So what color is the brake fluid?

[Lorien]

This came up on the ST forum not so long ago and I will repeat it here because I was looking at the fluid in both the window on the handlebar and the resevoir under the seat as a matter of course. Have never seen the brake fluid any color than a light yellow. So I ask again what color should it be? I remember that my ST had different color fluids in the brake and clutch windows from day one and no one could ever explain that since they were supposed to be the same.

 

[elizilla]

The brake fluid, fresh from the bottle, is clear. The instant it absorbs any water vapor it starts yellowing. It should be changed when it gets about as dark as a light-to-average beer. If it's as dark as dark beer it's overdue.

The NT has a cable clutch so we don't have to worry about the clutch fluid. But my experience of hydraulic clutches is that the fluid darkens faster, and on some bikes the clutch fluid also picks up contaminates other than water, that add a black overtone to the mix. So it will turn greyish instead of brown. I think this is because the clutch fluid moves a lot more volume, a lot more frequently, and there's a lot more travel on the piston in the slave cylinder, so there's more chance for grime to get in past the seals.

 

[charlie b]

Different applications. Brake fluid is an extreme high temp hydraulic fluid. Clutch is not.

 

[elizilla]

Yeah, so even though the clutch fluid gets more stuff in it more quickly, there is less heat so it's less likely to boil and get gas bubbles because of it. Not that it won't eventually do that too. But you can get away with changing it on the same schedule as the brake fluid, even though it's nastier by then, because there's a bit less heat.