Rear brake barely working

Changed rear tire. When I got it all back together, the rear brake now barely works. Engine braking now has more effect than pushing it down all the way. I bled it, no air. It is in its groove on the swing arm. I pumped it up a good bit. I'm lost.

Are you sure you got the right spacers on the right sides?

One is different than the other if I recall.

Are you sure you got a brake pad on each side of the rotor?

Did you spread pads apart before you put rear wheel back on?

Just thinking of everything going on there.


Removing and replacing rear wheel would not effect the fluid in the line.

My thoughts too. But since It feels very squishy and super weak I tried it anyway.

I think both pads are on there right. Had one come out of the groove once and put it back in. Then we noticed the whole caliper had come out of its groove and had to take everything apart and do it all again :/
Neither spacer is marked, not even with a part number, but I found an old thread where shewolf said long one on sprocket side, so I took it apart to make sure I had done that, and it was. I'm stumped. Once one hand its okish because the rear brake still brakes some but its impossible to lock it up even in a panic stop, on the other hand I'm scared it might one day decide to work fully and get me hurt. I used to couldnt even push down the pedal more than a couple inches, now it goes way down easy.

Here's mine.


Can you remove caliper from bike, remove pads, and compress the piston in with a c-clamp then just push brake pedal and see if piston comes back out?

Your piston is out much further than mine at rest. Hmmm... Mine does push out, just not with as much force as it used to.

I think you are having the same issue as me. except I didn't remove the wheel or anything. Just one morning noticed my rear brake was totally useless.
(I'm guessing though it was a gradual process, I just didn't notice until I lost pretty much 60-70% braking performance from the rear. As you say, it is impossible to lock the rear, no matter how hard you push it down. I only manage to lock it if I'm going at 10 km/h and push it with all my force (and I have got a completely used up rear tyre that doesn't have much grip anyway).

Like you I tried bleeding the rear brake with no results. I also removed the pin on which the pads slide and gave it a good lube with wd40 but still no improvement...

when I change brake pads on some bikes, sometimes the pedal's pressure position isn't the same because I compressed the caliper and it didn't go back to the same place...to increase the braking force, I pry (carefully to not damage the caliper piston) the caliper-side brake pad into the disk while applying the brakes hard, you're trying to let the caliper out more...the reverse of pushing the caliper in to put new pads in...