Bicycle Mechanics - I can't explain this in the 'Title' line, but I have canti brake problems

Ahh more room...

So what is happening to my front and rear brakes right now is this.

When you apply the brakes fully and then release pressure on the lever, one of the brake arms will return to its 'home' position, but one with stay on the rim. The one staying on the rim- it you touch it gentley it will snap back to it's 'home' position. I searched a little on this site and looked at Sheldon Brown's site but nothing seemed to be the same as what is happening. The bike is fairly new (2010 Opus Legatto) and there doesn't seem to be anything wrong with the springs and such inside the brake arms.

Any ideas?

Thanks for your time!!

EB

It could be a slightly bulged spot on the canti post, causing the arm to stick.
are the canti posts greased? any rust? any paint on it?

it should be bare metal and greased.

Check the brake pads for a lip on the bottom. Often that's the cause of one side sticking like that. If so, just file sand or cut it off and perhaps readjust the brakes a little.

You should be able to adjust the return spring tension somehow. Some brakes have a small screw at the base of both brake arms, some only has it at one of the arms. If the adjustment screw bottoms out you can pull the brake arm off and reposition the anchor point of the spring at the base of the canti post. Most common design is a plate with three holes in it. Then have another go at the adjustment screw(s).
Some would simpy grab the return spring and put a bit more bend in it by hand.

I would put a post issue as being a low probability. The overwhelming majority of brakes don't pivot directly against the post, but around a bushing permanently mounted in the brake arm, making them relatively unsensitive to the condition of the brake posts.

If it's not the pads then you need to check the bushings that the arms pivot on. They don't actually pivot on the post itself. There is a bushing in the arm where it fits onto the post that actually clamps into place.

I would start by taking that brake caliper off, cleaning the post and the caliper, grease/lube the post, reinstall and test it again. I have had similar problems with some canti and v brakes on some bikes that I have flipped and the clean and lube cleared the issue right up.

Check the brake pads for a lip on the bottom. Often that's the cause of one side sticking like that. If so, just file sand or cut it off and perhaps readjust the brakes a little.

Mine will do it (Tektro 720's w/coolstops) when they get worn enough that the wear groove in the rim creates a line in the pad. Just touch the arm and it'll pop back in place. I just pull the wheel and take a razor blade window scraper across the pad to remove the line.. Gently, you're not looking to shave the whole pad, just take the raised line off. Dropping the pads and sandpapering them is also effective.

Another possibility, although not so likely seeing you said the bike is fairly new, is that the braking surface of the rim is very worn and the pads are catching in the track.

Mine will do it (Tektro 720's w/coolstops) when they get worn enough that the wear groove in the rim creates a line in the pad. Just touch the arm and it'll pop back in place. I just pull the wheel and take a razor blade window scraper across the pad to remove the line.. Gently, you're not looking to shave the whole pad, just take the raised line off. Dropping the pads and sandpapering them is also effective.

Good point about the wear groove on newer rims, forgot about those, def can cause the same problem.

Another possibility in addition to bushing/frame boss binding, sleeve friction,
as a possibility,
there is also frame boss length being a little short and the ends of the bushing
in the brake caliper is binding on its ends
try loosening the fixing bolt a little and see if that makes it stop ..
you shouldn't ride with the bolt loose , but that will test for that possibility..

Reply to thread again if that is true, a little file-ing can cure that.