rear-mount brake posts

eldunco said:

Re: the mounting of cantilever (v-brake) posts on the rear of the fork.

OK, so when they fail from fatigue fork blades do so with cracks
originating on the rear side of the fork.

Could it therefore be said to be generally unwise to braze fittings to
the back of the fork blade, the most stressed surface, both in terms of
creating sections of rigidity and risking degradation from heat
effects?

Duncan Bourne

In general, brakes mounted on the rear side of the fork will run into
some piece of the frame when the front wheel is turned. In the case of
cantilever brakes, mounting the brakes on the rear of the fork will
cause hard interference between the frame and the brake cable.

I had a bike with rear-mounted brake posts: a Lightning recumbent. The
mechanical tomfoolery I put up with to keep them working properly is
not something I'll soon forget.

Jeff

JeffWills said:

...
I had a bike with rear-mounted brake posts: a Lightning recumbent. The
mechanical tomfoolery I put up with to keep them working properly is
not something I'll soon forget.

I have ridden a couple of Lightning P-38's with V-brakes mounted on the
front of the fork. On both bikes, turning sharply to the right would
apply the front brake, as the cable hit the lower boom strut! 🙁

--
Tom Sherman - Fox River Valley (For a bit)

eldunco said:

Re: the mounting of cantilever (v-brake) posts on the rear of the fork.
OK, so when they fail from fatigue fork blades do so with cracks
originating on the rear side of the fork.
Could it therefore be said to be generally unwise to braze fittings to
the back of the fork blade, the most stressed surface, both in terms of
creating sections of rigidity and risking degradation from heat
effects?

There's no obvious cable route for cantilevers but you
probably could mount a linear brake that way.

There's no history of cantilever/linear post failure on the
front so you seem to have a solution for an as yet inchoate
problem.

Do you really find cracks on the back of a fork blade?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi said:

eldunco said:

Re: the mounting of cantilever (v-brake) posts on the rear of the fork.
OK, so when they fail from fatigue fork blades do so with cracks
originating on the rear side of the fork.
Could it therefore be said to be generally unwise to braze fittings to
the back of the fork blade, the most stressed surface, both in terms of
creating sections of rigidity and risking degradation from heat
effects?

There's no obvious cable route for cantilevers but you
probably could mount a linear brake that way.

There's no history of cantilever/linear post failure on the
front so you seem to have a solution for an as yet inchoate
problem.

I'm not offering a solution, I'm asking a question. Do the esteemed
minds think rear-mount posts are a bad idea because they modify the
rear of the fork blade.
I don't like the idea myself but I don't know if I'm being rational.

Quoted message said:

Do you really find cracks on the back of a fork blade?
--

Yes. Generally, as I understand it, if your fork fails from fatigue the
crack will start at the back of the fork blade. If the steerer fails
from fatigue I believe it often does the same though I know less about
this.

Duncan