* Caliper Piston Not Fully Retracted: This is the most common cause. When you compress the caliper piston to install the new pads, it's crucial that it retracts fully and smoothly. If it's sticking, it'll constantly press the pads against the rotor, causing drag. You may need to use a caliper piston compression tool to ensure it's fully retracted. Also check for any binding or corrosion in the caliper slide pins. These need to be lubricated (with caliper grease, *not* general purpose grease) and move freely.
* Caliper is Seized or Damaged: The caliper itself might be damaged or seized, preventing it from releasing properly. This is less likely if the piston retracts, but if you have significant drag and the piston retraction doesn't resolve it, you'll need to inspect the caliper closely.
* Parking Brake Engaged (partially): Make absolutely sure your parking brake is completely disengaged. A partially engaged parking brake will cause significant rear brake drag.
* Worn or Damaged Rotor: While you installed new rotors, it's possible one of them was damaged during installation or is warped, leading to contact even when the brakes aren't applied. Check the rotor surface for any unusual wear, scoring, or warping.
* Incorrect Pad Installation: While less likely, ensure the pads are seated correctly in the caliper and aren't binding against anything.
Troubleshooting Steps:
1. Verify Parking Brake: Absolutely the first thing to check.
2. Check Caliper Piston Retraction: Use a caliper piston compression tool if necessary to fully retract the pistons. Then, lubricate the caliper slide pins (the pins that allow the caliper to move freely). Use caliper grease, *not* anything else.
3. Inspect Calipers for Damage or Seizing: Look for any signs of rust, corrosion, or binding. If the calipers are damaged, they'll need to be replaced.
4. Inspect Rotors: Carefully inspect the rotors for any damage, warping, or uneven surfaces. If a rotor is damaged, it will need to be replaced.
5. Test Drive (carefully): After addressing the above, test drive the vehicle VERY carefully. If the drag persists, you may need professional assistance.
Safety Note: Driving with significant brake drag is dangerous. It can overheat your brakes, leading to brake failure. Do not drive the vehicle extensively until the problem is resolved. If you are unsure of how to proceed, have a qualified mechanic diagnose and repair the issue.
