Cantilever Cable yoke

[David Waters]

Hey all, I have just been having a bit of a read up on
Sheldon Browns ideas on cantilever brakes. My set up is
currently Avid Shorty 6 calipers and shimano ultegra levers.
Am I better off using the shimano A or C type straddle wire,
or would i be better off buying an old fashioned two piece
yoke? Would the latter provide more scope for adjustment.

(The brakes are currently off the bike, and I managed to
totally f*** up the existing C wire the other day (see late
night maintenance threead!)

thoughts please...

 

[Peter B]

"David Waters" <[email protected]> wrote in message
news:[email protected]...
> Hey all, I have just been having a bit of a read up on
> Sheldon Browns ideas on cantilever brakes. My set up is
> currently Avid Shorty 6 calipers and shimano ultegra
> levers. Am I better off using the shimano A or C type
> straddle wire, or would i be better off buying an old
> fashioned two piece yoke?

Two piece yoke? Dunno what that is but I long ago fitted a
one piece centre-pull type yoke to cantis. The benefit is,
assuming no mudguards, that you can keep the straddle wire
short which gives a less spongy feel to the brakes and
probably increases mechanical advantage.
--
Regards, Pete

 

[Bruce McAdam]

"Peter B" <[email protected]> wrote in message news:<[email protected]>...
> keep the straddle wire short which gives a less spongy
> feel to the brakes and probably increases mechanical
> advantage.

On the contrary, a spongy feel indicates more mechanical
advantage.

High mechanical advantage means that when the pads have made
contact with the rim if you continue to pull on the brake
lever the force from you fingers is magnified sufficiently
to compress the pads and bend the brake arms. This results
in a spongy feel.

Low mechanical advantage means that the force of your
fingers is not
magnified sufficiently to allow the pads to compress and
arms to bend.
So when the pads hit the rims you will be unable to pull
the lever
any further. This results in a firmer feel (but less
braking force).

Avid recommend using the longest stradle wire that will fit
in the gap available http://www.avidbike.com/7_techinfo/Shorty6&Ti-
0202.pdf

Bruce

 

[Peter B]

"Bruce McAdam" <[email protected]> wrote in message
news:[email protected]...
> "Peter B" <[email protected]> wrote in message
news:<[email protected]>...
> > keep the straddle wire short which gives a less spongy
> > feel to the
brakes and
> > probably increases mechanical advantage.
>
> On the contrary, a spongy feel indicates more mechanical
> advantage.
>
> High mechanical advantage means that when the pads have
> made contact with the rim if you continue to pull on the
> brake lever the force from you fingers is magnified
> sufficiently to compress the pads and bend the brake arms.
> This results in a spongy feel.

The sponginess may also be due to flex in the system which
wastes effort. IME the most powerful brakes I've used, both
cable and hydraulic, have the least sponginess.

> Avid recommend using the longest stradle wire that will
> fit in the gap available http://www.avidbike.com/7_techinfo/Shorty6&Ti-
> 0202.pdf

But Avid also state: "A shorter straddle wire with a lower
angle will feel softer at the lever <your point>, but has
more leverage <my point>"

So I'll concede I may be wrong about the sensation but not
about the mechanical advantage ;-)
--
Regards, Pete

 

[Bruce McAdam]

> "Bruce McAdam" <[email protected]> wrote in message
> > On the contrary, a spongy feel indicates more mechanical
> > advantage.
>
> > High mechanical advantage means that when the pads have
> > made contact with the rim if you continue to pull on the
> > brake lever the force from you fingers is magnified
> > sufficiently to compress the pads and bend the brake
> > arms. This results in a spongy feel.

"Peter B" <[email protected]> wrote in message
> The sponginess may also be due to flex in the system which
> wastes effort. IME the most powerful brakes I've used,
> both cable and hydraulic, have the least sponginess.

You are not comparing like with like here. (You are
comparing different brakes, rather than different
configurations of the same brakes.)

The source of the sponginess is due to the flex in the
system. Given a choice between brakes with low flex and a
brake with high flex go for the brakes with low flex --
these will transfer more of the force from your fingers into
the brakes and will feel less spongy. But when setting up
the brakes, if you want higher mechanical advantage you will
increase the sponginess.

High mechanical advantage is not necessarily a good thing.
It requires you to pull the lever further (and when the
lever touches the handlebar you can't brake any harder). It
puts additional stress on the cable clamp, which could make
the cable slip (and when the cable slips your brakes become
useless). Under exteme circumstances it could bend or damage
the brakes, forks or rims.

Bruce