Auto Repair Q&A



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Brake Rotor Replacement

Rotor Replacement

by Aaron Turpen

Often, during disc brake repair, the mechanic will find a problem with the rotor, requiring replacement. Whether doing it yourself or paying a qualified mechanic, knowing when the rotor need replacing (rather than turning) and making sure the job is done right is important. Your brakes are one of the most important aspects of your car's safety.

Tools Needed

For most vehicles, the tools needed to replace disc brakes and rotors are in the toolbox of most every home mechanic. These include: a lug wrench, a car jack, a large C-clamp, and appropriately sized sockets and a wrench to drive them. On most vehicles, a 3/8" drive socket wrench and set of sockets is it. A large screwdriver, a rubber hammer, and some brake cleaner or lubricant may also be needed if the rotor is stubborn coming off.

Removing the Old Rotor

To remove the old rotor for replacement, the car must be lifted in the air and placed on appropriate safety jacks or stands. This will mean either the entire front end (with wheel chocks at rear) or the left or right side will be up in the air.

Use caution and proper safety procedures when lifting your vehicle off the ground.

The lug nuts should be removed along with the tire and wheel. Put these to the side. The caliper will be over the top of the rotor. Loosen the release nuts on the caliper and lift off of the rotor. Use a bungee, string, or zip ties to tie it up out of the way - usually to the spring or another handy part within reach. DO NOT TIE TO BRAKE LINES as they could break.

Once the caliper is out of the way, the rotor should slide off of the lug bolts. If not, use the rubber mallet to tap it around the edges to loosen it. Spray lubricant behind the rotor may be helpful as well.

Once the rotor is removed, clean any loose rust from the knuckle, being careful of the components, and use an air jet or brake cleaner to remove dust and litter where the rotor fits into place.

New Rotor and Caliper Replacement

Put the new rotor in place. If the caliper fits around the rotor as-is, slip it into place and tighten the bolt or bolts that hold it down. If not, remove the pads and use the large C-clamp to compress the caliper's cylinder slowly back into the caliper housing. Replace the pads and put the caliper on.

Once the caliper is in place, follow your vehicle's owner's manual to properly bleed the lines (if necessary) and adjust the caliper. Most vehicles will not require line bleeding and adjustment will be automatic with the first application of the brakes from the pedal.

Put the tire and wheel back on, tighten the lug nuts, lower the vehicle, and test the brakes by pumping the pedal. If it fails to harden up after a few soft pushes, bleed the lines. If it hardens, do a "roll test" and roll the vehicle (in neutral on level ground, engine off) and apply the brakes to stop. Start the engine and do another roll test without using engine power to move the car. Drive it carefully in a safe area or around the block or parking lot to further test the brakes.

You're done!

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