Yet another brake fluid question - dry to wet, how fast?

[dquarasr2]

I've found some graphs that show for DOT-3 'standard' fluid the percentage of water absorption over time but not for specialized fluids like Motul 600 (which is what I use).

I pretty much know the answer to this question already, and I plan to change fluid this Saturday prior to my track day at Homestead on Sunday, but just in case I can't get to it on Saturday, will I be OK on the track? The last time I changed the fluid was for Sebring in mid-April.

Other questions: is absorption and the related degradation of resistance to boiling solely dependent on time, or is use also a factor? This is a very low-use fourth car in our household.

I know that, living in South Florida, where it is very humid (the ambient air usually always has high water vapor content), that I should change the fluid, but I am curious as to just how desperately I need to change it. Like I say, I plan to, but just in case I can't, your comments most welcome.

 

[nsxtasy]

You changed the fluid three months ago. It's fine; don't bother changing it again.

The rule of thumb I use is to make sure the fluid has been changed within the previous 6-9 months before going out on the track. And I use Motul RBF 600 also. I've never boiled it.

A few months ago, I stopped at Acura of Brookfield (suburban Milwaukee) for some service. This particular dealer does a lot of track car prep, including some full-blown race cars as well as many folks doing HPDE events in street cars. (How many dealers do you know that stock Motul RBF 600 fluid, camber kits, and brake applications with two-piece rotors? ) They have the tool that measures the boiling point of brake fluid. I asked their service director how fast the boiling temperature of brake fluid drops over time. He said that, with normal street cars using DOT 3 or DOT 4 fluid, the boiling temperature typically drops around 20 degrees F in a year. With cars being tracked a lot and using high-temp brake fluid like Motul, the boiling temperature can drop as much as 100 degrees F in a year. But that still leaves the boiling point at 493 degrees F, which isn't bad, and it will be even higher if you don't let it go for a full year.

On street cars that don't get tracked, I just follow the advice in the maintenance schedule, and make sure it's changed every 30K miles or 2 years, whichever comes first.