Originally Posted by
Chasboy
Can anyone tell me why the disks are effective? I understand that the swept area is larger but isn’t the leverage at a disadvantage with the disc being so close to the hub?
You are absolutely right. Disc brakes are at mechanical disadvantage compared to rim brakes. Disc brakes have to compensate for that by generating more braking force between the disc and the pads, i.e. by exerting more clamping force. They do it. And they do it successfully.
Originally Posted by
Chasboy
In addition, are the mechanical disk brakes as effective as the hydraulics?
Bicycle brake efficiency is capped by such objective limits as 1) wheel losing traction and beginning to skid, or 2) bicycle flipping over the front wheel. So, if your braking system can provide enough braking force to reach these objective limits, your braking system is obviously as efficient as any braking system can possibly be. Mechanical disc brakes easily reach these limits, which means that they are equally as effective as hydraulic ones.
The parameter that might differ here is not the efficiency, but rather the
precision of the braking system, a.k.a. "modulation". I.e. how easy it is to precisely control intermediate braking forces from the braking lever. Hydraulic brakes usually offer better modulation than mechanical ones.
Another parameter that might differ is heat resistance. Mechanical brakes usually resist overheating better than hydraulic ones.