Sorry John I should have phrased what I said differently.

I'm sure your rotors were warped. I was speaking about what I had
learned on the topic of warpage, (and not the kind I get after some
beers!) and how surprised I was in learning that what might feel like
warping could in fact be material from pads "ground" into rotors
causing pedal and/or steering wheel to vibrate. I had alwasy assumed
(ignorantly)  that warpage was the cause. Either way, my understanding
is that having them turned or if need be replaced, is the solution.

As for beer warpage, I can personally attest to the fact that it is
much preferable to rotor warpage!

Neil.

On 5/17/07, John Rodgers <inua@charter.net> wrote:
> I really can't speak to other vehicles and other
> conditions/circumstances, but those rotor discs on my Van were
> definitely warped. Each time, after my steep downhill grade ride - and
> heavy use of the brakes to prevent excessive speed buildup  - as a
> consequence - the rotors were warped - so much so that further braking
> after getting off the hills made it feel as if the front end was going
> to shake apart when the brake was pressed. Machining the surfaces back
> to true immediately solved the problem. Haven't done that kind of
> driving in a long time now, and the discs have been fine.
>
> Regards.
>
> John Rodgers
> 88 GL Driver
>
> neil wrote:
> > Not that your rotors weren't warped John but.....
> >
> > I was interested to read recently that rotors don't warp as often as
> > one might think or be told by a mechanic.
> >
> > My understanding is that material from the pads can get embedded into
> > metal on rotor. And that it isn't uniformly embedded at that. So when
> > braking, one feels the pad as it rides over the "different" materials
> > on rotor.
> >
> > I'm sure I'll be corrected on these points, but more often than not,
> > rotors don't actually warp. And *some* brake shops are quick to point
> > out that they are, and that they need to be turned or replaced.
> >
> >
> > Neil.
> >
> > On 5/17/07, John Rodgers <inua@charter.net> wrote:
> >> Don,
> >>
> >> Thanks for posting this.
> >>
> >> I have warped front rotors twice due to heat build-up when going down
> >> steep grades. This is good stuff to know.
> >>
> >> Regards,
> >>
> >> John Rodgers
> >> 88 GL Driver
> >>
> >> Don Hanson wrote:
> >> > I learned lots about brakes driving my racecar in road races..
> >> > a few basics..
> >> >   Softer pads work better when cold, but of course, they wear
> >> quicker.  Softer pads are easier on the rotors, but they lose
> >> stopping power as they get hot.  Harder pads don't work so well cold,
> >> but increase their stopping power when they heat up and last longer.
> >> If you keep that in mind, you can select the compound that best suits
> >> your requirements.
> >> >   "Brake fade" is  caused by heat (barring a mechanical failure).
> >> If you have soft pads and use them long and hard till they heat up,
> >> they get less grippy as they get hotter, causing you to push harder
> >> and more often on the pedal to get as much braking force, in turn,
> >> creating even more heat...As the heat builds, it gets transferred
> >> into the brake fluid, and of course, as you put even more force onto
> >> the pedal, you create more heat by further compressing the
> >> hydraulics...As some point, the brake fluid will start to actually
> >> boil, but first, any moisture in your brake fluid will boil, creating
> >> a 'soft pedal'.  Think about 'steam' in your hydraulic system...not
> >> good...  In a race, if you are perceptive, you can feel the brakes
> >> start to "go away" and then your only option is to slow up a bit till
> >> they cool...   ..That is why you want to change brake fluid...to keep
> >> it clear of moisture, which really 'likes' brake fluid.
> >> >    The Brembo brakes on my racing Porsche used to catch fire at
> >> times, being so hot that the rubber 'Gumballs'  picked up in the
> >> suspension off the track would catch fire if we were stopped suddenly
> >> for a crash or something (red flag) .   My hollow core rotors,
> >> perforated also, would last about 2 race weekends before they would
> >> develop heat cracks..My pads would go maybe two weekends also, on the
> >> front..and a whole season on the rear..ATE brake fluid was changed
> >> after every race weekend, sometimes daily..Brakes were the biggest
> >> single lap time improvement on a racecar..
> >> >   If I were driving a WRX powered vanagon, it would certainly have
> >> to have some different brakes than these stockers.
> >> >   What's that have to do with Vanagons?  Not much, unless you have
> >> yours packed full of heavy toys and/or you are towing something down
> >> a long steep winding road...
> >> >
> >> >   Don Hanson
> >> >
> >> >
> >> >
> >>
> >
> >
> > --
> > Neil Nicholson. 1981 Air Cooled Westfalia.
> >
> > http://web.mac.com/tubaneil
> >
> >
>
>
>

--
Neil Nicholson. 1981 Air Cooled Westfalia.

http://web.mac.com/tubaneil