Generally brake calipers are very reliable, and thankfully require replacing a lot less often than pads and discs, but if you have to change one here's how to do it!
There are numerous different brake fitments, but in the majority of cases, cars are fitted with single piston sliding calipers which are generally fitted the same way. The caliper is connected to a carrier which is connected to the car's hub. While you can replace calipers individually the pads and discs always need to be replaced in pairs across the axle.
Do not attempt to change the caliper unless you either know what you're doing, or you have expert supervision. You cannot take risks with any element of the car's braking system.
01 Securely jack up the vehicle, using axle stands and wheel chocks and remove the road wheel.
02 The carrier is usually bolted to the hub with two bolts, these can be left in place if you're only changing the caliper – but will need to be removed if you're also changing the disc.
03 The caliper is secured to the carrier with two bolts, usually with allen heads, which secure a pair of sliding pins in the body of the caliper.
04 By removing the allen bolts you will be able to prise the caliper carefully off the disc. It may be tricky to remove, so be careful if you're using a pry bar.
05 With the caliper removed the pads will pull out – they're often held in place by clips.
06 The brake line needs to be carefully removed from the caliper. You will need a receptacle to catch any brake fluid that will spill out (do not get this on the paintwork).
07 With the new caliper ensure the piston is pushed back into its cylinder with a pair of water pump pliers, a G-clamp, or similar. Rear pistons are often of the 'wind-back' variety and need to be pushed back into the cylinder with a brake wind-back tool. These are cheap to buy, and easy to use.
08 The pads can then be refitted to the caliper (with any necessary clips or pins) and the caliper mounted on the carrier.
09 Refit the caliper sliding bolts and check that they're in good order and slide smoothly.
10 Spin the hub and make sure that the calipers are correctly located over the disc, with no binding (some light binding is to be expected).
11 With all the bolts secure the brake hose needs to be reattached, and the caliper bled to remove the air.
12 Follow the usual bleeding procedure (either with a one-person bleed kit, or with the help of an assistant, and be sure to keep the brake fluid reservoir topped up to the correct level.
13 Check all the bolts before reattaching the wheel and torquing the wheel bolts/nuts to the specified level.
14 Be aware that the brake pedal may need several 'pumps' to bring the pad into contact with the disc. Drive carefully and ensure that the brakes function correctly.