Callipers
A brake calliper is the hydraulic clamp that holds the brake pads and presses them against the disc. It converts brake fluid pressure into the clamping force that slows the vehicle, and can be fixed or sliding.
What it does
Fluid pressure from the master cylinder acts on one or more pistons inside the calliper. The pistons push the pads against the disc, and on a sliding calliper the body itself moves on guide pins to apply the outer pad.
Signs a brake calliper is failing
- The vehicle pulling to one side under braking
- One wheel noticeably hotter than the others after a drive
- Uneven pad wear between the inner and outer pad
- Visible fluid weeping around the piston seal or bleed nipple
- A binding brake that does not release fully
When to replace them
Callipers are not a scheduled item. They are replaced on failure, most often seizure of the piston or guide pins, or when a seal begins to leak.
What to confirm before ordering
Have these ready and the counter can usually confirm the part in under a minute.
- Left or right side, since callipers are handed
- The calliper manufacturer, from the casting mark
- Piston count and disc diameter
- Whether the vehicle has an electric parking brake on that axle
Callipers questions
What causes a brake calliper to seize?
Corrosion on the piston or guide pins, usually after moisture has entered past a perished seal or boot. Brake fluid absorbs water over time, which is why fluid changes matter more than most owners realise.
Should callipers be replaced in pairs?
It is strongly advised on the same axle. A new calliper on one side and a tired one on the other gives uneven clamping force, which pulls the vehicle under braking.
Why does an electric parking brake change the part?
Callipers with an integrated electric parking brake contain a motor and gearbox and are a different part entirely. They also need the piston wound back electronically rather than by hand.