Replacing Brake & Clutch Fluid

What is the difference between DOT3 and DOT4 fluid?

 

I don't know anything about all the metallurgy and chemistry stuff they talk up above. But speaking as a person who has put an awful lot of miles on some fairly old bikes, I would change the fluid that often. You would not believe the sludge I have found in the hydraulic systems on my bikes!

In fact, not only should you change the fluid every year, but every other year (at least!) it's good to go through the brake system, disassemble, clean and properly lubricate all the moving parts. And the rubber OEM brake hoses are supposed to be replaced every four years - when the time comes, replace 'em with aftermarket braided steel lines, they cost about the same and they last longer.

Brakes can get really screwed up in a hurry. Especially if you put on 10 or 20 or 30 thousand miles every year and you ride in the rain. I thought this was just because my bikes were old, but then when I bought a brand new bike in 2003, by 2005 the brakes were a every bit as much of a disaster as any other bike I'd owned, and I had to do the same darn things to the new bike as I'd done so many times to my old bikes.

You also need to replace the fluid in a hydraulic clutch, perhaps even more often than the brake fluid. The clutch fluid gets worked a lot harder than the brake fluid, and will discolor faster. If you don't stay on top of it, you'll be missing shifts, and enough missed shifts can cause expensive things to go wrong in the transmission.

One small bottle of brake fluid will do the brakes and clutch on two bikes, and costs about $5. I open a new one every time, and drain the old stuff into last year's bottle along with whatever's leftover from last year. The fluid can take on water starting the minute you break the seal, and I value my time spent replacing it more than I value the dollar I might save by using up the old bottle before cracking open a new one.

After each brake maintenance session I can feel the difference in how my bike brakes. The performance declines so slowly that you don't really notice it, but the improvement when you do the maintenance is very noticeable.