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