Disc brake rub

Trigger369

Senior Member
Hi all.
I've just fitted new 50mm rims.
New rotors ,cassette, chain as well. I never thought of new break pads. So just went with the ones I had on probably near 2summer seasons.
After changing wheels over I had a bit of break rubbing . So took pads out pushed pistons back ,pads back in , loosend of bolts and re aligned while holding lever and tightening bolts.
There is still a little rub after that.
So should I get new pads ? Would it need bleeding or topped up?
Cheers folks
 

Kajjal

Veteran
Location
Wheely World
Best to try getting up to speed a few times and braking hard to settle the brakes in again. Also make sure the wheel is correctly and tight enough, more of a problem for qr rather than bolt thru wheels. Another thing to check is nothing has got behind the pad like a small stone etc. sometimes there can be a little too much fluid in the system which makes the pad to rotor clearance very tight and difficult to set without rubbing, this is solved by opening the bleed port on the brake lever, gently pressing the pads back, wipe away excess fluid, while holding pads back tighten the bleed port screw back up. Be careful to do slowly / gently to make sure no air gets it and can be easier with someone helping you.
 

si_c

Veteran
Location
Wirral
The rotor is likely in a slightly different position compared to your old wheels. You need to align the caliper properly, replacing the pads or bleeding the brakes won't help in the slightest.
 

rogerzilla

Legendary Member
This is a frequent problem. The clearances are very small (which is where the huge mechanical advantage comes from - necessary because the disc is much smaller than a rim).

On cars, the pads are not actively retracted as they cause little drag when there is no pressure in the brake lines. Slight runout of the disc and flexible piston seals achieve a bit of clearance anyway. On unpowered bikes, even the slightest drag is unacceptable, so there is generally a spring arrangement of some kind.

Anyway, to get to the point, you probably need to lose some fluid. Is it DOT 5.1? On some systems, like Avid Elixir, it absorbs water from the air so quickly that it needs bleeding every few months to eliminate the increase in fluid volume that is causing the brakes to drag.
 
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Trigger369

Trigger369

Senior Member
Well thanks everyone for the replys . I managed to fix the break rub . I was rummaging through some cupboards in the shed and found a wee tool i forgot I bought. I undone the caliper bolts a bit slid in the wee tool on either side of thr rotor and pads then pressed the break lever and tighten bolts agian .and it worked a treat .
 

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SpokeyDokey

64 and a little bit.
Moderator
Well thanks everyone for the replys . I managed to fix the break rub . I was rummaging through some cupboards in the shed and found a wee tool i forgot I bought. I undone the caliper bolts a bit slid in the wee tool on either side of thr rotor and pads then pressed the break lever and tighten bolts agian .and it worked a treat .
What is that thing? Never seen one before.
 
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goosegog

New Member
Location
North Yorkshire
 
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