Fluid levels
Do we really pay as much attention to what our brake fluid is doing as we should? Listen up, says Ralph Ferrand!
Words and pics:
Many bikers who look after their own steeds change the oil and filter, the spark plugs, check the disc pads and check that the lights work. Very few seem to have a clue in a bucket how often other fluids need changing, nor the brake lines. Standard stock rubber brake lines should be changed every four years: fact! Given the huge cost of stock items a sensible person will replace the cheap (to make) OE rubber lines with braided lines with stainless fittings. They are less costly than OE and many, such as HEL, carry a lifetime warranty. Rubber lines swell under pressure, wasting lever/pedal effort which should be going into stopping the bike. If you lightly grip a rubber brake line, especially an old one, and grab a handful of anchor you will feel the line expand slightly in your fingers. The power to swell that line should be acting on the brake pads! Another issue that few seem to appreciate is that brake fluid has a fairly short lifespan and should be changed regularly. It is hygroscopic, which means that it absorbs water. On the whole this is a good thing as it stops the water collecting in corners of the braking system, but you don’t want a very high concentration of water as it will attack the braking system components. Watery fluid often sets up corrosion behind the caliper seals and the flaky aluminium pushes the seal tight against the piston, massively reducing brake efficiency. The water also attacks the chrome of the piston, eventually holing it and setting up rust underneath in the mild steel. For some bikes it is just the hassle and expense of new pistons, for others you really have a much bigger problem if you can’t get a new one. At its worst the water loaded fluid will boil in the calipers from the heat generated from the pad to disc friction and that is really bad news. Laser Tools produces a cracking little professional tool for the trade which measures the water content of the fluid. We bought one years ago and have found it invaluable. We not only test the fluid in the bikes but also the new fluid.