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Caliper Kit

Caliper Kit

Learn and Shop: Caliper Kit

Hydraulic systems incorporate two cylinders; a force on an input cylinder transfers force to an output cylinder. In a braking system, the brake caliper holds the output cylinder. Commonly this cylinder is called a piston, or, in some slang terms, a "pot."

Free Floating Calipers

Many original equipment calipers have a single piston. In order for the caliper to place load on pads on both sides of the rotor, single-piston calipers act like a clamp, and float on caliper "pins" which slide in the caliper bracket to allow the clamping caliper to slide easily as pressure is applied and released. Whether these "free-floating" or "sliding" calipers have one piston or multiple pistons, it is critical that the caliper pins be clean and well lubricated for proper function. It is also noted that the caliper bracket in free-floating caliper applications also holds the brake pads. The pads sit in clips in the brackets, sometimes held in place with springs or other retainers.

Rigid-Mounted Calipers

Performance calipers are typically made of aluminum and often have 4, 6 or more pistons. These calipers mount rigidly to the hub carriers centered over the rotor, with pistons placed on opposing sides of the rotor. The primary advantage of using racing calipers is rigidity. They will offer a more firm and direct braking with less flex, even as temperatures rise. They can come with brackets that allow radial mounting (where the caliper mount bolts are perpendicular to the axle), which is more rigid than conventional standard mounting (where the caliper bolts are parallel to the axle). They can be mono-block (one-piece) or constructed of multiple castings, forgings, machined from billet stock. Intrinsically, multi-piece calipers are more rigid in performance situations, as the steel bolts which assemble twin-block calipers maintain stiffness better than the aluminum caliper bodies on mono-block calipers as temperatures rise.

Caliper Issues

Possible issues with calipers of all kinds involve sticking or leaking piston seals. Caliper piston seals are designed with a special shape to allow the piston to retract when pressure from the pedal is released. Seizing pistons will have a similar impact on drivability as sticking caliper pins. Sticking pins or pistons can result in excessive noise, reduced fuel economy, premature rotor or pad lining wear, and vibrations. Other tell-tail signs of severely sticking calipers include discoloration of a rotor from over-heating, excessive brake dust on the wheel, or excessive smoke or odor from the brakes.

Since floating calipers are allowed freedom of movement, they are more tolerant of disc or hub irregularities. Racing calipers are more particular about the disc quality and dimension, as they do not have the ability to absorb excessive runout.

Piston Count

Due to the nature of hydraulic systems, the sizing of the pistons in the master cylinder and caliper pistons/wheel cylinders must be changed in proportion to maintain pedal travel. It is common to think that upgraded brake calipers will have larger pistons on them. However if a piston is changed to be larger without a corresponding change in the master cylinder piston size, the pedal will travel further than expected before the pads engage. Instead, upgraded calipers will have multiple smaller pistons to maintain a more factory pedal-travel, with more even pressure on the pads. Some caliper manufacturers will produce directional calipers where piston sizes are staggered to give further refinement to the caliper performance. The degree of sophistication in caliper design results in a dramatic increase in cost, leading to a very wide spread in caliper pricing.

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