Check and Change Brake Discs

Steps

1. Know the signs. Shaking in the steering wheel or pedal when you brake, grinding, deep grooves, a raised lip at the outer edge, cracks or blue patches all mean the discs need checking.
2. Get the right parts. Discs differ by car and by axle, so choose them for your car's engine and model years ("Parts for your car" below), with a set of new pads.
3. Park and raise the car. Park on firm, level ground, set the handbrake and block the wheels you are not working on. Loosen the wheel nuts, jack the car up at the lifting point your handbook shows, set it on an axle stand and take the wheel off.
4. Measure the disc. The smallest allowed thickness is stamped on the disc, often on its edge or hub (for example MIN TH 22). Measure the thickness in a few places on the braking surface. If it is near or below that figure, change the discs.
5. Take off the caliper. Push the pads back a little by levering gently, unclip any wear sensor, undo the caliper bolts and lift the caliper off. Hang it with a cable tie or wire. Never let it hang on the brake hose.
6. Take off the bracket that holds the pads, by its two bolts at the back. They are tight; a long bar helps.
7. Take off the old disc. Undo the small retaining screw if there is one, then pull the disc off the hub. If it is stuck with rust, tap it with a soft hammer from behind.
8. Clean the hub with the wire brush so the new disc sits perfectly flat. Rust here makes a new disc wobble.
9. Fit the new disc. Wipe off its protective coating with brake cleaner and a clean rag, then put it on the hub and refit the retaining screw.
10. Refit the bracket. Fit its bolts and tighten them to the figure in your handbook. Some cars need new bolts or thread lock here: the handbook says.
11. Fit new pads and refit the caliper. Push the piston back slowly, watching the brake fluid level under the bonnet. Fit the pads, refit the caliper and tighten its bolts to the handbook figure. Fit the wear sensor.
12. Refit the wheel. Lower the car and tighten the wheel nuts to the handbook figure, in a cross pattern. Do the other side of the axle the same way.
13. Pump the brake pedal until it is firm, before you move the car. Check that the brake fluid level is between MIN and MAX.
14. Test and bed in. In a quiet, safe place, drive slowly and brake gently a few times. Avoid hard braking at first, and follow the instructions that come with the discs and pads.