V Brake or Cantilever brake mounts, installation, how to

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Indyjps

Indyjps

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I wanted v brakes on my latest project, had a donor with nice hardware. Follow along as I figure this out.

Center to center spacing on mounting bolt for the donor is 80mm, the mounts sit with the center of the mounting bolt even with the inner edge of the fork tube. 80 mm to inner side of tube.

Project bike is 82mm to inner side of tube. Pretty close. Even if they are not this close, not a problem, you'll just have to grind to fit, or plan your fixture better.

I measured donor from center of mouting bolt to top and bottom of rim edge. Top of rim 15mm, bottom of rim 35mm, this will vary on the bike you're mounting on so I decided to use top of rim, with the pads mounted in center of adjustment.

Take a look at new project with wheels mounted. Scribe top of rim on the frame on both sides. Scribe another line 15mm -that's center line of mounting bolt.

Made a quick little fixture to hold things square, do this on the donor before cutting loose.
20161022_075641.jpg
 
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I wanted to lower the height of the v brakes as much as possible, I squared up the end of the cut off mounts in the fixture. Ground down the inside on an angle as much as I thought I could, and still fit a weld.

The height here is even on both sides and helps me see if the mounts are sitting at same height on new frame.
20161022_082439.jpg

Included a pic of a scale, or metal ruler, they're a couple bucks on amazon. If you weld or fab anything, BUY THESE, get a 6 inch and 12 inch, you'll be happy that you spent $7 as soon as you start using them.
 
Canti's didn't work out, just too tight of clearance everywhere, so I got some extra practice, moved the mounts back for v brakes. Different fixture this time, slotted holes from a shelf rack.

Fixture explanation: Mounts are bolted thru the black plate, to keep them square to the world. Big nuts are just spacers, a stack of washers would do the same, spring retainers on the mounts are centered up. When its bolted in like this, you can test fit to the frame and grind as needed. red plate is just to span the chainstay and make clamping easy.

20161023_145550.jpg
 
I think canti and vbrake mounts are similar spacing as they are interchangeable. When I say similar, there are differences in manufactures or even front to back, even see them crooked. I have changed from canti to vbrakes lots of times.
 
@cman is right; they're interchangeable in terms of height, and for the past 10 to 15 years, they've been roughly the same space between posts. Old touring bikes with canti posts tend to have far less space between them than the modern ones. Also, if they're old enough, the canti posts might not have the little holes for the return springs that linear pull("v-brakes") require, as do most modern canti brakes. Other dfferences between posts, not related to suitability for cantilevers vs linear pull sets, would be how the post is mitered, and how much offset they have. Basically, unless the frame and/or fork is really old, you can run either cantis or Vs on it...
 
I just measured on the donor bike frame, removed the canti post brazing with a torch, eyeballed using the original measurements, clamped and welded the canti posts on. There is a lot of adjustment in these brakes so close was good enough. A little paint to cover the welds and it's done. The original roller cam brakes were shot so I just put on cantis. Works great.
 

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