Tried my first ever bleeding on Shimano Ultegra rear brakes, after my son touched the brake lever while bike was on the trainer and got air in.
I tried the easy method first as per Cycling Weekly guide https://youtu.be/TYhb8tGUzbs?si=PMrk7WGfAlClGeSN but despite putting the bike upright and getting out heaps of air bubbles it just didn’t work – I was optimistic as no more air was coming out and the lever wasn’t as spongy as the start, but no luck with braking.
Need to do the proper full bleeding tomorrow.
Being the rear brake, so a longer hose, does anyone have any suggestions on how much mineral oil I need to add to the syringe?
by Lucas77Oz
9 Comments
If you push the lever with the wheel out, usually you just need to retract the pistons. did the piston get ejected or something?
did the pistons fall out or something? i dont think that should have happened, usually when that happens i just push the pads back with a tyre lever. also i usually do as much as i can for rear, about 25 ml and about 10-15 ml for the front, better to have too much than not enough
Just push oil from the calliper to the lever until the bubbles stop. No measurements needed.
Did the pistons eject when the lever was pulled? If that is the case you will unfortunately have to replace it. Rebuilding Shimano pistons is not possible.
A trick I use is to press the lever in slowly then release quickly.
You can do this on a full bleed or burping.
About the video.
When full bleeding I undo the nipple then put the syringe kit on the nipple to minimise air and know the nipple is undone enough to let fluid through when the nipple leaks.
Then I undo the bleed bolt on the lever and add the funnel, then push the syringe on the caliper side.
Pulling the lever while the bike is on a trainer without pads or a rotor doesn’t let air into the system, it only moves the pistons inward and you just have to push them back to get the rotor in again.
Just for thought – not saying this is the right or only way:
I keep the bike less upright, push not pull the mineral oil, and make sure to move the handle bars around during the process to get all the air pockets out (especially from the brake’s reservoir). I used to pull the oil instead of pushing it and that was a major mistake.
You can’t introduce air by pressing the brake lever without the wheel in place. If you got air in your system it came from somewhere else
Cup at the lever end,and a 3/4 filled syringe at the caliper end and pump fluid through until there are no more bubbles. Repeat the cycle if the oil comes out black but always leave one end plugged in so oil doesnt drip out. Takes 5mins to 10mins
++Don’t forget to push the pistons back fully before starting
Bike is done, throw it in the bin and get a new one.