I think my disc brakes may be rubbing

[Willow]

Today my bike was making very annoying rubbing sort of noise, I think it may be the back disc brake rubbing, how do I stop it?

 

[ianrauk]

Isn't there an adjuster on the brake?

 

[Willow]

No idea is there? - I can fix things in the house now (well some of them) but only just started to get the tools out for the bike.

 

[ianrauk]

you shouldn't need tools to adjust the brake.
From memory my friends bike who has discs, there is a small red disc at the mechanism (his is red) which he rotates to either tighten or loosen the brakes.

 

[Willow]

Nope can't see anything. It's at times like this I wish I'd bought it from the bike shop in the village and not 10 miles away! It seems that as the wheel rotates the brake disc has a slight movement in it so it is not rotating in the middle of the brake pads is therefore rubbing on one side as it goes round - not a good description but I don't think I'll fiddle any more as it's new.

 

[bonj2]

things it could be:
* caliper not correctly aligned
* rotor not true (you can true it with a large adjustable spanner)
* debris in caliper (disk brakes always grind for a bit when you go through mud and/or puddles, it soon comes off though with most)

that said when I had avids they were always making a grinding noise, which was annoying but not enough to make them unusable. I upgraded to formula oros and they only grind through mud and when very wet now, and they're dead easy to change the pads! (like hopes - they're good too, my mate's got them.)

 

[dodgy]

It's usually debris that does this, I clean mine with Muc-Off disk brake cleaner, it also claims to 're-hydrate' the pads and I think it actually works because after using it, the braking seems much smoother (in a good way!).

Dave.

 

[Steve Austin]

My disc brake whistles. Wouldn't be a bad thing if it was in bloody tune.

 

[RedBike]

Disc brakes do rub.

Lift the wheel off the ground and spin it. Does the wheel spin freely?

 

[Willow]

yes but I can hear it very annoying and closer inspection shows it rubs against the brake the disc looks slightly bent. I am sure it didn't do that on the first couple of outings - I have chucked a couple of buckets of water of area to make sure it is clean.

 

[bonj2]

yes but I can hear it very annoying and closer inspection shows it rubs against the brake the disc looks slightly bent. I am sure it didn't do that on the first couple of outings - I have chucked a couple of buckets of water of area to make sure it is clean.

if the disc's slightly bent, then get a large adjustable spanner, and find the point where it is most catching on the pad, and obviously also note which side it is catching on, thus which way it is bent - then tighten the adjustable spanner on it and pull (or push) the end of it till there's some resistance, hold it for about 5 seconds then release. Test. Do it in small increments, gently at first, then increase the force if it doesn't appear to be making any difference, but it will do if you do it right. Don't bend it enough for it to visibly bend, but possibly so that the outer circumference of the disc moves roughly say 10-20mm laterally. Keep doing it and test by spinning it after each go, and do it in as many different places as necessary.
If it's *visibly* bent though i'd consider getting a new rotor.

 

[Willow]

thanks bonji, I can see what you are saying but, I think given it is only 3 weeks old I will check with shop first, as I don't want to jeopardise any warranty. Also I've looked again at front wheel and that seems to be doing it too so maybe it's just the irritating sound that's the problem rather than what it's actually doing.

 

[Globalti]

It's normal for discs to be slightly out and as Bonj says, to need a little gentle trueing. Be sure to pad the spanner so as to avoid scratching the disc.

Once you've got it running nice and true, take time to adjust the actual caliper, either by shimming the bolts or by loosening them and get the centre seam on the caliper lined up with the disc.

 

[Mr Pig]

Shouldn't you check that the disk is central in the calliper? I would think you'd get away with the disk being a tiny bit warped if it was centred between the pads.

 

[Mr Pig]

take time to adjust the actual caliper, either by shimming the bolts or by loosening them and get the centre seam on the caliper lined up with the disc.

Ooops, missed that ;0)