Originally posted by DaveP
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https://enderw88.wordpress.com/autom...system-theory/
Why pressure from only one side?
This can be a little confusing and some very smart people have gotten caught. But it really isn’t that hard to understand if we shift our thinking a bit. First, ignore whether or not the caliper is fixed or floating; it doesn’t matter, and in a minute you’ll see why.
Imagine that you are holding a book between your two open hands. Now squeeze on the book. If your left hand is pushing with 25 pounds of force, then your right hand has to push back with that much force or the book will move across your chest. Each of your hands is a brake pad, and the book is the rotor. The force between the pad and the rotor is only 25 pounds, not 50. And it is the force between pad and rotor that determines the frictional force generated on the brake rotor.
In this respect there is no difference between floating and fixed calipers. The other side just acts to keep the rotor centered in the caliper, one moves the whole caliper, the other moves the other pistons.
But wait! There are still two pads, one on each side. If we replace one pad with a ball bearing surface the force on the rotor from the brake caliper would be reduce about half. So we have to count both pads, but using the force generated by one side of the pistons.
This can be a little confusing and some very smart people have gotten caught. But it really isn’t that hard to understand if we shift our thinking a bit. First, ignore whether or not the caliper is fixed or floating; it doesn’t matter, and in a minute you’ll see why.
Imagine that you are holding a book between your two open hands. Now squeeze on the book. If your left hand is pushing with 25 pounds of force, then your right hand has to push back with that much force or the book will move across your chest. Each of your hands is a brake pad, and the book is the rotor. The force between the pad and the rotor is only 25 pounds, not 50. And it is the force between pad and rotor that determines the frictional force generated on the brake rotor.
In this respect there is no difference between floating and fixed calipers. The other side just acts to keep the rotor centered in the caliper, one moves the whole caliper, the other moves the other pistons.
But wait! There are still two pads, one on each side. If we replace one pad with a ball bearing surface the force on the rotor from the brake caliper would be reduce about half. So we have to count both pads, but using the force generated by one side of the pistons.
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