There's nothing wrong with it, it just isn't best for racing. I had it in my
NASCAR TR3, and five or six laps into a race my brakes would get a bit
spongy. Still there, but less precise. I swapped to Dot 4 and they don't. Of
course I need to change the fluid frequently, and any spill lifts paint. I
doubt you'd ever notice this aspect of the compromises in an autocross car.
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Joe Curry
Sent: Wednesday, June 09, 2004 9:57 AM
To: Editorgary@aol.com; fot@autox.team.net
Subject: RE: Brake Fluids
I have seen several people indicate that DOT5 is not good for racing or
autocross. Maybe I am naove, but I have had it in Tiny Tim (The autocross
Spit) ever since I built it in 2000. I have not seen any adverse things
that I would attribute to brake fluid. Maybe I should
change to Castrol LMA for a while and make a comparison. Naaaah! I'll
just leave well enough alone.
Joe
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of Editorgary@aol.com
Sent: Wednesday, June 09, 2004 9:22 AM
To: fot@autox.team.net
Subject: Brake Fluids
In a message dated 6/8/04 6:19:38 PM, owner-fot-digest@autox.team.net
writes:
> Date: Mon, 7 Jun 2004 22:31:14 EDT
> From: GRMTim@aol.com
> Subject: Re: Dot 3, 4, 5 or 5.1
>
> We just did a big article written by a brake engineer on this topic in
the
> July issue of Classic Motorsports. The topic was covered very well.
The
> bottom
> line was to stay away from dot 5
>
> Tim Suddard
> www.classicmotorsports.net
>
There is more to this story than was covered in that article. Noting that
the writer builds brake systems for race cars his perspective may be a
little narrow.
Talk to the curator of any major car museum and you'll find that they use
Dot
5 silicone-based fluid throughout their collections for the same reasons
that it should be considered for the individual hobbyist.
The fluid can be left in a non-driven car for long periods of time in
between uses without any risk of rusting up the pads or clutch disc, it
doesn't have to be changed frequently because it doesn't absorb water as
quickly as non-silicone fluid (note the higher temp rating of silicone fluid
in "wet" condition) and, very important for expensive restorations, it won't
harm expensive paint jobs.
It doesn't give as rapid pedal response as non-silicone fluid because of the
larger bubbles so it certainly wouldn't be desirable for a car that is raced
or autocrossed, but that is its primary limitation.
Two caveats -- silicone and non-silicone fluid can not be mixed because the
combination negates all the additives in both types (and it is VERY
difficult to completely remove all traces of non-silicone fluid from brake
lines), and silicone fluid can break down the old-style natural rubber seals
leading to brake system failure.
But, bottom line -- if you're not racing, and if you've installed a
completely new brake system (all seals replaced with modern materials and
all lines
replaced) in your restoration, you may wish to go the way the museums do and
install silicone fluid in your car.
Cheers,
Gary Anderson
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