Silicone Brake Fluid vs Conventional Brake Fluid

[TBM Brakes]

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Silicone Brake Fluid vs. Conventional Brake Fluid
An interesting topic of discussion around the race tracks is the debate over silicone brake fluid versus the more conventional polyglycol (a.k.a. DOT 3,4 & 5) fluid. What follows is some factual data relevant to the silicone brake fluid debate for you to make up your own mind.


DOT What?
A hydraulic brake system must have brake fluid in order to function properly. The level at which the brake system does operate is dependent on the choice of fluid. Among other things, the more important elements of brake fluid are high boiling points, consistent viscosity, and good lubricating ability. All brake fluids commonly used in automobiles sold in the United States, are regulated by the department of transportation (DOT). The container will have a number such as DOT 3, which refers to the DOT test designation that the fluid meets. The number designation does not imply a rating for comparison between the fluids, only the number of the test!


More.................http://www.tbmbrakes.com/silicone_brake_fluid_vs__conventional_brake_fluid


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[Skip Fix]

I think if silicone has as many disadvantages as listed it would not be fluid of choice for military spec vehicles that I would guarantee work under more varied temp ranges than any of our cars do(think Iraqi deserts to Alaskan tundra temps), nor the choice for several motorcycle companies OEM fluid.

My '78 TA has had it in since 1985 when I added the '81 TA rear disc setup. It has been autocrossed for years road race slicks/CP before becoming a street/strip car the past 15 and has never experienced a change in pedal feel, even making a hard stop for the first turn around at the strip fomr 125mph. Never leaked a drop or blown a seal. I can't tell you how a NASCAR or all out road course car would do with it but my system has been pushed hard for years and performs well.

Most new/rebuilt calipers, MCs I have seen the past decade have silcione on the seals from the feel and not a glycol base.

Like in the medical field you need to do a "double blind study" -same car same system same driver different fluids neither he nor the mechanic know which one is which(bar codes only on the bottles) and see how the performance is. I think much data is still carried over from the 70s when brake systems and fluids were much different than current. Those objective impressions are now "hard data".

[Nicks67GTO]

I kind of wondered about this^^^ I had it in my GTO's 11" TRSD brake kit for a few years and it worked fine. I'm now changing to a C6Z51 kit so i'm flushing the lines and putting DOT4 in just simply because that's what was recommended.

You see a lot of bad press on here about DOT5 but has anyone ever actually had a failure or issue with it? Or is this all just hype and theory?

[TBM Brakes]

I don’t see that the article bashes Dot 5, it certainly has its place. It is not corrosive to paint, it has a higher boiling point than conventional Dot 3 or Dot 4, and it is not hygroscopic, all of these are advantages to Dot 5. What the article states is that it also has some deficiencies; it has higher compressibility and that compressibility changes with temperature. Dot 5 is also more expensive than most of the Dot 3, 4 and 5.1 fluids.

To quote the last paragraph of the article:

“In essence, although both types of fluids have advantages and disadvantages, the bottom line is that the disadvantages of silicone brake fluid render it unacceptable as a safe and reliable alternative to polyglycol fluids under all conditions. It has no place in any race car! On the other hand, although DOT 3, 4 and 5.1 fluids have problems, these problems are controllable given reasonable care and maintenance.

Consistent even pedal travel is extremely important to safe stopping distances. It is even more important to giving a race car a consistent, repeatable feel to the pedal, so the driver knows he can depend on maximum performance.”


Peak operating temperatures and duration at temperature play a large role in brake fluid selection, whether it is Dot 3,4,5 or 5.1, what the linked article sets out to do is provide concise information on the differences between the various fluids and give a recommendation for use based on our experience.

[Skip Fix]

Consistent even pedal travel is extremely important to safe stopping distances. It is even more important to giving a race car a consistent, repeatable feel to the pedal, so the driver knows he can depend on maximum performance.”

That is where I disagree it is a "real" problem", having personal experieince with it on a raced car. Lots of things in life, engineering and medicine have the potential for a theoretical problem that in real world use never happens.

I think some of the potential may be from the viscosity it is thicker and could hold air bubbles easier. Gte sloppy about pouring it in the MC, poor bleeding and you have some small air bubbles that allow compressability. There are several classic British sports car sites that go into this same discussion and come out some of the negative are not real issues in the car.

From SSBC: http://www.jegs.com/InstallationInstructions/800/884/884-A1103.pdf

[kevmurray]

Hi -what is your name? :)

Thanks for posting, its nice when industry experts come on here and share knowledge for free. I was concerned about the expansion locking the brakes. Did the return ports in the master cylinder get blocked? Was there no reservoir for expanding fluid?

While not the same cause, I once had a single front caliper lock up (from corrosion in the piston bore). It was not fun!