The posts are the same as canti brakes and need to be at the same height relative to the rim.
However just because a bike has canti posts doesnt mean that Vbrakes will work without problems.
Vbrakes are intended for use on the widely spaced fork blades and chainstays of mountain bikes.
Fitting them to the relatively narrowly spaced fork blades and chainstays may cause them to end up
splayed out into a very wide V. The problem with this is that the brake shoes have to be adjusted so
that they contact the rim squarely and the wide V may mean that the range of adjustment is
inadequate.
A second problem occurs when fitting Vbrakes onto a touring fork with the normal relatively narrowly
spaced blades. Vbrakes always come with very long brake shoes, sometimes as much as 70mm long and
the extra length all projects to the rear. Though it's doubtful that this extra lemgth adds anything
to brake performance, it is harmless at the rear since it just projects into empty space. At the
front though there are problems because the extra length projects back between the fork blade and
the rim and there isn't much room there when you're dealing with a touring fork. If short (what we
used to call normal length) brake shoes were offered with the necessary adjustability for Vbrakes
the problem would be solved but alas, the solution offered is long shoes which are about half as
thick as normal brake shoes. These may fit into the available space but they wear out faster of
course since there is less material and also it's usually necessary to deflate the tire in order to
remove the front wheel since the inflated tire is usually wider than the rim. I've seen suggestions
to deal with the problem such as turning the shoes around with the long part to the front (not sure
how well this would work) or simply cutting off the excess. This seems to me to offer a bit more
promise. Most Vbrake shoes seem to be moulded and I believe I'd mount the shoes so the cut end would
be at the front. Too bad the Vbrake shoes are all produced to cater to (or create) a silly fad.
Bob Taylor
