Sounds completely reasonable. When teaching Prius drivers the
"neutral trick" for cleaning off their rusty, underutilized
rotors and drums I emphasize the importance of doing a long,
EVEN-pressured braking event and not coming to a stop while
doing it. Stabbing the pedal and doing the "lurch" at stops
just seems like a recipe for poor performance and more rapid
and uneven degredation -- I had an old girlfriend who I'm
convinced killed the brakes prematurely on her then-new Civic 15
years ago because she'd wait until the very last moment and then
hard-brake up to lights and let the car do the "rebound" after
stopping. And of course keep the brake foot down with the
auto-slushbox still in "D" and sitting there dragging on the
torque converter to generate and waste even more heat. Even
after cupping her rotors into useless scrap back then and maybe
a few more times thereafter, for all I know she still drives that
way despite several educational attempts.
.
I always feather OFF the brakes when arriving at the final stop,
and pop into "N" both in my Prius and any other auto trans I
have occasion to drive, avoiding the lurch and the standstill
stress. Sometimes it involves looking out the side window to
determine ground speed and the right point to let up. The
additional subtlety in the Prius is to try and stretch the regen
event as long and as even as possible, keeping charge current under
50 amps when doable. Usually I can confidently get out of the car
and stick my finger right onto a brake rotor and it's stone cold,
even with the little bit of physical braking down from 7 mph.
.
_H*

Usually when people talk about "warped" rotors they are referring to a condition that shows up on a dial indicator as "runout" that looks like a small amount of warp and is indicative of uneven wear of the rotors. My understanding is that this condition can be caused by a number of different factors. Mis-tightening of the lug nuts by poorly trained or careless technicians is often cited as the most common root cause. That is what appears to have happened the last time we bought new tires for our Saturn.

I'm not saying the uneven pad deposition theory is necessarily wrong, but rather is contrary to conventional wisdom. It's a hard theory to prove or disprove as a first cause because it is also easy to see how uneven deposition would be a consequence rather than a root cause of rotor warp/uneven wear.

The glazing was visibly uneven on the warped rotors I replaced on our Saturn. Next time I have to fix warped rotors I'll examine their glazing more closely in addition to checking my lug nut torques.

Ask Volvo how many sets of front rotors they replaced under warranty
on my car from 1987-1990 ?
They finally upgraded the front rotors to 11.25 inch diameter from
the original 10.25 inch. I have had no more problems with rotors warping.