The Final Word on front disc brakes

[joe_schindler]

Originally Posted by Turbobuick

Doc,
I think you are looking at the caliper sizes a little wrong. The size of the piston does not necessarily determine the performance of a caliper. The absolute biggest determining factor is going to brake surface area, IE the size of the pad. How the caliper distrubtes clamping force on the back of the caliper, single v.s. dual v.s. four piston calipers. A dual piston PBR caliper has a MUCH larger brake pad surface area and the caliper distributes the clamping force MUCH more evenly over the rear of the pad than a stock caliper. Same thing is true for the 11" S10 balzer upgrade. That brake upgrade is going to be significantly better than the stock brakes because it has a significantly larger brake surface with calipers that distribute pressure more evenly. It's not how hard the caliper clamps but how much surface area and how it is distributed that make the difference.

There are other factors that play into this also including how the caliper is mounted. The PBR is a full floating design and not a fixed mount design like the Dynalite in the Wilwood kit. I don't know enough about this stuff but I do know that is important in a road race/ street car brake setup.

Just my point of view, thanks for compiling the info though and it is good for comparing the differences.

Swept Area.

[joe_schindler]

Originally Posted by Doc

That is only partially true...

Brakes work based on friction. The frictional force between two sliding objects is based ONLY on TWO factors:

1. The Normal Force, or in Layman's terms, the force holding the two objects together. (In our case this is the clamping force exerted by the caliper onto the pads and rotor)

2. The coefficient of friction, which is a property of the materials that the sliding objects are made of. (In our case, this has to do with the materials used for the rotor and the brake pads). When you swap to "high grip" brake pads you are changing this property.

You can look up this equation in any basic Physics textbook. Note that the AREA of the contact (for example, the size of the pads) does not enter into this equation at all. I know it is counter-intuitive, but it is true.

Now then, larger brake pads are going to be more DURABLE than smaller ones, becasue the energy lost to friction is spread out over a larger area. So yes, in a way larger brake pads and larger numbers of pistons are better in some regards: durability and resistance to heat-based fade and damage.

But for RAW BRAKING POWER ONLY, area is king.

Of course, all of the above assumes that the caliper is stiff enough to actually apply the force to the pads. If you have a caliper with giant pistons but it is too flexible to properly clamp the pads then you will never realize the benefits of all that area. As I noted at the end of my original post, the stiffness of the calipers might affect the results. I have no way to measure the stiffness of the various calipers discussed, so I can't really comment on that. However, it is something to think about.

Automotive brakes are simply a crude system for converting kinetic energy to heat. Too many people confuse a firm brake pedal with good brakes.

How efficiently the system works is dependent on swept area, friction coefficient of the pads/rotor, clamping force, and application force. It’s a system; not a magic wand.

[cocarter1]

Cannot beat the hydroboost! Way more pressure at the master cylinder.
Conrad