Date: Fri, 25 Jun 2010 13:50:41 -0700
Reply-To: Don Hanson <dhanson928@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Don Hanson <dhanson928@GMAIL.COM>
Subject: Re: Brake question......
In-Reply-To: <07f901cb149f$540a2e20$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1
Right on, Scott.
A loaded Westie, maybe an automatic without much engine braking, going
down a long steep grade...that is "Brake Fade...waiting to happen" if you
apply the brake the whole time to control your downhill speed. If you apply
continuous braking all the way down a long hill, the pads and rotors get
real hot and transmit that heat into the caliper and through that to the
fluid. Real hot brake pads are also less effective, requiring more braking
as the heat builds, so you have to push harder, creating even more heat...a
vicious cycle..
The most effective way to descend in a heavy vehicle with small brakes is
to apply them firmly and slow the vehicle below it's 'perfect speed', then
get off the brakes and let it build back up to speed (allowing the brakes to
cool off some) Watch the truckers go downhill.
Brake fade is mostly caused by the moisture in your brake fluid turning to
steam. Brake fluid has a very very high boiling point but it also loves
moisture...So over time your brake fluid will absorb a small amount of
moisture...a drop or two in the whole vehicle's brake system is all it takes
to create a lot of steam....Water expands and creates a lot of steam which
is 'compressable' unlike brake fluid...So at 212f...which is nothing when
you are talking brake temps...your brake system can boil the moisture in old
stale brake fluid and give you the classic "Soft Pedal" of brake
fade....You push and push harder but all you are doing is compressing the
steam that's been created by Hot Brakes...
Changing brake fluid regularly is good. Once you experience Brake
Fade...you will become a believer...if you live.
In my road racing car I changed brake fluid every race weekend, at least.
Sometimes I would change between sessions , if I'd really cooked the
brakes. I use ATE Super Blue and ATE Gold, alternating the two so I can see
when I get Fresh new fluid out of my bleeder valves..Cheap insurance and not
difficult with a Power Bleeder set up.
Don Hanson
On Fri, Jun 25, 2010 at 12:48 PM, Scott Daniel - Turbovans <
scottdaniel@turbovans.com> wrote:
> hi.
> no , that is not classic brake fad.
>
> Brake fad is when you have decent pedal, but brake pads and calipers have
> gotten so hot from continued or hard downhill use, that the brake fluid
> starts to boil...
> then you have essentially no brakes, are barely any.
>
> btw ...
> continued light use ..or steady light use, as in a long decent is not the
> right thing to do at all.
> that just builds up heat.
> Instead...use the brakes hard enough to drop some speed, then don't use
> them ...
> given them some cooling time...then use again a little harder, then let
> cool
> etc...
>
>
> And brake in new pads properly too. Another subject.
> Scott
> www.turbovans.com
>
> ----- Original Message -----
> From: "Paul" <wognacious@GMAIL.COM>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Thursday, June 24, 2010 11:54 PM
> Subject: Brake question......
>
>
> Is this what I've heard described as "brake fade?" I'll be going down a
>> hill
>> and the pedal feels normal, if there is such a thing, and once in a while
>> it
>> feels like the pedal all of a sudden will go right down to the floor
>> board.
>> I
>>
>
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