Rear Brakes and Rearset Geometry
There's been a lot of talk about rear brakes, rearset brakes and the geometry. Hopefully this will clear it up.
Here's what the stock layout looks like (simplified) on my CB360. I traced it
from a photo so it's fairly accurate.
When you press down on the brake lever, it rotates on the pivot and pulls the
front lever forward. That, in turn,
pulls the drag arm, which pulls the rear lever and you come to a (screeching)
halt. The brake lever is pretty
long, so the pedal end moves a fairly long distance, but the front lever, being
so short, only moves a little bit.
That combination gives a lot of leverage, meaning the front lever can pull with
a great deal of force. The rear
lever is a little longer, so when the front lever moves "forward," the rear
lever rotates slightly more. Think of it
this way: the brake lever moves six inches, the front lever moves two inches,
and the rear lever moves four.
Now let's look at what happens when you add rearset pegs. For the drawing
below, the stock brake lever
has been cut off, leaving a short stub. The new brake lever is shorter than the
old one. The rearset lever is
about the same length as the existing front lever. When you add the rearset drag
arm, you get a new type
of geometry. It all works the same as the stock layout, but the amount of force
applied to the brakes is
changed quite a bit.
When you press down on the new brake pedal, the rearset lever rotates, which
pulls the rearset drag arm,
which pulls the stubby brake lever, which rotates the existing front lever,
which pulls the stock drag arm which
rear lever. Confused? Don't worry. It works exactly the same as the stock
layout, except for one thing:
The new pedal is half the length of the stock one, so you have to push it twice
as far and twice as hard to
get the same amount of force back at the brakes.
You can overcome part of the problem by making the rearset lever longer. The
end of it moves farther, which
makes the other levers turn farther. The downside is you have to push even
harder on the pedal to get the
same amount of leverage. All of this happens because your new pedal is
shorter than the stock pedal. There's
no way to get around it.
Now we come to the decision part. The rearset pegs give you a somewhat better
riding position, but
the trade-off is having to push the pedal harder to make the brakes work as well
as stock. In most cases
it's not that much of a problem because your front brake provides far more
stopping ability than the back.
If you use just the back brake to stop, it'll lock up pretty easily and the tire
will skid and there's a good chance
of losing control and crashing in a very embarrassing way. If you use just the
front, you'll stop more quickly
than using the rear brake alone, but the forks will compress more and the rear
of the bike will rise up, which
will affect the steering geometry, but that's not part of this lesson.
Obviously, using both brakes is the
best way to go, especially if you're racing and need all the stopping power you
can get, but if most of your
time is on the street it's not that big of a deal.
So... did the drawings and long-winded explanation help?