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Hi everyone
So my rear brake rotor bends outwards (away from the hub) when I apply my back brake (Zee brakes). It’s making the brake feel underpowered and unpredictable.
I’ve checked the rotor is true, and it is. I’ve tried loosening off the calliper, applying brakes and re-tightening. I’ve tried this with and without the dome shaped washers to see if it made a difference. It seems that when I tighten the calliper back up it gets pulled out away from the hub.
If the chainstay mount wasn’t flat I assumed the dome shaped washers would remedy this problem, but they don’t.
All pistons appear to be moving freely.
Any ideas?
I have tried lbs, they said brakes needed bleeding, which they did, but the problem persists...
Hoping Someone here may have something memisdom to share, thanks.
Have you tried simply setting the calliper by hand/eye you ensure the rotor is central when all tightened up?
This Hope video describes what you are experiencing and how to set calipers up. Yes it's aimed at Hope brakes but the principles will be the same for other makes.
I assume you checked all rotor bolts in place.
Might need to make the caliper and or the adaptor holes a bit bigger with a file.
Is the hose really tight ? It might be pulling the caliper.
Has it always been like this or is this a recent development on a bike you've had a while? What type of axle? Have you changed the wheel/hub recently? Is the axle fully located in the frame?
ps - I'm surprised it's making the brake feel underpowered and unpredictable. What are your pads like and are they wearing evenly?
The rotor is not centralised - follow the hope video = this is the proper way of centralising callipers. My bet is a stuck piston
do NOT take a file to anything. check both pistons are moving equally , push them right back and then centralise the calliper by eye.
Bike shop is bang out of order - thats never a bleeding issue.
Thanks for all the responses!
yes, I’ve tried re-setting by hand/eye. Made no difference as it just pulls out of position again.
All rotor bolts are in place and the hose isn’t too tight in my opinion.
The brakes were taken off an old bike and fitted to a new build (Whyte 909 originally and put on a Bird Zero) but worked fine at first.
Axle is 10mm bolt through and tightened properly.
Ill have a look at that Hope video and see if that helps. It may be the pistons aren’t moving freely and my untrained eye isn’t spotting it.
I wasn’t happy with the shop either, Felt fobbed off but never mind.
If the pistons are the problem is that easily sorted?
Thanks again for all the responses, gives me a few things to try out.
One might be sticking because of dirt - might be worth applying a little light lube to the sides of the piston. Again there are videos available. Again here's a Hope one -
Awesome, I’ll give that a go. Thanks again
Sounds like pistons on one side are sticking a little.
Take the wheel off and pads out and look at how much the left pistons sit vs the right pistons. Then give the lever a careful squeeze and watch how they move - careful not to squeeze too much which might pop piston(s) out but one solid squeeze should be OK. If left & right sets sit unevenly and/or one side moves more than the other when the lever is squeezed then you need to free them up.
Simply pumping the lever, pushing pistons back in and repeating is sometimes enough. You can isolate the front or back pistons by blocking the other ones with a Shimano yellow bleed block. To isolate a single one you need to use the bleed block on one pair and a plastic tyre lever on one other one - squeeze very carefully when isolating one piston! Using mineral oil to lubricate is potentially bad for the seals so I use Castol red rubber grease as a lube when they need it.
I do this every other time I change my pads and it makes a big difference.