scale

I have a early 90s stumpjumper.....and i went to throw some cantiever brakes on it out of the parts bin but the bolts i have that thread into the cant posts are too long ? They seem bot bottom out in the studs. I suspect they must make different sizes of this bolt and maybe i just need the next size shorter? Ive never had this happen before and dont have another set of bolts to check with. Do they come in different sizes....longer and shorter depending on the canti post/brake being used?

Rolla

Yes, they make bolts of different lengths -- often 15, 20 or 25mm. Canti brake bosses are typically 15mm in length; it might be possible that the bolts you're using are for something else, or perhaps there's a nut or something missing from the brakeset?

Andrew R Stewart 

Canti bosses that are a 1 piece machined construct usually have the threaded post hole all the way through. The theory being ease of making and allowing a longer bolt to best support the canti post at it's bottom.

Bosses that are of a folded box base with a crimped on post (usually wanting a tad of filler to secure) don't have that through hole for the bolt. Andy