Hydraulic disc brake calipers · Floating versus opposed-piston design, piston count and area, line pressure and clamping force, brake-fluid grade and seals, fitment data
A brake caliper is the part of a disc brake that carries the pads and, when hydraulic pressure reaches its pistons, clamps them onto the rotor. For an order, settle three things: the caliper type and piston layout for the vehicle and duty, the piston bore and the pressure it works at — which together set clamping force — and the fitment, materials, finish and brake-fluid grade.
Hydraulic disc brake calipers for passenger cars, light and heavy trucks, motorcycles and off-road machines, new or remanufactured, with or without brackets. Brake pads, discs, drums, master cylinders, electric parking-brake actuators and industrial caliper brakes are outside this page.
CNFX editorial research · Sources checked October 11, 2026 · 4 sources
Akebono explains that disc brakes clamp a rotor that turns with the wheel between pads fitted to the caliper, and that there are two types: the opposed-piston disc brake, with pistons on both sides of the rotor, and the floating (sliding-pin) disc brake, with a piston on one side only. [1] It describes the hydraulic chain: the pedal force is amplified by the booster, converted to pressure in the master cylinder and carried by brake fluid to the pistons, which press the pads against the rotor. [1]
For opposed-piston calipers Akebono says the number of pistons can be increased to spread pressure evenly when pad swept area is enlarged, naming 4-pot (two pistons per side), 6-pot (three per side) and 10-pot (five per side) calipers, the last for large high-performance cars. [2]
A linked supplier describes caliper assemblies supplied complete except for pads, built from iron and aluminium alloy, with a low-drag design. [4]
Editorial note: match the caliper type to the original equipment for the axle unless the braking system is being re-engineered, since changing piston layout changes front-to-rear brake balance.
Give the supplier the vehicle or axle, OE reference numbers, caliper type (floating or opposed), piston count and bore, rotor diameter and thickness, pad shape, bracket and mounting bolt pattern, hose and bleeder threads, material and finish, brake-fluid grade, new or remanufactured, and quantity.
02
Size piston area against line pressure
Clamping force follows from hydraulic pressure acting on piston area, so the bore and number of pistons and the line pressure available set what the caliper can deliver. [1]
Editorial calculation: one 54 mm piston has an area of about 2,290 mm² (π × 27²). At 10 MPa line pressure it pushes about 22.9 kN (10 N/mm² × 2,290 mm²). On a floating caliper the reaction through the sliding frame applies the same force to the outer pad; on an opposed-piston caliper, pistons on both sides share the job, so compare total piston area per side, not piston count.
Fluid and seals must suit the system's brake-fluid grade. US Federal Motor Vehicle Safety Standard No. 116 sets minimum equilibrium reflux boiling points of 205 °C for DOT 3, 230 °C for DOT 4 and 260 °C for DOT 5, and minimum wet boiling points of 140, 155 and 180 °C; it distinguishes DOT 5 silicone-base from DOT 5.1 non-silicone-base fluids and tests fluid effects on SBR rubber cups at 70 °C and 120 °C. [3]
Editorial note: the wet boiling point reflects fluid that has absorbed moisture in service. Confirm the seal compound with the caliper supplier when a different fluid grade from original equipment is used.
03
Compare what suppliers offer
Suppliers linked to this page list brake calipers; each card links to the page reviewed.
The listings reviewed cover passenger-car, heavy-truck, motorcycle and wheel-loader calipers, new and custom; ask each for OE cross-references, piston bore, test pressure and leak-test method.
04
Trace what each part of the caliper controls
This is a functional reference built from the sources cited; it is not one maker's specification.
Fill the specification fields with values for your vehicle
A brake caliper quotation needs values for your vehicle or machine. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
Field
What it means and published values
Ask the supplier for
Bore Diameter (mm)
Piston diameter.
Bore per piston.
Piston Area (mm²)
Example: 54 mm ≈ 2,290 mm² (editorial).
Total area per side.
Maximum Operating Pressure (MPa)
System line pressure.
Rated and test pressure.
Clamping Force (kN)
Pressure × area; e.g. 22.9 kN at 10 MPa (editorial).
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Published product pages show what a company offers, not tested performance. Confirm the legal seller, maker and OE cross-references for your order. How we source and review
· Page last updated 13 October 2026
Buyer questions
What is the difference between floating and opposed-piston calipers?
Akebono says floating calipers have a piston on one side only, while opposed-piston calipers have pistons on both sides of the rotor. [1]
How many pistons can a brake caliper have?
Akebono names 4-pot, 6-pot and 10-pot opposed-piston calipers. [2]
What boiling point must DOT 4 brake fluid meet?
FMVSS No. 116 sets at least 230 °C dry and 155 °C wet for DOT 4. [3]
Sources checked 2026-10-11. Akebono is a brake maker explaining disc brake and caliper types; FMVSS No. 116 is the US federal standard for brake fluids; Sensitive Brake is a linked supplier describing its caliper assemblies.
