Cantilever brake bosses query

captain_vimes
captain_vimes Posts: 262
edited July 2014 in Workshop
Advice please!

I have just bought a nice set of 2nd hand carbon forks for my touring bike build. It is made for cantilever brakes and I have a nice set of Tektro Oryx ready to go on.

However the bosses, which start cylindrical, have an octagonal base to them, something I have not seen before. The brakes I have, and those others I have checked on line, all have circular holes to slip over cylindrical bosses.

Are there two types of boss and I need to find brakes that fit this kind? Or am I missing something here?

Ta!

Comments

  • ElectronShepherd
    ElectronShepherd Posts: 227
    I'm a bit confused. The circular hole in the brakes doesn't fit over the boss on the frame - you screw a threaded axle into the boss, and the brake arm pivots on this.
  • captain_vimes
    captain_vimes Posts: 262
    Hopefully these pics will help?

    Here's what I am used to...

    CIMG0128_zps8f1038af.jpg


    And here are the carbon forks...

    CIMG0129_zps53567038.jpg
  • ElectronShepherd
    ElectronShepherd Posts: 227
    Still confused!

    Old and new both have a boss that the brake arm will slide onto, a hole for one end of the spring, and are threaded internally for the bolt that keeps the brake arm on the boss. The octagonal base you mention (looks hexagonal to me, but never mind) is used to screw the post into the frame and put a spanner on it to tighten it up.

    The hole in each brake arm should fit smoothly over the end of the post, and butt up against the slightly bigger round metal collar. If it slides over the larger metal collar and hits the hex nut, either the post is too small or the hole is too large.
  • sungod
    sungod Posts: 17,350
    ^^^this
    my bike - faster than god's and twice as shiny
  • captain_vimes
    captain_vimes Posts: 262
    In that case it is simply the little metal 'pin' that is too short as it does not reach from the brake to the holes. I will have to have another play and see if there is anything I can do.

    Ta chaps
  • sungod
    sungod Posts: 17,350
    ahhhh, just looked closer at the pics

    i think that fork is for v brakes not cantis - could be wrong as i prefer not to touch either with a bargepole, but if that's the case i assume you can't use the oryx cantis on it

    does the fork have a central hole to mount a proper brake? if it does, i'd use that instead, may need a deep drop like shimano r650 (mine did when i removed the dire oryx ones...)
    my bike - faster than god's and twice as shiny
  • earthvspace4XTuUWcX
    earthvspace4XTuUWcX Posts: 322
    Simply unscrew the posts off your old forks and put them on your new ones.

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