Wet and Dry boiling points of brake fluid (short explanation)

[svxcess]

Brake fluid is hygroscopic (which means it absorbs water). When fresh from the can, it can be considered "dry" with the higher boiling point. That's why racers and people doing driver's schools change the brake fluid just before events, or at 6 month intervals. Over time brake fluid absorbs water, lowering its boiling point to the "wet" level.

For street cars, wet boiling point numbers are more important than dry because the fluid stays in for quite a while (one to two years). After a few months, with exposure to humid air, and the condensation of water in the system, the brake fluid performance is probably a lot closer to the wet boiling point than the dry boiling point.

[LarryIII]

John,

There is a non-hydroscopic (hydrophobic) brake fluid. I think it is DOT 5, but don't quote me on that.

[Bxsvx]

I think you guys mean hygroscopic

[svxcess]

Originally posted by Bxsvx
I think you guys mean hygroscopic

Thanks, BX, sharp eye! That's what I meant to type. I've since changed it in my posts.


While I was typing this, I was looking out the window and watching the neighbor's dog peeing on the fire hygrant

[Bxsvx]

no problem, the professor in class slammed it into my head, lol

[Mr. Pockets]

Originally posted by svxcess
For street cars, wet boiling point numbers are more important than dry because the fluid stays in for quite a while (one to two years).

That's giving the average person more credit than they probably deserve. I bet few people ever replace their brake fluid.