I have two bikes from the same manufacturer, and originally both bikes had the same brake model fitted.
On bike #1, I upgraded to some Avid SD Ultimate v-brakes and used them for some time.

Now I want to move those Avid v-brakes to bike #2...
However, when I tried to fit them, it is painfully obvious that they will not fit those v-brake bosses.
But they fit bike #1 just fine.

It is not a question of "use a block of wood and hit it with a hammer"... while I do not own a caliper measuring tool, it is clear that the brakes do not even begin to fit onto the bosses.

So are there subtle variations in v-brake boss sizes??? Is it a question of one size vs. another, or is it just production variances or different boss manufacturers?

Am I likely to be able to take the bike to my LBS and have them install slightly smaller ones.
(alternatively I guess I could just hand them the brakes & bike and pay them to "Make it work"... )

I think someone would have to file down the existing bosses if they are going to work. Or maybe use a heat gun to heat up the v-brake barrel and THEN use a block of wood & hammer + lube!

Anyway, I would certainly appreciate your advice. Thanks!

PS. bosses on both bikes are clean, lightly greased, free of paint, etc etc.

Never come across that particular problem myself, so I don't know how much help I can offer.
Some frames/forks (particularly those who also have disc brake mounts and Al frames) have removable bosses. It's an easy thing to look for, so start there.

Otherwise, grinding down the bosses should work. I've never seen a brake pivot directly against the brake boss, there's always been a bushing pressed into the arm that deals with the actual movement, so you wouldn't have to try for a perfect surface if you decide to go that route.

Not that it makes any difference now, but what make and model are the frames?

Tim

Hi Tim,

They are actually folding bikes - made by Dahon.
I've dropped a note on the company's technical forum also
(Helios P8 ~ fits, Speed P8 ~ doesn't fit)

dabac is correct that there is a bushing of sorts in the Avid SD brakes.
So there does not need to be rotation of the brake around the boss, but rather around the bushing.
I just need to get the darn thing fitted somehow...

How much are you missing it by? - is the boss clearly a different diameter, or is it just a matter of a tight fit? I recently had the same problem on an older bike, and in resolving the problem I learned that it is not uncommon for the bosses to mushroom out a bit under the pressure of the fixing bolt compressing in on them. The LBS had a small cutting tool/mill that we fit over the boss and twisted it down the length of the stud -- it mills it back to size. Worked like a charm and the canti arm slid on with no problem.

Great info thanks!
Yes I think it is in need of some milling, if not a new boss entirely.
With that in mind, I will leave this to the professionals ~ scheduled an appointment at the LBS.
Better than "finding a bigger hammer" anyway.
cheers

Perhaps some part of the brake is hitting some part of the frame? I have had this problem with newer suspension forks (mfrs assume users will be using disc brakes and put the v-brake mounts on as an afterthought).