Reed asks: “I’ve seen your video on bleeding brakes without a proper bleed kit, but because Shimano brakes can be finicky, can you show me how to do a full and proper Shimano brake bleed?”
Shimano brakes are some of the most durable, dependable, and bomb proof brakes on the market. Whether air has entered the system or the fluid is dirty, they’ll eventually need a bleed. Luckily, it’s a relatively quick and painless process. Shimano brakes can be bled on the bike, but removing the system and keeping the caliper lower than the lever at all times will yield better results.
Start by removing the wheel from the end that you’re planning on bleeding. Remove the pads from the caliper, then insert a bleed block into the caliper. If you don’t have a bleed block, a stack of business cards, an appropriately sized piece of wood, or any variety of flat and hard objects will suffice.
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Next, remove the bleed screw that sits atop the lever’s brake reservoir and screw the oil funnel into the reservoir. Before the next step, mark the position of your lever before so you can get the lever back to its original position after the bleed. Now, rotate the lever on the bar so it’s parallel to the ground. Put a 7mm wrench over the bleed port screw on the caliper using the closed end of the wrench. Now fill the syringe with oil (only want 50ml of oil?) and attach it to the bleed port on the caliper.
With the hose attached, open the bleed port by loosening the bolt and start pushing fluid from the caliper up to the lever. The fluid should move through the line relatively easily. If this seems difficult or you are feeling resistance, open up the bleed port a little more. Continue to push fluid through the line and into the funnel on the lever until you no longer see air bubbles coming out. If you notice the fluid coming into the funnel is discolored, you may have to repeat this process a few times until the dirty fluid has been displaced by new mineral oil. Once you are no longer seeing air bubbles or dirty fluid, you can close the bleed port on the caliper, but don’t start pumping the lever yet.
Next, remove the syringe from the hose at the caliper, and put a bag over the hose end to catch any fluid. Reinstall the caliper’s bleed nipple. After that is set in place open the bleed port once again and simply wait for fluid to start draining from the caliper. Be sure to pay attention to the fluid level in the funnel and make sure you add fluid as is necessary to keep air from getting into the system. Once there is no air coming out of the caliper, you can once again close the bleed port.
Now, squeeze the lever to the bar and hold it down. Open and close the bleed port in rapid succession. Repeat this process 2-3 times and then close the bleed port. Pump the lever a few times to remove any remaining air that may have been trapped. The lever should pump up and get firm. Once the lever feel is firm, insert the plug into the funnel and remove it. Re-insert the bleed screw, wipe away any excess oil on both the lever and caliper and you’re good to go. Don’t forget to put your levers back into the proper position, as was marked by the tape you installed earlier. All that’s left now is to put the pads back in the caliper and hit the trail. For all your braking needs, check out ArtsCyclery.com