Date: Sat, 10 Sep 2011 09:50:29 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Brake Fade
In-Reply-To: <4e6ac44d.47c2e00a.2390.ffffc044@mx.google.com>
Content-Type: text/plain; charset="US-ASCII"
I fell a bit behind on this tread as I was traveling to Busses By the Buoy.
So here I am in Maine with wonderful weather and friends.
Brake technology has pad materials have changed a lot over the year. The
move away from asbestos and increased demands have changed a lot of things
and brake compalints from noises to vibrations are common for a lot of
vehicles.
Brake fade from overheating pads-discs and brake loss due to vaporized fluid
are two drastically different events. The latter is most noted by the pedal
falling to the floor and usually occurs after the overheating event.
The Vanagon has the be the most sensitive vehicle to proper brake parts I
have ever dealt with. They need a high friction co-efficient such as "FF" or
even "FG" Most long life type such as "EE" just need too much pedal effort.
At minimum the front pads need to be some type of a metallic pad. A good pad
needs to clean, (wear) the rotor to remove oxidation and pad debris.
From experience the factory pads work the best overall but they are pricey
and may not even be available. They also wear hard on the rotors and they
make an awful lot of dust. My next favorite has been the Axxiss "Metal
Masters".
The rears are also extremely important as they contribute much more to
stopping a rear heavy vehicle than many think. I have written a lot about
the rears and there should be stuff in the archives. A problem now is
getting good shoes as VW no longer sell them. The original rear shoes used a
6mm thick metallic lining, riveted, with an "FG" friction rating. So far all
the shoes I am getting are thinner and do not make full contact with the
drum unless the lower shoe mounts are shimmed out. I am looking at some
possibilities to get a better shoe set.
As for break in, yes new brakes need to be seated. Both the pad and rotor
surface need to wear to each other and smot over to get the most friction
possible. New or lathe cut rotors really have lots of voids (that roughness)
so there is a lot of space wear there is not friction. Again the pad has to
be hard enough to cut through this. New rotors are not lathe cut and just
cutting new rotors takes away the benefit of that milled or ground surface
finish pattern that new rotors offer.
For brake noises the most common come from the pads moving in the carriers.
The pad to rotor interface is not linear. The outer part of the rotor
travels much faster than the center. Any variations in the friction
interface added to this will set up oscillations that will vibrate the pads
and make noises. That is why silencing shims or glue are helpful. Brake
grease should be used where the pads have to actually slide on the carriers.
Brake bouncing can be caused by both warped and glazed rotors. Again pad
choice will help eliminate this also.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Edward Maglott
Sent: Friday, September 09, 2011 9:52 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Brake Fade
Thanks for the responses. I have pretty fresh brake fluid and am pretty
sure I didn't boil it. It just really wasn't that hot around the brakes
other than the pads and rotors. I finally got a chance to take the brakes
apart last night and the pads were pretty glazed. I took them to the
college where I work and had the automotive guy look at them. He had a
special pad on an air tool and removed the glaze lickety-split. He also
gave me some stuff to put on the pads and some stuff to put on the rotors
that is supposed to help prevent
glazing. I will note what those chemicals are and report back.
Break-in procedure. There were no break in instructions with the pads. I
found several mentioned on the internet. Tire Rack for example lists
procedures for the Various brands they sell.
http://www.tirerack.com/brakes/tech/techpage.jsp?techid=85
Different ways of putting heat in the brakes and then letting them cool
completely seems to be the theme. When I talked to the auto-tech instructor
he said that like me, he had always heard growing up to just go easy on them
for the first couple hundred miles. But that now, the mfgs in general are
recommending several hard stops then let them cool completely. I'm sure I
can find the box mine came in and maybe figure out what that mfg recommends.
I'm open to suggestions.
Edward
