Date: Thu, 17 May 2007 09:40:36 -0700
Reply-To: neil <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil <musomuso@GMAIL.COM>
Subject: Re: Brakes...no van content.
In-Reply-To: <464C2748.5050603@charter.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
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
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