Tandem Tom

Wondering if someone might be able to help me with a dimension?
Center pull brake studs and cantilever brake studs. I understand stand the location of the two are different. What is the difference in millimeters?
Thanks!

Andrew R Stewart 

I would never make a published claim as to brake boss braze on spot dimensions without also specing the brakes and rims too. It is a simple exercise to mock up on paper the actual rim cross section and then the brake as it would be when clamping the rim and from that determine the boss to boss width and the axle to boss height.


Cantis have their pivot below the rim, the pads are above the arm's pivot. Center pulls have their pivots above the rim. Additionally to any post length or diameter differences between the two designs know that the spring's tab/hole/mount can be rather different too. All cantis don't have the same spring hole location as too all centerpulls don't have the same spring hole location.


When I first started this stuff (frame work) I did a lot of test fitting of wheels and brakes on the bikes that I had access to. I made notes on their dimensions and how the resulting set up actually worked. I found a few mms of too this way or that way and the set up would be really good or result in an underperforming brake that had very limited adjustment range.


Regardless of what numbers others say I strongly suggest that you test the advice in real life by a mock up before you start to cut or file any thing. Andy

dabac

AFAIK center-pull is a type of caliper brake, and doesn't use frame/fork mounted brake bosses.
Canti- and v-brakes generally use the same brake boss spacing, with some old frames/forks/brakes using a tighter spacing.
Then there is the U-brake. Generally found on BMXes and a handful of MTBs.
I guess it's this you're asking about. Unfortunately I can't help you there.

fietsbob

_1..Get them, put the wheel in the fork line the brake pads up with the rim and measure . its not difficult..

HYup its Simple.. Centerpull/U-brakes the pivots are above the rim, V/Cantilevers they're below the rim.


1st Brake adjustment with Mafac Cantilevers is where the posts go, I sorted it out in 1975, no internet crutch then.


BTW dabac, you need to read Bike Quarterly.. Brazed on boss Centerpulls are decreed the thing to have by the authorities, there..





...

Tandem Tom

Here is the reason I asked the question.
I was wondering if center pull brakes stud mounted would work on Canti brake studs. Then maybe they would have a long enough reach to use a 650b wheel.
I appreciate the replies.
Thanks!

Andrew R Stewart 

Almost all true. What you call centerpulls also can be found mounted onto brazed on bosses, much like "U" brakes and Roller Cams but with some boss dimension and spring attachment differences. Usually found on hand crafted frames of many years ago or more recently among the rando crowd.


Tom- Back in the early days of mountain biking Moots made a few bikes with moveable bosses, they were brazed onto surround clamps that could slide up and down the blades or stays as needed with different wheel diameters. I ran some common numbers and I think you'll find the pads won't come close to contacting the 650 rims, even if the bosses are otherwise compatible and of a width which works (which they both are likely not). Andy

Tandem Tom

Thanks Andy.
In my quest of possibly making my Miyata 610 a 650b without moving the studs I was considering any potential option.
I am now moving towards a 650b specific frame.

unterhausen

650 is too close to 700c for this to work. There are canti boss droppers

OneIsAllYouNeed

The existing 700c canti studs are at roughly the same radius as 650b rims. No brakes work with that arrangement. I used a "990 plate" to install U-brakes for 650b rims on a frame built for 700c canti brakes. I'd be happy to sell those parts to you for cheap.

Here's a picture with 700c rim, 700c canti brake, and 650b U-brake.