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[ANSWERED] Brake fluid and track events

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[ANSWERED] Brake fluid and track events

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Old 10-27-2017, 02:17 PM
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jvp
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Default [ANSWERED] Brake fluid and track events

The original question is here.

koranke asked:
The owners manual states that, for track events, the factory brake fluid needs to be replaced with qualified high performance brake fluid with a dry boiling point greater than 279 Celsius. It also states that one should replace the track brake fluid with factory brake fluid before driving on public roads. Why is this? I read a blog post from someone suggesting that high performance brake fluid absorbs moisture quicker and consequently can lead to increased corrosion in the braking system compared to regular brake fluid, but I've also seen posts from others who use high performance brake fluid for all driving and don't report any issues. What bad things could happen from using high performance brake fluid for daily driving on public roads? Or, is the issue really that any brake fluid, once subjected to a day on the track, needs to be changed as soon as possible, and that there's nothing wrong with using high-performance brake fluid on the street?
Tadge answered:
Koranke, your question raises the exact considerations we take into account when making brake fluid recommendations. Placing customer safety as our highest priority, we advise people to replace the brake fluid after a track event and to revert to street fluid for use on the street. Customers vary tremendously in how hard they use brakes... And it is not necessarily correlated to their lap times. Our professional endurance race car drivers are actually relatively easy on brakes. Some customers are very hard on brakes and end up putting lots of heat into the pads, calipers and fluid. When brake fluid boils or comes near the boiling point, it makes it more likely to boil on the next brake application. Since there is no sure-fire way to assess the condition of the fluid after a track event, we have to recommend replacement as the safest possible alternative.

Your question mentions water absorption. While counterintuitive at first, a small amount of water absorption is actually desirable. The water helps activate the corrosion inhibitors in the brake fluids that help keep brake system components chemically stable. And, just like with antifreeze, these inhibitors are gradually depleted in use, which is the primary reason brake fluid needs to be changed. DOT 3/4 glycol-based fluids will absorb water at different rates and, of course, more than a trace of water starts to be a bad thing. Race fluids, by their nature, generally absorb water more quickly than street brake fluids which can dramatically reduce their boiling point, potentially below that of our factory fluid. This reduction can lead to risk of boiling fluid at lower brake energy. So, again with safety in mind, we recommend going back to street fluid for street driving to avoid the water uptake more likely in race fluids.
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Old 10-29-2017, 10:54 AM
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JerryU
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Originally Posted by jvp View Post
The original question is here.
Excellent response. Answers the question I had about hygroscopicity of racing brake fluid!

Dot 4 "standard" brake fluid is said by some reputable sources ( http://torquebrakefluid.com/abc.html ) to be somewhat less susceptible to water absorption. However racing brake fluid is said to be worse and many are DOT 4! Obviously, however racing fluids are formulated to have higher dry and wet boiling points can make them more hydroscopic!

That is not data provided by the brake fluid manufacturers. Hygroscopicity varies in that regard and is NOT a parameter in the DOT 4 spec.

Last edited by JerryU; 10-29-2017 at 11:23 AM.
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Old 10-30-2017, 10:08 AM
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The impact of tires - my last track day I was out for the first time on Nitto NT01 (on my C5) and when I got back in I put my hand on the reservior and it was hot!
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Old 10-30-2017, 11:54 AM
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Originally Posted by JerryU View Post

Hygroscopicity varies in that regard and is NOT a parameter in the DOT 4 spec.
Key Point there.
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Old 10-30-2017, 11:06 PM
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Just run RBF600 and bleed a bottle out before each track day. It'll be more than fine.
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Old 10-31-2017, 01:21 PM
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The color alone of brake fluid is a good indicator of when it's time to be changed. You can run a track event, and be kind to the brakes, and continue to use the brake fluid in the reservoir on the street or at the next track event, or you can be hard on the brakes, and need to change it in the middle of your event. Many variables to consider. It's just good overall practice to change your brake fluid before every event. Brakes are one of the most important safety items on a car, why screw around?
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