OwningJames Evans

How to bleed your brakes

OwningJames Evans
How to bleed your brakes

Grab a few tools and save cash by bossing this simple maintenance job yourself. Never done it before? Be confident: you'll feel great getting to know your bike and fixing this issue by yourself

Why bleed my brakes?

Bought a second hand bike and want to upgrade the brakes? Noticing that the bike you've had from new doesn't stop as well as it used to? Stop! Don't spend thousands on a spangly Brembo system just yet: a brake bleeding session can take your bike straight back to brand-spanking-new stopping superpower.

It's a good idea to change your brake fluid each year to keep brake action at its best. Two main types of brake fluid, DOT3 and DOT4, both absorb water. This action degrades the fluid over time, whether you're putting miles on your steed or not.

Tools you actually need!

There's no point starting a brake bleed without all of these tools. Don't own any of them? Go to your local DIY store and get kitted out.
•    Four metres of 6mm or ¼ inch clear plastic pipe
•    8mm spanner with closed ring end
•    Spare empty bottle
•    Clean rags you don't mind being spoiled
•    Brake fluid: 1 litre for front or 500ml back, 1.5 litres for both
•    Kitchen baster
•    Kitchen roll or similar

Use the right brake fluid! Look in your bike’s manual to find what sort your system runs on.

Step 1: Protect your paintwork

Brake fluid goes after paintwork like an Alsatian chasing a rabbit. Wrap a rag around your master cylinder to catch any spills, and cover your tank with another to stop any gloopy air bubble pops. If brake fluid does spill, wipe it up and clean the area with soapy water as soon as you spot it.

Step 2: Remove, clean, and refill brake fluid reservoir

Unscrew the cap covering the brake fluid reservoir and remove any rubber housing that might be protecting the fluid. Now, using the kitchen baster, suck out all the brake fluid languishing in the master cylinder. Mop up any remaining fluid using the kitchen roll, but don't leave any disintegrated kitchen roll in the reservoir.

Old brake fluid that’s absorbed a lot of moisture goes a rich dark brown colour. If your fluid’s dark, then it’s definitely time to flush the system.

Step 3: Bleed nipple to empty bottle

Locate the bleed nipples on each caliper and on the master cylinder and remove any dust caps. You'll need to bleed each one to fully flush the system. Start on the caliper furthest away from the master cylinder. Find it by following the brake lines from the master cylinder. First, slip the ring spanner over the nipple nut, and then press the pipe down over the nipple, checking that it totally covers the nipple and that the fit is tight. Fiddle with the pipe to make sure it doesn't slip off easily. Insert the end of the pipe into the empty bottle to catch ejected fluid.

Remember, start bleeding your brakes from the furthest point away from the master cylinder. On most bikes this is the front left caliper.
Step 4 second pic Caption - Bleeding the rear caliper.JPG

Step 4: Pump and release

Keeping one eye on the reservoir fluid level, pump the brake lever a few times to build up pressure. Then, with the lever pulled in, open the nipple with the spanner. Fluid will start filling the clear pipe and the brake lever should lose its pressure. Close the nipple, then release the brake lever. This action pumps fluid from the reservoir through the system and out of the pipe. Repeat until the brake fluid in the pipe runs clear and without bubbles. Keep the brake fluid reservoir topped up with fluid.

Make sure you keep topping up the reservoir with brake fluid. If you don’t, air will be sucked into the system and you’ll have to start pumping all over again.

Step 5: Don't forget the master cylinder

The master cylinder needs bleeding too. I recently bled my Suzuki GSX-R1000's front brakes. I pumped and pumped, flushed both calipers, but the lever action was still a spongy disgrace. I finished up at the master cylinder bleed nipple. Wow, it was difficult to crack open: the master cylinder had obviously never been bled before! Four quick tugs and the most satisfyingly bubble-filled mess of brake fluid came out through the clear plastic tube. Suffice it to say, the Suzuki's brakes now lift the rear tyre off the floor with ease.

Step 6: Finishing up

After you've closed the bleed nipple for the last time, wrap a rag around it to catch any dribbles, then pull off the tube, emptying any excess fluid into the bottle. Fill the reservoir up to the top marker, replace the rubber seal and lid, and replace any bleed nipple dust caps too. Remove rags, clean up spillages, and you're good to go.

Test your brakes in a controlled environment to check whether they’re working properly before you need them in the real world!

Having trouble?

Still having difficulty with the whole process? Take a look at these points to see whether they sort you out.

  • I've bled and flushed the system, but brakes are still weak! Unbolt your calipers from the discs and check whether your pads need replacing. Is there rust on your discs that isn't wiped off after a ride? Your discs might be misshapen and need replacement. Get them checked out by a pro. Are your bleed nipples at the bottom of your caliper arrangement? Remove calipers from the caliper mounts and hold or tape them so that the bleed nipple is at the highest point. Now the air inside the caliper can escape.
  • Is brake fluid going to dribble everywhere when I disconnect the tube? No, it stays trapped inside the tube at first. Getting all scientific, the cohesion and adhesion of the oil molecules means that it runs slowly through the tube, and needs a strong pressure (gravity, for example) to drip from the end.
  • I've bled the system but my lever is still spongy! Your brake lines might need replacing. As a rule, any brake lines over two years old will be starting to degrade, so replacing them will yield better performance. The rubber starts to bulge with the pressure you're exerting on the lever. If you want rock solid lever action, snap up some braided lines. These are rubber tubes reinforced with metal mesh to keep bulging to a minimum.