Rear brake problems - help required

Mac9

Hello all,

I'm a complete newbie and I'm having problems with my rear brakes on my Specialized Sirrus Sport 2011.

I changed the tube due to a puncture on Saturday and on Sunday I noticed that the rear brake was rubbing on the rim. I tried to move the brakes about a bit by hand but had no luck, so I tightened the small screw on the brake pad thus making the pads go further away from the rim - problem solved.

Or so I thought! I now have significantly reduced braking power on my rear wheel which I instantly noticed this morning when commuting to work.

How do I solve this problem? Too loose and my brakes aren't strong enough. Too tight and they rub!!

Any advice greatly appreciated.

nich

After you initially tighten the screw, squeeze the level hard a few times - maybe even take it for a ride - re-adjust after as your'll probably find it's changed a bit.

If the screw is coming loose, try some thread-lock to keep it done up.

Also check pad alignment, and make sure your rims are clean - just go over them a few times with a wet bit of kitchen towel until all the black stuff is removed.

If you still can't get it right, then it might be time for a new brake cable - it stretches and wears over time so might be worth replacing.

vorsprung

Mac9 wrote:

Hello all,

I'm a complete newbie and I'm having problems with my rear brakes on my Specialized Sirrus Sport 2011.

I changed the tube due to a puncture on Saturday and on Sunday I noticed that the rear brake was rubbing on the rim. I tried to move the brakes about a bit by hand but had no luck, so I tightened the small screw on the brake pad thus making the pads go further away from the rim - problem solved.

Or so I thought! I now have significantly reduced braking power on my rear wheel which I instantly noticed this morning when commuting to work.

How do I solve this problem? Too loose and my brakes aren't strong enough. Too tight and they rub!!

Any advice greatly appreciated.

If you spin the wheel and find that the brake rubs at one point on the rim then the wheel is probably out of true

Normally the spoke tensions on either side of the wheel make the wheel laterally true so that the rim is centred all the way around to be an equal distance from the brake blocks

If one of the spokes gets loose then the rim moves at that point. This warps the rim so it rubs on the brake blocks

If you think this has happened then to fix it, on the opposite side to where it is rubbing "ping" the spokes in the area where the problem is happening. Pluck them like a harp so they make a little noise. So if the rim is rubbing on the right hand side blocks, check the spokes in that area on the left hand side.
One or more of the spokes will sound more "flat" than the others. You may like to mark the spoke with coloured tape, then tighten it 1/4 of a turn clockwise at the nipples on the rim.

Tightening a spoke moves the rim over to the side the spoke is on.

Next, squeeze all the spokes on the entire rim together in pairs (as hard as you can) and spin the wheel. It should be somewhat improved. If further adjustment is required do another 1/4 turn and squeeze again

If you really can't carry out this operation then take it to a bike shop and ask to have the wheel trued

UndercoverElephant

Since you had the wheel off just before you go the problem, loosen the QR skewer, and make sure that the wheel is properly seated in the dropouts. I... erm... hear that it can be quite easy to tighten a QR skewer with the wheel slightly mis-aligned.

Blue Meanie

+1 UndercoverElephant
I've heard that too...

CiB

Mac9 wrote:

I tightened the small screw on the brake pad thus making the pads go further away from the rim - problem solved.

Or so I thought! I now have significantly reduced braking power on my rear wheel which I instantly noticed this morning when commuting to work.

Which small screw? The one on the brake pad itself? That just retains the rubber block within the metal housing. You don't really want to use those for adjustment.

Go back a step or two. The wheel should be centred in the frame. Eyeball it where it goes between the chainstays - the two lengths from the back wheel to where the pedals are. Check also that it's centred where the brakes are. Like they've already said before, you can easily not get it in right so undo the quick release and then centre the wheel, then retighten the QR. The wheel should fall naturally into a centre position anyway.

The best way to get the brakes right is is to slightly slacken the Allen key nut that secures the brake asembly to the frame, so that it moves side to side. Pull the brake lever so that the pads are firmly gripping the rim, and at the same time nip the Allen nut back up. It doesn't need to be gorilla tight, just 'done up'. Nip it up & then tighten it another ¼ turn.

All you need to do then is adjust the clearance by turning the adjuster screw that the cable runs through into the brake cable clamp. Clockwise increases the gap between rim & pads, anti-c/w closes it. You want it to be just not touching. If your wheel's out of true you won't get to this nirvana so true the wheel, as described above.

None of this is rocket science - really a bike is the simplest bit of engineering going for most of the population. If you don't fancy putting your life at risk though with badly adjusted loose-fitting brakes, get your LBS involved.

The Rookie

If you tweaked the stop screw on the brake (V-brakes according to Evans) it can have no effect on braking performance at all, so something else is happening!

Simon