You asked for a copy of the brake fluids article. Here it is again,
without all the modifications needed, but better than nothing.
Hope it's not too late...
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Brake Fluids
by Kenneth Streeter,
with input from various sources
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The discussion of whether to use DOT3, DOT4, or DOT5 brake fluids in
Triumphs is a common topic. The information provided herein should
help you to decide which of these brake fluids are best for you and
your car. I would point out that I am not an "expert" on the topic,
but have collected the experiences of many other Triumph enthusiasts,
as well as opinions of professional auto restorers. I have tempered
my findings with my own experiences and opinions.
DOT3
DOT3 brake fluid is the "conventional" brake fluid used in most
vehicles. One of the most familiar brands is "Prestone."
Advantages:
o DOT3 fluid is inexpensive, and available at most gas stations,
department stores, and any auto parts store.
Disadvantages:
o DOT3 fluid eats paint!
o DOT3 fluid absorbs water very readily. As such, once a
container of DOT3 has been opened, it should not be stored
for periods much longer than a week before use.
o Since DOT3 fluid absorbs water, any moisture absorbed by the fluid
can encourage corrosion in the brake lines and cylinders.
DOT4
DOT4 brake fluid is the brake fluid suggested for use in late model
Triumphs. The most familiar brand is "Castrol GT-LMA"
Advantages:
o DOT4 fluid is available at most auto parts stores, and at some (but
not all) gas stations or department stores.
o DOT4 fluid does not absorb water as readily as DOT3 fluid.
Disadvantages:
o DOT4 fluid eats paint!
o DOT4 fluid is generally about 50% more expensive than DOT3 fluid.
o Since DOT4 fluid still absorbs some water, any moisture absorbed by
the fluid can encourage corrosion in the brake lines and cylinders.
DOT5
DOT5 brake fluid is also known as "silicon" brake fluid.
Advantages:
o DOT5 doesn't eat paint.
o DOT5 does not absorb water and may be useful where water absorption
is a problem.
o DOT5 is compatible with all rubber formulations. (See more on this
under disadvantages, below.
Disadvantages:
o DOT5 does NOT mix with DOT3 or DOT4. Most reported problems with DOT5
are probably due to some degree of mixing with other fluid types. The
best way to convert to DOT5 is to totally rebuild the hydraulic
system.
o Reports of DOT5 causing premature failure of rubber brake parts were
more common with early DOT5 formulations. This is thought to be due
to improper addition of swelling agents and has been fixed in recent
formulations.
o Since DOT5 does not absorb water, any moisture in the hydraulic
system will "puddle" in one place. This can cause localized corrosion
in the hydraulics.
o Careful bleeding is required to get all of the air out of the
system. Small bubbles can form in the fluid that will form large
bubbles over time. It may be necessary to do a series of bleeds.
o DOT5 is about twice as expensive as DOT4 fluid. It is also difficult
to find, generally only available at selected auto parts stores.
General Recommendations:
1. If it works for you, use it. You won't hurt anything if you do the
conversion correctly. (generally by replacing all sealing
components in the brake system.)
2. If you have a brake system that doesn't leak or show any other
signs of failure, but has old seals in it, don't change fluid types
as a result of reading this article. If it isn't broken, don't
"fix" it -- you may simply break it instead!
3. DOT3 is an adequate brake fluid for use in Triumphs, although it is
rarely preferred.
4. DOT4 fluid, for a slight increase in cost, will give significantly
increased resistance to moisture absorption, thus decreasing the
likelihood of corrosion compared to DOT3.
5. DOT4 fluid has a higher boiling point than DOT3, making it
preferable for high performance uses such as racing, autocross,
or excessive use of the brakes in mountainous areas.
6. DOT5 is a good choice for the weekend driver/show car. It doesn't absorb
water and it doesn't eat paint. One caveat is that because it doesn't
absorb water, water that gets in the system will tend to collect at low
points. In this scenario, it would actually be promoting corrosion!
7. DOT5 is probably not the thing to use in your race car although it is
rated to stand up to the heat generated during racing conditions. The
reason for this recommendation is the difficult bleeding
mentioned above.
8. Flushing of the brake system every couple years to remove any
absorbed or collected water is probably a good idea to prevent
corrosion.
9. As always, your experiences may vary!
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Kenneth B. Streeter | EMAIL: streeter@sanders.com
Sanders, PTP2-A001 | WWW: http://rassp.sanders.com/streeter/
65 River Road | Voice: (603) 885-9604
Hudson, NH 03051 | Fax: (603) 885-0631
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