Brakes not sitting correctly?

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Mavic42

New Member
Hi!
I've recently been having a problem with my single speed with the brakes not sitting properly. Both the front and back brakes won't return to the correct position after I've pulled the lever which can leave them rubbing on the side of the wheel until I re-adjust (by pulling them apart at which point they stay pulled apart until I nee to apply the brakes again).

I've had them loose, I've had them tight, I've changed the cable, changed the callipers, changed the tension on the cable, I've cut bits out of the black covering that goes over the cable because it was bending weird and putting pressure on the brakes, but I can't seem to get them to stay where I leave them. The rear brake is brand new and it still does it like my old one and I just can't figure out what it is so if anyone could help I would be very grateful!
 

Broadside

Guru
Location
Fleet, Hants
Can you provide some pictures?
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
Calliper brakes can do this. Try undoing the main mounting bolt, pull brakes on with lever and then tighten up. I also find a cone spanner is useful to position the brakes when fitted. You can usually get purchase on the brake between the frame and the calliper and adjust.
 
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Mavic42

New Member
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This is the rear calliper but it's quite difficult to tell whats going on in the picture. I tried loosening the mounting bolt, pulling the brakes, and then tightening it back up but I'm afraid it had no effect. I did notice that the washer on the mounting bolt is a concave sort of shape however the mounting point on this bike is a rather annoying flat piece of metal. Could this be my problem?
 
Location
Loch side.
Preview attachment IMG_4297.JPG
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This is the rear calliper but it's quite difficult to tell whats going on in the picture. I tried loosening the mounting bolt, pulling the brakes, and then tightening it back up but I'm afraid it had no effect. I did notice that the washer on the mounting bolt is a concave sort of shape however the mounting point on this bike is a rather annoying flat piece of metal. Could this be my problem?
I can't see that picture and you probably can't post it because you are new. Send it to me via PM and I'll post it.
 
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Mavic42

New Member
I can't see that picture and you probably can't post it because you are new. Send it to me via PM and I'll post it.
It might be because I linked it, this is a direct upload so it should work. There's not much to see anyway.
 

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Broadside

Guru
Location
Fleet, Hants
That at least shows what sort of brakes are on the bike. When you release the lever if one block stays on the rim then they just need recentering as suggested by @fossyant

If both blocks stay on the rim then undo the cable and operate the brakes with your hand. If they release fully then you have a cable problem, if they don't then the calliper itself is at fault. You can often take them apart and fully strip down, clean and regrease all pivot points.
 
Location
Loch side.
It might be because I linked it, this is a direct upload so it should work. There's not much to see anyway.
OK, those are dual pivot brakes and they can be set up to remain true.

Your first port of call is to release the centre mounting nut a bit. Then, access that grub screw you can see just above the pivot on the left side of the photo. It will be a 3mm Allen key. Now turn it and see how far it can go either way and return it to a position midway between all the way it and almost all the way out.
Now pull on your brake lever and tighten the centre mounting bolt. Very tight. Release the brake and now fine-tune the centering using the grub screw. Keep on pulling on the brake lever when working the grub screw and make sure that both pads touch the rim at the same time. Focus on that more than trying to get an equal gap on the left and right hand side.

With dual pivot brakes, the shoe on the short arm (the one in the left of your photo) wears unevenly because of a cosine error from the short sweep of that small arm. Therefore it will wear like a wedge with the small end at the bottom and fat end at the top. Have a look and see that the pad is still reasonably even. If it is badly wedged you will have difficulty centering it properly too.
 
OP
OP
M

Mavic42

New Member
That at least shows what sort of brakes are on the bike. When you release the lever if one block stays on the rim then they just need recentering as suggested by @fossyant

If both blocks stay on the rim then undo the cable and operate the brakes with your hand. If they release fully then you have a cable problem, if they don't then the calliper itself is at fault. You can often take them apart and fully strip down, clean and regrease all pivot points.
OK, those are dual pivot brakes and they can be set up to remain true.

Your first port of call is to release the centre mounting nut a bit. Then, access that grub screw you can see just above the pivot on the left side of the photo. It will be a 3mm Allen key. Now turn it and see how far it can go either way and return it to a position midway between all the way it and almost all the way out.
Now pull on your brake lever and tighten the centre mounting bolt. Very tight. Release the brake and now fine-tune the centering using the grub screw. Keep on pulling on the brake lever when working the grub screw and make sure that both pads touch the rim at the same time. Focus on that more than trying to get an equal gap on the left and right hand side.

With dual pivot brakes, the shoe on the short arm (the one in the left of your photo) wears unevenly because of a cosine error from the short sweep of that small arm. Therefore it will wear like a wedge with the small end at the bottom and fat end at the top. Have a look and see that the pad is still reasonably even. If it is badly wedged you will have difficulty centering it properly too.


Hi, sorry for taking my time to reply. I'll this a go in the coming days and pick up some grease but this has really helped! Hopefully it sorts the problem out because it's been driving me mad!
 
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