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The Joy Of New Brake Fluid
By Ren Withnell
Over the years the one thing I've always neglected is brake fluid. It's just a liquid, it hardly moves, it doesn't get dirty like oil, it's not exactly got a hard life just sat there in the reservoir, getting squashed every now and then. I've always known that it sort of reacts with water, even moisture in the air, and that does it not good but once inside the sealed climate of the reservoir there's nothing that can harm it.
I'm learning, the hard way, that this is wrong.
My new to me and now 8 years old CBF 250 has a nice simple 2 pot calliper on one single disc. And the brake felt awful. Wooden, ineffective and the lever was "jerky". When squeezing the lever rather than a smooth action coming back to the bars it juddered it's way in, making progressive and controlled braking troublesome. I of course blamed the lever so removed it, greased the pivot in and the pressure face and replaced it. It was better but by no means cured.
I looked into the sight glass on the master cylinder. The brake fluid looked OK, a bit brown but OK. I'd already stripped and cleaned the calliper but I gave that another cursory check and all seemed well. Stuff it, I rode the bike and tolerated the jerky lever for a while. It's been nagging on my mind for a while though.
I changed the brake fluid. Ooooooh that's better!
Brake fluid is hygroscopic. As I said before it absorbs water and that makes it a bit rubbish for reasons far too dull and scientific for me to learn. It seems even within the sealed confines of the closed hydraulic system of the brake that moisture can crawl in somehow. Opening the master cylinder is an obvious source of contamination. Anyhow it does go off. The recommended life of the fluid is 2 years, I suspect that's the manufacturers being keen to sell more but I think the fluid in the CBF 250 has probably never been changed in it's 8 year life.
If you have any brake issues, the first thing to check is that the mechanisms are free to move as they were designed. Most problems are due to stiff or seized pins, sliders, pistons or levers. After that change the brake fluid. It's cheap, even if it doesn't solve your particular problem then at least you've eliminated a possible issue. Just be careful to keep brake fluid off the bike, anywhere! It eats paint, makes plastic go funny colours and probably isn't good for tyres either.
Reader's Comments
Latchy said :-
I ALWAYS replace brake fluid on any second hand bike I buy I did so on a cg 125 with 69 miles on the clock which was three and a half years old, and only last week did the same again on it. I also gave the front brake an in depth service including a fluid swap on my cbf250 that is 8 years old in April. I have got to say Ren that having rode your machine the other week that the brakes were somewhat lacking compared to my cg125, and that is evidence enough for me that replacing old brake fluid keeps your brakes in optimum condition
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Yeah yeah yeah Latchy. You're the kind of guy that strips an engine down for a laugh too even if there's nothing wrong with it. You're the kind of guy that CLEANS his bike!
Good god man, next you'll be suggesting we should change the oil in the engine every now and then too. For goodness sake.
01/01/2000 00:00:00 UTC
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