Boost your brakes
Flush out old fluid and restore your stopping prowess
1
Feel the need... The need to bleed?
How old is the brake fluid in your bike? It should be replaced every two years, but it’s something that most of us regularly overlook. Fortunately, it’s an easy job. The first and most important thing is to check the type of fluid your bike requires: DOT 4 or DOT 3 are usual. You will also need a basic brake bleed kit – these cost around £12.
2
Get covered not corroded
Brake fluid is bad news for metal and painted surfaces, so you don’t want to spill any on your bike… or yourself, for that matter. Protect the tank and headstock area with a bike cover or old towel. Always have a few sheets of workshop paper at hand ready to mop up any drips that find their way on to unprotected areas. Oh, and stick on some workshop gloves.
3
Pop the cap
Remove the reservoir lid on the front master cylinder; sometimes these are retained by a screw and locating bracket, so make sure this is undone. Remove the lid slowly, making sure the diaphragm inside isn’t going to drop off… Sometimes it will remain in the reservoir, if this is the case gently ease it off and have paper towel to hand to catch any drips.
4
Connect the pipe
Turn your attention to the bleed nipple and then dig out the appropriate-sized ring spanner for it (usually between 8mm-11mm). Remove the grommet protecting the nipple, then place the spanner on the bolt section beneath in a position where you have space to turn it. Next, with the spanner in place, attach the pipe from the bleed kit to the exposed nipple.
5
Crack, pump, tighten…
Using the spanner, crack open the nipple. Whilst doing so, apply positive pressure to the brake lever as if braking gently, then re-tighten the nipple and let go of the lever. Repeat and you should see a clear stream of fluid with no bubbles in the transparent section of the tube.
6
Time to top up
With each pump you’ll see the level inside the reservoir drop as the old fluid is flushed through. It’s important not to let it drop too low, as this will let air in, so keep it topped up with fresh fluid. Pump the fluid through carefully, so as not to risk popping the bleed pipe off.
7
Know when to stop
When you see a change in colour through the transparent pipe, tighten the nipple then check the reservoir level and release the lever. Using a small handful of paper towel, remove the bleed pipe. Repeat the process for the opposite caliper, if your bike has twin discs.
8
Bubbles banished?
With the caliper/s flushed with new fluid, refit the spanner and bleed kit hose to the nipple. Hold the brake lever in and crack the nipple to double check that there are no air bubbles, then re-tighten the nipple. Repeat for both calipers, then top the reservoir up to the max level.
9
Clean the ducts
Before you refit the reservoir cap, turn it over to check that the tiny air ducts within it are free from contamination. These ducts allow air to enter above the diaphragm, which causes the fluid level to drop as the pads wear. Refit the cap with the diaphragm, making sure it is seated correctly, then have a quick visual inspection around the calipers for leaking fluid.
10
Assess the rest of the system
The rear brake fluid can be flushed out and changed in the same way; you’ll often find the rear reservoir just above the back brake lever, or it may be hidden behind a side panel. As a final flourish, check the condition of the other parts of the braking system – the pads, hose routing and any retaining clips and you are ready to go out for a test ride.