Back disc break is rubbing?

RedTurbo

Hello, I have looked around other forums for an answer but cant find a topic related to my issue.

So yesterday I went out biking down hill and at the end of it my back disc was rubbing the - well look at this image of it, where the red arrow is: http://puu.sh/7TgUP.jpg

This is what the break looks like altogether if this helps: http://puu.sh/7TgWg.jpg

Now, i have loosened the back wheel and moved it around, doesnt seem to make much of a difference at all. to me the disc itself doesnt look bent, could it be the wheel or hub or even frame?

I only just started downhill and yesterday was my first time, the bike was pushed, maybe I did something there?

any advice thanks...

Ouija

It's more likely your calipers moved inwards towards the wheel. Might want to loosen those two bolts in the pic and recentre it.

RedTurbo

Ok, thanks. I will have a look now, are talking about the second or first picture?

Palmer82

I think Ouija meansd loosen the bolt in the first image and realign the calliper.

RedTurbo

Palmer82 wrote:

I think Ouija meansd loosen the bolt in the first image and realign the calliper.

Yeah I did that, only trouble is I cant seem to center it, just keeps touching?

jimothy78

RedTurbo wrote:

only trouble is I cant seem to center it, just keeps touching?

Do you mean that there isn't enough room between the pads to allow you to clear both sides of the rotor, or that you just can't move the calliper far enough in one direction to stop the original rub?

you did loosen both calliper bolts, i take it?

RedTurbo

you did loosen both calliper bolts, i take it?

Well, yeah there isnt that much room between the pads and the disc itself. When I push the break, the piston does retract but hardly - is that normal??

JBA

While you're at it you may want to do your qr up!

mattv

Looks as if the disc isn't central in the caliper and one piston is out further than the other so the caliper sits crooked. Take out the wheel, use a wallpaper scraper, broad CLEAN flathead screwdriver etc to gently ease the pistons back into the caliper, or at least til they are even. Then refit wheel (properly using your quick release, it's not safe in that picture) loosen the 2 bolts then squeeze lever, tighten 2 bolts.

cooldad

JBA wrote:

While you're at it you may want to do your qr up!

photonic69

That looks like the whole caliper/brake assembly is far too close to the disk itself. (can you get a shot of the other side and the front set-up as well providing you have matching brakes front and rear?)

1st - As above. Slacken off the two caliper bolts, apply pressure to brake lever to centre pads, then nip up bolts gently whilst squeezing brake lever.

2nd - if above doesn't work, it does look like the whole wheel hub has shifted away from the cassette. I've seen this happen on a mates bike where the locknuts on the hub bearings had come loose and wound the wheel across. Take wheel out and check for freeplay of the axle with your fingers or just see if the wheel rocks when it is mounted. Also compare both ends to see if a similar amount sticks out for mounting in the drop outs. Something in that first picture is just not right with that clearance.

paulbox

cooldad wrote:

JBA wrote:

While you're at it you may want to do your qr up!

Does doing up the QR make any difference? I'd have thought that that little bit of a squeeze it provides might help a tad.

cooldad

It shifts the frame a fraction.
Also stops you dying. Which, depending on your perspective, can be good.

JBA

cooldad wrote:

It shifts the frame a fraction.
Also stops you dying. Which, depending on your perspective, can be good.

This ^^^.

paulbox

cooldad wrote:

It shifts the frame a fraction.
Also stops you dying. Which, depending on your perspective, can be good.

Lol, I know what doing up a qr does in general; I meant, does it have any effect on his brake rubbing issue

cooldad

cooldad wrote:

It shifts the frame a fraction.
Also stops you dying. Which, depending on your perspective, can be good.

jimothy78

PaulBox wrote:

Lol, I know what doing up a qr does in general; I meant, does it have any effect on his brake rubbing issue

Yes - if the frame and hub aren't under pressure, the hub won't be in the right place relative to the frame and brakes. You should always have the wheel properly secured when adjusting the brakes, otherwise you're setting them against a rotor that will be free to move slightly, and in a different position compared with when you try to actually ride it.

It's the same when adjusting hub bearings - there needs to be a tiny bit of play in the hub when it's not secured, which disappears under the pressure applied by the QR, because the whole thing is squeezed together slightly.

The Rookie

PaulBox wrote:

cooldad wrote:

It shifts the frame a fraction.
Also stops you dying. Which, depending on your perspective, can be good.

Lol, I know what doing up a qr does in general; I meant, does it have any effect on his brake rubbing issue

It can have an effect, yes. Not always though.

photonic69

Just had the same issue when changing my stem over. When reattaching the caliper to the carrier/bracket, the flex of the hydraulic hose causes the caliper to twist on the carrier and caused the same clearance issue. Slacken off bolts and align caliper by eye and nip up. Then loosen and centre by the above mentioned methods. Jobs a good 'un.