Well, when it comes to high performance vehicles (car, motorcycle, etc), un-sprung weight is a big issue.
With calipers that are radially mounted, they offer the lightest weigh components, with the largest piston surfaces inside the calipers, and provide the least amount of flex when under pressure from the braking system as the driver applies the brakes.
Mostly, this is done for vehicle consistency.
The brakes feel the same lap after lap, when the flex of the system is kept under control.
So much has been done to a vehicle to provide great stability and braking response, and over time they realized that the brake components can actually flex the mounting bracket under extreme braking. Sliding calipers can actually bend and warp a solid rotor used under racing conditions.
So they created floating rotors to help allow the side to side movement of the caliper, yet still keep the rotor in line with the caliper’s movement.
A bracket mounted fixed caliper (non-radial) was a great replacement for sliding calipers under racing conditions, but under extreme use, the flex of the bracket would eventually lead to warped rotors, but it tends to take a more time and heat to get to that point. You could counter act this with an extremely thick, heavy duty bracket, but then you are adding weight to a race vehicle, which is a no-no.
So radial calipers came about.
Instead of the mounting bolts going through the side of the caliper into a bracket at a 90 degree angle to the caliper body, the mounting bolts go through the top of the caliper body, into a lighter weight bracket directly below it.
This mounting eliminates caliper body flex.
Rotors tend not to warp, unless there is a manufacturing defect in the rotor itself (don’t buy cheap rotors). Typically, for street vehicles, non-floating rotors are used, but extreme performance vehicles still use floating rotors, just for the little bit of extra performance it adds. Motorcycles are the most common application where floating rotors are used in conjunction with radial calipers, but mostly to counter suspension tube flex.
Here’s some pics From Crossfire and Porsche parts:
In the first pic, you see the stock front brakes on a Chrysler Crossfire. Just a standard sliding caliper setup, with a single piston on the inboard side of the caliper.
Second picture is a Mercedes fixed caliper that Crossfire owners pick up to upgrade the front brakes. Note the mounting points where the bolts go through to the mounting bracket.
Third picture is a radial caliper from a Porsche Boxster. Note the mounting bolts going through the top of the caliper, and the open area in the top of the caliper to access the pads. Quick and easy pad changes when you get to the track for racing pads, and then back over to street pads to get you home again!
BC.
