Disk brakes along the rim of the wheel?

Main Question or Discussion Point

Disk brakes along the rim of the wheel??

Hi friends,
I have a doubt. I heard that when we keep the disc brake along the rim of the wheel, less energy is required to stop the wheel. Why is it so?? Why is it not used in today's bikes???

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when we keep it along the rim of the wheel then torque about center of wheel increases and bike stops sooner

Disk brakes consist of a pair of calipers squeezing two parallel surfaces. Caliper brakes on a bicycle consist of of a pair of calipers squeezing the rim of the wheel. The rim surfaces are fairly parallel.

Congratulations, you've reinvented the bicycle caliper brake.

Hi friends,
I have a doubt. I heard that when we keep the disc brake along the rim of the wheel, less energy is required to stop the wheel. Why is it so?? Why is it not used in today's bikes???
Not less energy, just less force.

At the rim you won't have to squeeze as hard, but rim is moving faster, so more wheel will slide past the caliper before is stops. At the hub the torque is much greater, so you will have to squeeze much harder...but the hub is moving slower, so less wheel will slide past the caliper before it stops.

In the end, the squeeze force x area swept will be the same wherever you place the brakes.