May - June 1997 Motor State Performance Report Article By Jim Kaekel, Jr.
Often taken for granted, brake fluid is an important ingredient in the preparation of today's competitive circle track race cars.
Here's the real red "meat" of your tech tip: Only glycol-based racing brake fluids should be used because of their higher temperature rating.
Brakes get extremely hot under racing conditions, causing anything but the BEST fluid to boil and, in turn, leading to a "spongy" pedal, or even a complete loss of braking power!
When selecting an appropriate brake fluid, take into consideration both the wet and dry boiling points specified by the United States Department of Transportation (DOT).
In racing situations, a fluid that meets or exceeds the DOT 3 standard would be the type used.
The DRY boiling point of a brake fluid is measured when the fluid is completely free of any moisture contamination.
The WET boiling point refers to fluid that has absorbed moisture, which can significantly reduce the minimum boiling point of the fluid.
The DOT 3 requirement for web boiling point is 284 degrees Fahrenheit while the DOT 4 minimum is 311 degrees Fahrenheit.
By way of contrast, consider that the dry boiling point for DOT 3 fluid is 572 degrees Fahrenheit.
There are several brands of brake fluid that exceed these specifications: Sierra (#012-14640), Performance Friction (#90016), Allstar (#78108) and Wilwood (290-0632).
All offer fluid with a minimum dry boiling point of 570 degrees Fahrenheit. In addition, Wilwood's fluid utilizes a low viscosity formula which eases the process of brake bleeding, and also reduces foaming under the heavy "pedal pumping" conditions which exist in circle track racing.
While silicone based fluids are DOT 5 rated, they have both distinct advantages AND disadvantages. Two advantages are that silicone fluid has a very high boiling point and will not absorb moisture from the atmosphere like glycol-based fluid.
However, silicone should never be used in a circle track race car because its higher viscosity can cause the calipers to "drag". Silicone fluids EXPAND in high temperature situations, creating more compressability and causing a very "spongy" brake pedal.
Some manufacturers have also found in testing that silicone fluids contain properties which can cause the seals to swell.
Because brake fluids which are glycol-based absorb moisture quickly, it is imperative that the fluid in the system always be kept fresh to avoid problems.
Also, keep the master cylinder reservoir cover on at ALL times, except when servicing. Keep fluid containers tightly sealed when not in use and never re-use any fluid after it has been bled from the system.
It's a good idea to periodically flush the system just to keep the brake fluid optimally fresh. Anytime you experience severe brake fluid temperatures, flush the system as soon as possible.
Be careful of pressure bleeders that store fluid, as the fluid contained there is exposed to air and moisture and will quickly deteriorate.
A brake bleeding kit, such as a Tilton #72-503 (pictured) would be helpful at this point. It includes two bottles, hoses and complete instructions.
If you are suspicious of a problem possibly related to high brake fluid temperatures, you can purchase another helpful product manufactured by Tilton called a Tempilaq Kit (#83-200-6).
This kit includes a special paint, available in five different colors and temperature ranges. The Tempilaq can be applied to the brake calipers or pads and when the specified part reaches a given temperature, the paint's original color will disappear. The outside of the caliper should not be allowed to exceed 500 degrees Fahrenheit.
The chart shown, courtesy of Stewart Brake Systems, offers suggested plumbing for several styles of braking systems.
If you have any questions, please feel free to call us. Our team consists of racers, rodders and engine builders (we believe you can't sell it, unless you know how to use it!). Our sales/service folk will be more than glad to help you out.
By choosing the appropriate plumbing and quality brake fluid (and always keeping your brake fluid fresh and free from moisture), you are much less likely to run into problems like boiling brake fluid.
After all, if your brake fluid boils - causing your brakes to fail - and you take a nice turn into the wall, your blood may also begin to boil (as you contemplate some much costlier expenses).
You know the old adage "An ounce of prevention is worth a pound of cure."
Or remember the golden Oldie from Neil Sedaka, "Breaking (Braking) Up Is Hard To Do..."