The Hayes Users Group
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 and levers.

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.

In summary.
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 low speed.

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 coordination.

Some fellow cults and syndicates:

NADS Hompage (Nifty Avid Disc Syndicate)     MCM Homepage (Magura Cult Members)