Oh... I forgot to mention that brake feel is more important than outright power
anyway. Bikes have a small contact patch. It's important to know exactly when
your tire is at max adhesion at maximum braking, and not past it. I bow out
now...bye.
Clay
On Friday, February 20, 2015 2:34 PM, ted <ted.ke...@comcast.net> wrote:
Clayton,
Your reasoning is mostly wrong, and your stick analogy does not apply.I think
you are forgetting that the straddle wire provides mechanical advantage. A
small side force on a relatively straight cable produces a large tension in
the cable. In theory, if the cable is straight the leverage is infinite. If you
correctly analyze any cantilever brake setup you will find that making the
straddle wire flatter increases the net leverage. Unless of course the cable
attachment point is at or below the pivot, but I don't think anybody makes
brakes like that.
On Friday, February 20, 2015 at 10:26:03 AM UTC-8, Clayton wrote:
I have to jump in here.. I have always been taught and discovered on my own,
that the straddle cable should be as close to perpendicular, or at 90 degrees,
to the center of the brake pad "lever" when it hits the rim. You can do this
experiment on your own. Get a stick. Tie a string to it. Lay the stick on the
ground and lift the string. Lift perpendicularly and then from different acute
angles, inline with the stick. If you lift from acute angles, the stick slides,
which is energy wasted. If you set up your brakes with a too short straddle
cable, you lose feel and the leverage forces change as you apply the brakes.
Starts out soft and weak, and increases as you apply the brakes because the
angle gets closer to 90 degrees. Over 90 degrees, and you get weak brakes. The
brake arm is just a lever. It works best, like all levers if you lift from the
end at 90 degrees. The brake arm pivot placement is basic too. Long arm on the
straddle cable side, shorter arm on the rim side. It does not matter at all
when it comes to straddle cable length. The only lever the straddle cable acts
on is the long side. The distance between the pivot and rim, and pivot and
straddle cable angle is fixed and you can't change it. After 20 years plus of
running cantilevers and being a mechanic for YETI cycles back in the heyday, a
shop manager and mechanic, I finally gave up. I run V-brakes now, which are
much more powerful, especially with long Cool Stop salmon pads. Braking is at
near disc power. I can easily do a nose wheelie, using brake power alone. The
feel is so good, I can anti-lock brake the front. Apply, feel it start to
slide, let loose and rebrake. The only thing I don't like and it is very minor,
is the hood shape on the Cane Creek Road V-brake levers. There is far more
clearance with panniers and I don't poke my calf anymore. Everyone here loves
their cantilevers. They are prettier and match the aesthetic of Rivendell. I
get that, but for me the superiority of V-brakes has become beautiful in
itself.
On Thursday, February 19, 2015 at 7:33:03 PM UTC-8, ted wrote:
Deacon,
The thing is, that definitely does not increase the leverage.
The the vertical component of the tension in the straddle cable is equal to the
tension in the brake cable (well half on each side).Lengthening the straddle
cable reduces the tension in it as well as changing the angle at which it meets
the brake arm. The vertical component of the tension stays the same, and the
horizontal component is decreased.The net result is less torque around the
brake post for a given force on the brake lever.For a wide profile brake like
the 720, where the end of the arm is barely above the pivot, the decrease in
leverage is relatively small. But it is a decrease, not an increase. To get an
increase in leverage by lengthening the straddle cable the end of the brake arm
would have to be below the pivot.
Again I'm not claiming that the longer straddle cable didn't work better for
you, just that the cause of the better can't have been increased leverage.
On Thursday, February 19, 2015 at 6:56:40 PM UTC-8, Deacon Patrick wrote:
Kellie, I went with touring in the back because I got them used and that's the
set up that was available. It's a set up common to folks who want the most
power for the front brake, and clearance for panniers in the rear.
Ted, lengthening the saddle cable make the angle of the brake cable to the
brake arm closer to 90˚, and that definitely increased leverage. Here's what it
looked like:https://www.flickr.com/photos/ 32311885@N07/14450777149/in/
set-72157645649878184
With abandon,Patrick
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