Bike Forums - View Single Post - Hydraulic Disc Brakes vs. Mechanical Disc??

05-30-07 | 06:44 PM

#19

Raiyn

I drink your MILKSHAKE

Joined: Jul 2002

Posts: 15,061

Likes: 3

From: St. Petersburg, FL

Bikes: 2003 Specialized Rockhopper FSR Comp, 1999 Specialized Hardrock Comp FS, 1971 Schwinn Varsity

Quote:

Originally Posted by albyhellscream

I never understood why bigger rotors have more braking power..

Let's start by taking a look at the basic physics involved. There's a law of physics that states how an object in motion has a certain amount of energy due to its momentum. This energy is called kinetic energy. In order for this object in motion to stop or slow down, it must lose some or all of its kinetic energy. A brake does this by converting the kinetic energy to heat.

It's really easy. At your wheel you have a metal disc and a chunk of pad material. The pad squeezes or pushes onto the metal. When this happens, you create friction. Friction generates heat, of course. Since the wheel is turning, then the kinetic energy of your momentum is converted to heat at this point and discharged harmlessly into the atmosphere (with a slight loss of pad material), and your bike slows down. The faster it is going, the more heat is needed to stop it. The more pressure you apply to the pad, the faster it can discharge the kinetic energy. The larger disc aids in the discharge of the heat generated as the increased surface area allows heat to dissipate more quickly, hence better braking.

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