Rear Disc brake stuck on

Mart79

Active Member
Hi guys
Was experimenting with my bike earlier, basically seeing what it would look like with slimmer tyres on it. (I currently have 27.5x2.8) Whilst I had the wheels in the air, I noticed the rear wheel doesn't roll free. As soon as you stop rotating it by hand the wheel stops dead. Looking at the calliper and pads you can see day light in-between 1 side of the disc and pad, but looks as though the pad on the inner of the disc is right up against the disc effectively slowing the wheel down.

I undid the screw on the calliper a turn at a time which I can only assume is an adjuster with each turn the rotation got slightly better but only very slightly better, however the more I undid the screw I started getting a nasty rattle, like the pads were too far apart and they were vibrating and was quite loud.

Is it best getting it back to Halfords where I bought it and get them to sort it or is it a quick and simple fix
 

Drago

Flouncing Nobber
Location
Poshshire
They likely need centreing.

Slacken off the caliper mounts so the caliper is still in place, but loose and free to move.

Get a chum to hold the brake firmly on while you tighten up the bolts progressively, a little bit of each bolt at a time.

Release the brake and check again. You may and that one piston does not quite move at the same rate as thenother, and there's not much you can do about it. Some very light brushing of the disc as it goes round isn't a problem.

Bear in mind that some systems, typically mechanical discs jobs, may have only one moving piston and the opposite padmis fixed and relies on the disc deforming fractionally as the brakes are applied. You can usually adjust the inner pad via a hex key adjuster on the rear of the caliper.
 

T4tomo

Guru
Before you centre the caliper, put the bike on the ground, undo the quick release on the wheel and make sure it’s centred properly.
And when you re insert a wheel after you have centred per @Drago above, apply the brake before you do the last bit of tightening of the QR skewer, whilst applying a little bit of weight to the cross bar / saddle / bars to ensure it seats back centrally again. and do your skewers up tight, it should leave a bit of a print on your palm as you close it.

if you have thru axles then this is less of an issue.
 
Is it best getting it back to Halfords
It is rarely best taking a bike to Halfords!!!

Are these cable or hydraulic disc brakes? Could be wheel positioning as mentioned above or maybe you have squeezed the lever with a wheel out if hydraulic?

If they were working ok before you had the wheel out then I wouldn't suggest trying to 'centre' them now until you find out what has changed.
 
OP
M

Mart79

Active Member
I didn't remove the rear wheel, just the front as it was the easiest to take off.

the brakes are cable disc brakes. it looks like the wheel is off centre ever so slightly. possibly as simple as the quick release has worked it self loose, I had a problem with the front wheel jerking to the left when applying the brakes, that turned out to be a loose quick release.
 
As @T4tomo mentions above, Quick realise and disc brakes are a pain in the arris. Probably when the oinks in the shop inserted the wheel they weren't aware that when you close the QR, the very last bit often shifts the hub a smidge to one side or the other. With the close tolerances of disc pads, this can result in one pad rubbing the disc.

My trick is the hold the wheel and one part of the frame and eyeball the clearances in the back of the caliper, then as I'm doing up the QR lever I try and force the wheel away from the way it's trying to go. It's a little hard to explain, but practice a bit and you'll get used to it!
 
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