I. Fixed vs. Floating
Fixed calipers have a rigid mount to the frame or fork and in combination with a fixed rotor offer the only consistent method of achieving zero free running drag. Floating calipers are able to slide axially on shafts and allow the caliper to self center during each braking application.
II. Mono-Block vs. 2 Piece
The difference between a mono-block and a two-piece caliper is the bridge construction. The bridge is the material or structure above the caliper pistons that connects the two halves and provides the strength for clamping onto the rotor. Mono-block calipers are formed from one solid piece of material while two piece calipers are manufactured as two separate halves and then bolted together. Both styles can be designed to offer the proper strength and stiffness. Typically, more material in the bridge as well as height in the bridge will offer a stronger and stiffer caliper.
Pros and Cons:
- Creative bridge design and shape (no bolts required)
- No transfer port seal needed to connect the two halves together
- Manufacturing & Assembly can be more difficult
- Service options are limited due to the caliper being all one piece.
- Large Bore plug and seal is typically required.
- Steel bolts in bridge can offer increased strength.
- Manufacturing & Assembly is simplified
- Transfer port seal required between two halves
III. Piston Quantity
Piston quantity is relatively unimportant in regards to brake power. More pistons or larger pistons does not mean more power. Total caliper piston area is a more reliable indicator. High pressure systems with small caliper pistons can offer the same brake power as lower pressure/large piston systems. One advantage to having more pistons is packaging. A row of 2 or 3 small diameter caliper pistons on each side of a caliper can offer a large total piston area with a low profile design. Inversely, two piston calipers are usually shorter and taller.
IV. Opposed vs. Single Sided
Opposed caliper pistons stroke on each side of a rotor to meet at the rotor and generate clamp force. A single sided caliper piston strokes on one side of the rotor and either floats the rotor to the other pad, floats the caliper to contact the rotor, or deflects the rotor into the other side. Single sided calipers typically can offer very narrow packaging requirements on the inner caliper half.
A. Mechanical Advantage (MA)
The MA of a mechanical caliper comes in two forms. First, the length of the lever that is attached to the brake cable will determine how much torque is transmitted to the internals. Second the internal components contain opposing sets of ball ramps with ball bearings riding in between them. As the two sets of ball ramps are rotated in the opposite relative directions, the ramps spread apart. This spreading force is what generates the clamp loads for the caliper.
B. Rotor Deflection
Typically mechanicals are single sided calipers that work with either a floating rotor or a floating caliper mount. An alternative to this type of design is to utilize a fixed rotor and caliper. This design requires the actuating pad to deflect the rotor into the opposing pad and then generates clamp force.