Brake rub - rim brakes

JustAnotherSaver

Never really been in to cycling before until this year really so have never tinkered with bikes until now. I noticed that my rear brakes were starting to rub on the rim on one side. As you look at the rear of the bike it'd be the right hand side pad. I'll move them so that each pad is equal distance from the rim but in no time at all I can hear it rubbing and sure enough that right pad is up on the rim again with the left being clear.

So i had a look at it and figured i need to be looking at where it's labelled Spring Tension Centering Screw. Maybe i'm wrong but that's what I was going at. The mounting bolts and brake cable anchor bolts have been torqued up bloody tight!!

So i figured i need to tighten the right hand screw to bring it out. Either way, whether i was right or wrong with that approach it didn't matter because it made sod all difference. The pad is still rubbing against the rim just as it was. I'll move the arms so that everything is clear, apply the brake hard a couple times and then voila the left side is clear and the right is up against the rim again.

Point me in the right direction please

fred246

As with all these systems it's understanding how they work that's the most important bit. When you apply the brakes the tension in the cable increases and pulls the arms together. Easy to understand. What happens when you release the brakes is the important bit. There is a spring on each arm that pulls the arm away from the rim. The two springs need to be roughly balanced and strong enough to overcome the friction in your cable.
The first thing is to disconnect the noodle. Move the boot away from the noodle. Normally the boot doesn't exist or is perished. They don't seem to last long and work OK without them.
Then squeeze the arms together and pull the noodle out. The arms should now be free and you can assess how the springs are working. The spring is the wire that goes up the side of the arm. This can break or dislodge from the arm. Push the arm on to the rim and see how the spring pushes it away when you let go of the arm. The springs should be quite strong and even on left and right. If you want the spring to be stronger you screw the spring tension screw in. If the spring is too strong you can loosen the screw.
To decrease the friction I spray a little GT85 around the area that says 'mounting bolt'. With the noodle disconnected you can easily remove the outer cables from the brake lever and frame. I then spray some GT85 on the inner cable so the inner cable moves freely. Move the outer cables so you get as much of the inner lubricated as you can. Then put the cables back. Squeeze the arms together and reconnect the noodle. Always remember to do that!
If the rim hits the pads intermittently when you are cycling it's normally because the wheel isn't 'true'. Truing wheels often eliminates rubbing noises but not this one by the sounds of it.

Norman_Castle

Try loosening the centering screw on the other side.

Nearlyold

Get yourself one of these or something similar.
Plus a 5 - 25 NM torque wrench if you've bought  a bike with lightweight components

cymruchris

In addition to the above - if the wheel is quick release - make sure that it's dead central to the frame. I have come across times where people haven't seated the wheel properly in the frame, and it's been a bit off-centre, which would also cause the issue you're outlining. There should be an equal gap between each side of the wheel rim and the frame that runs alongside it. 

JustAnotherSaver

Thanks for the responses.

I wouldn't have thought it's the wheel issue because as i was messing with those screws i'd then pull on the brake lever without the wheel having moved an inch and it was touching the rim.

I squirted the spring with some WD after i had a go but before i made this thread. As it's not been suggested here i'm guessing there's a good reason for that and i've made an error.

At any rate, it seems to be ok now. Whether it goes back to rubbing once i get out on the road i'll have to see.

alembicbassman

The adjuster screws may not be putting enough tension on the spring. Some mounting posts have 3 holes to put the spring into. If yours are like this then try the spring end in the top hole to give maximum tension, then adjust the screws accordingly.
You will need to remove the brake arms by unscrewing the hex bolt at the bottom of the arm. 
I usually clean and grease the mounting post too before re-installing the brake arms to ensure they run smoothly on the bushing.