Re: Silicone brake fluid

["Richard Klein" <rklein@cris.com>]

On  8 Aug 96 at 11:41, Gary G. Erickson wrote:

> I guess I should clarify my statement.  I ment that it was one of those
> two object (air _or_ water) than DOT 5 didn't like to play with.  I have
> been corrected, that I should have stuck with the statement about DOT
> 3/4 being incompatible with DOT 5 and left it at that! <grin>
> 
> BTW, since we're on the subject of brakes, is anybody familiar with the
> Hawk brake pads?  The guy at my local race shop just loves them.  I've
> ordered a set to try.  (it's _only_ $50  ;-]  )  They sounded good at
> least for aggressive street use and mild track.  Coefficent/Friction of
> .44, no-fade operating range of 100- ~1100 degrees F.  Supposed to be
> extremely rotor-friendly.  We'll see about the dust however!

Rider magazine had an interesting, if not terribly in-depth, article 
on brake pads in the latest issue.  It's about motorcycle brake pads, 
but most of the info is probably applicable to auto applications.  
Correct me if I'm wrong...

Paraphrased from the article:

Brake pads fall into 3 general types:  organic, semi-metallic, and 
sintered metal.

Typically, organic pads are at the lower end of braking performance, 
wear faster than semi-metallic or sintered metal pads, and are easy 
on brake rotors.

Semi-metallics are similar to organic pads but are impregnated with 
bits of metal such as copper or brass.  They tend to provide more 
friction and longer wear than organics, and can be harder on rotors.  
Semi-metallics with the metal distributed more evenly throughout the 
pad should be easier on rotors than pads with the metal present in 
relatively large lumps.

Sintered metal pads work better than the others when cold, are quiet, 
and give good braking power over a wide temperature range.  They are 
somewhat porous, which can help break up a thin layer of water, 
giving better braking performance in the wet.  They have a reputation 
for being hard on rotors, but lubricants can be added (in the 
manufacturing process) to lessen the impact.

I thought they mentioned which type of pad creates the most dust, but 
I can't find it now...

They also point out that a pad that's great on the track may not be 
the best choice on the street.  Racing pads are usually designed to 
create the most friction at high temperatures - temperatures that the 
brakes may never see in street use.  Street oriented pads are 
designed to create adequate friction at lower temperatures.

I've read in several magazines (though not in the fore-mentioned 
article) that DOT 5 brake fluid is extremely hard to bleed all the 
air out of, thus most motorcycle journalists won't use it.  It is 
used in show cars, though, because it doesn't attack paint like DOT 3 
& 4 fluids do.  There is also a DOT 5.1 fluid (though I never see it 
in stores) that is compatible with DOT 3 & 4 fluids, ie not 
silicone-based.  It's distinguishing feature is that it can handle 
higher temperatures than DOT 3 or 4 specs require.

A little knowledge may be a dangerous thing, but I'm happy to share 
what I've got... :)

Corrections and clarifications are invited.

   -Rich

   '85 Audi 5000s   '72 Suzuki GT380
   '85 El Camino SS '73 Suzuki GT550 in pieces

    in beautiful Bay City, Michigan