I've got an old MTB w/ a chainstay mounted u-brake.





How do I remove it from the bosses? I removed the allen bolt but, it won't slide off even w/ taps from a hammer. What's the trick?

Thanks.

Get some PB Blaster and spray the crap out of it. Looks to me like it's corroded on.

So, it's just the allen bolt that holds it on? The thing is, it has a tiny amount of play up/down on the post, so it doesn't seem like it's stuck from corrosion, but more like something needs to be released for it to slide off...?

Yeah the allen bolt is normally the only thing holdng it on. I wonder if the end of the boss didn't mushroom out slightly due to being over tightend. You do have BOTH sides undone right?

Yeah, both bolts removed... but each side is independent anyway. It doesn't appear that the bosses are mushroomed at the end, but I guess that would be hard to see. But for reference, I pulled off the front cantilivers with no problem - slid right off. It seems the rear brake would be in similar condition.

I've pulled on them pretty hard, and again, used some gentle coaxing with a hammer without luck. I suppose I could start prying, but I'd hate to break things... Any other ideas?

I asked tobecause sometimes one side will come off easier. Asf or any more ideas: without being there.... not really.
https://www.sheldonbrown.com/gloss_u-v.html

Just out of curiosity, what are you going to use for a rear brake after you take that thing off?

Never thought to ask him that....

Well, actually I'm converting it to a fixed gear and will be running front brake only.

Still can't get the darn thing to come off... There's gotta be a trick!

Try poping the spring out on the bosses from the back, sometimes the spring tension holds it on. It will be filling one of three holes.

Yup, tried that too. The 2nd pic above is actually with the spring removed. The brake arms can be turned freely until they hit the opposite chain stay and I can wiggle them up/down on the post about 1mm or so... but they won't come off.

If it's absolutely definite that the allen screw is the ONLY thing holding them on, I'll clamp the frame and pull on those suckers w/ all I've got... but I'm kinda leery...

Why the flip didn't ya say you were making a fixed out of it! Cut loose on them! Heck for that matter just get the Dremel and zip them off of there.

What is in the small hole in the first photo? Is that a pin of some type?

Yeah, thinking about it... but I kinda wanna make the conversion reversible. And I'm really annoyed that I can't figure this stupid thing out.

I believe it's an adjustment screw to tune the spring tension. I did try removing that, to no avail.

Shrooms!

Okay, I finally got them off. Raiyn, your theory on "mushroomed" posts was correct. There are splines around the "seat" of the brake that grip the ends of the bosses when tightened down. These slightly gnurled the edge of the bosses preventing the brakes from being pulled off.

I had to do some serious prying w/ a fat screwdriver using the chainstay for leverage to get them off. The inside of the brake bushings got a bit scratched as they slid over the edge of the bosses, but, whatever.

Thanks Raiyn and others.

That is a centering adjustment screw.

Hey chimivee! Glad you got them off! BTW: Is that a Diamondback Apex? I've got one (with chain stay U-brake) and that paint scheme looks familiar

Could be an old Specialized too. They weren't immune to the U brake folly either.