Friday, April 03, 2020

At Home Maintenance: Bleeding Your Brakes




By: Will Steenrod
Photos By: Julia LaPalme

Now that we’re all cooped up at home, it’s the perfect occasion to spend some time in the garage conducting basic bike maintenance. Bleeding brakes is something often left undone until you can’t stop as quickly as you should. So whether you are on top of your maintenance schedule or this is the first you’re hearing about it, this is a step by step guide bleeding your brakes.


First and foremost, make sure you have the proper tools and supplies for the job. You’ll need:

  • Unopened Brake Fluid: Usually motorcycles need DOT4 or 5.1 brake fluid, but check your owner’s manual or the top of the reservoir for the recommended fluid type. DOT4 and DOT5.1 are interchangeable but NOT DOT5. DOT5 is a silicone based that is only used in specific applications. Another possibility is mineral oil, which will require a special blend recommended by the manufacturer. It’s important to use a fresh unopened bottle of DOT4 or 5.1, since brake fluid will go bad over time as it is exposed to air and absorbs moisture.
  • Bleed Bottle: A bleed bottle is the container that will catch the used brake fluid as you bleed it from your brakes. You can either buy one at the auto parts store, or build one at home out of an empty bottle that’s at least 12 oz. I prefer a sturdy sports drink bottle with a wide mouth cap instead of the thin plastic water bottles that usually tip over easily. A disposable water bottle will work in a pinch if you have nothing else available. Next get about a 2-foot length of clear rubber hose (the clearer the better), and make sure the hose fits tightly over the bleed valve on your brake calipers. Drill a hole just big enough for the hose in the center of the bottle cap. Run the hose through it and tighten a few zip ties around the end of the hose on the inside of the cap to keep it from pulling back out. Finally, screw the cap on the bottle and you have a solid bleed bottle.
  • Tools: This should be obvious, make sure you have the proper tools for opening the brake fluid reservoir, cracking loose the bleed valve, and removing any panels that may be in the way. Most of the time you will just need a screwdriver and a combination wrench.
  • Rags, Gloves, Safety Glasses: Grab plenty of rags. You will need a few to cover potential spill areas and to wipe up any other unexpected drips. Plus it's never a bad idea to have more than you need. Safety equipment is always a good idea. It really sucks getting things in your eye. 
  • Brake Fluid Cleaner: This is a must even for experienced mechanics. Brake fluid is acidic, and will burn spots in paint and plastic. Simply wiping away a splash of brake fluid with a rag won’t get all of the fluid; you need to use a cleaner to make sure you get it all. Brake cleaner works well (as long as it doesn’t damage the surface you’re cleaning) but simple soap (Simple Green, dish soap, etc.) and water work just as well.
  • Assistant Mechanic: Grab a friend or family member that can follow simple instructions. If you don’t have anyone available, just grab a few long zip ties. They’re good at following orders.
Now that you have your supplies let's get to work.

First make sure your bike is on a stable and level surface. If you have a wheel chock or stands, that's great. Take a look at your reservoirs (front and rear) as some bikes may have them mounted at an angle when the bike is upright. You want the reservoir to be as level as possible for this job. This may require the bike to be on its side stand and/or the handlebars turned one way or another. You may also have to adjust the bike's position between working on the front and rear braking systems.

Let’s start with the front brake. Take one of your rags and wrap it around the reservoir just below the cap to catch any splashes or drips. The brake reservoir is located on the right side of the handlebars, next to your front brake lever. Don’t confuse this with your clutch reservoir on the left side, assuming you have a hydraulic clutch. Remove the brake reservoir cap and expansion gasket, and place them on a clean rag. As always make sure that special care is taken with anything with brake fluid on it. We don’t want to damage anything. If your reservoir is low on fluid go ahead and top it off with fresh stuff.


Next locate the brake caliper furthest from the reservoir. If you only have one front caliper that makes it easy, but if you have two then generally the one on the left is further downstream. Check the brake line coming from the reservoir and see which one it goes to first and then second. Start at the second one. If the brake line splits and goes to both calipers equally then start on either one. Find the bleed valve located on or near the top of the caliper. It will normally have a small rubber cap on it. Remove the cap and place the box end of your wrench on the bleed valve nut. Position it on the nut with enough room to open and close the valve repeatedly. Next place the hose from your bleed bottle over the bleed valve nipple. Now you’re ready to start bleeding, the brakes that is.


Grab your assistant and have them operate the brake lever slowly. Have them pump the front brake(s) about three times and then hold. Make sure they do this slowly as some master cylinders will relieve pressure to the reservoir, and without a cap on it will result in a jet of fluid shooting out. If you’re doing this solo and can’t reach the brake lever and the caliper at the same time, you’ll have to do the zip tie method. Once you have pumped the brakes and are holding pressure take a zip tie and tie around the bar and lever. Don’t tie it so tight that you can’t slip it back off. Once you have holding pressure in the system go ahead and crack the valve loose and watch the fluid travel down the clear tube on your bleed bottle. Once it stops, close the valve (normally takes about 1 second). Repeat the pump and hold steps followed by opening and closing the valve until the fluid coming out of the valve is the same color as the new stuff you’re putting in. Make sure you keep an eye on the reservoir and don’t let it run out of fluid. A good rule of thumb is to top it off every third bleed cycle. If you do and it sucks in some air you will need to repeatedly bleed the system until all air is out.


Once the outgoing fluid is the correct color and no bubbles are coming out go ahead and check the fluid level in the reservoir. If it’s too high, continue bleeding until the level is correct. If it's too low fill it to the correct level, close the bleed valve and carefully remove your bleed bottle. Use a rag to clean up any fluid drips and reinstall the nipple cap. If you have two calipers repeat the same steps on the next caliper. Once the caliper(s) have been bled, check if your master cylinder (the part the lever is attached to) has another bleed valve. If so repeat the same bleeding procedure for that valve. If your master cylinder doesn’t have one go ahead and clean off any old fluid on the reservoir cap and gasket and reinstall them. Be careful when placing the cap and gasket back on the reservoir as it may overflow some fluid. If so use a paper towel to wick out excess fluid from the reservoir before replacing the gasket and cap. Once the cap and gasket are on, clean up any residual fluid with the brake cleaner and you are done. Now repeat the same process for the rear brake and you’re all set.


Do you have any tips of your own when bleeding your brakes? Let us know in the comments below

Don’t want to bother with your current brakes at all? Thinking of upgrading your bike? Check out some of our newest listings on cycletrader.com.
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2 comments:

Unknown said...

A motorcycle mechanic once gave me this idea. He said use a turkey baster,but I use an empty saline nasal spray bottle and enlarge the hole to about 1/16". Draw the old fluid out of the master cylinder reservoir first and refill with clean fluid. This way you don't have to draw all the old fluid through the lines.

Robin N Dean said...

There's also the "reverse" (backflush) method, which is far easier ...

https://www.theridingobsession.com/?p=13963