Power vs Modulation
Time to dispell a few more myths.
Lets talk modulation.
Brakes work by creating friction between the pads and the rotor.
The amount of friction you get depends on the pad and rotor
compound and also the force applied across the pads. The amount
of friction you get is directly proportional to the amount of
force you apply across the pads.
Now on any given brake the force you apply across the pads is
directly proportional to how hard you grab the lever. On a
system with more leverage you'll get more force at the pads
for the same force at the lever. On a hydraulic system the
force at the pads is the lever force multipied by the ratio
of (slave cylinder area)/(master cylinder area). On a cable
brake it's just leverage and depends on the design of the ramps
Regardless of the design (unless you've got a whole heap of
flex somewhere) the force on the pads is proportional to the
force at the lever.
Squeeze harder and you get more friciton and more braking
power. Some designs have more power (higher leverage) some
have less power (lower leverage). The amount of modulation
you have on each design is exactly the same (it's proportional
to lever force remember). The only change is how hard you need
to pull that lever.
Now let's discuss friction.
Friction is the electric attraction between two surfaces, the
slower two surfaces are moving the more electric connnections
can be made and the higher the friction. The faster two surfaces
are moving the less electric connections that can be made and
the less friction.
Applying this means you've got the most brake power when you're
staying still and the least brake power when you're moving fast.
Hence a brake which may feel grabby or extremely powerful at
slow speeds (e.g. car park test) will be less grabby and well
controlled as the speeds pick up.
A brake which feels well controlled at slow speeds may be
seriously deficient in power at higher speeds.
There are ways to get around this but not on a non powered
bicycle system. On a powered vehicle system the amount of
assist can be tuned to help more at high speed while providing
low speed feel.
Disc brakes operate at lower speeds than rim brakes for any
given ground speed, this allows for a smaller overall speed
change and more consistent braking at high speed compared to
A brake which peforms well at speed may feel grabby at low
speed, a brake which feels great at low speed will lack power
as the speeds increase.
The amount of modulation you have is only limited to your own