How do you fix a loose caliper when the bolts are tight?

Answer 1

Answer to loose caliperA. First, make sure you have the correct bolts. Buy new ones from dealer or take a trip to your local recycler or used Audi parts on the internet if you are unsure.

B. Remove brake carrier from the wheel bearing housing (if this is what you can't tighten) and rotor to be sure you can gain direct access to the brake carrier mounting bolts. Acquire the correct metric tap, probably 5 or 6 mm, you maintenance manual may give you a clue, then use the tape to clean out the threads in the brake carrier mounting holes in the wheel bearing housing which is the lower part of the strut. That should take care of the brake carrier mounting bracket to which the caliper mounts and brake pads mount.

C. Now, if you are talking about the mounting of the caliper to the brake carrier being loose, then that's a horse of an entirely different color. The caliper "floats" laterally to allow the caliper to function properly and at the same time compensate for brake pad wear. There are "guide pins" in the brake carrier to which the caliper mounts. These pins with their rubber boots are what allows or provides for the lateral movement of the caliper. Before you bolt on the caliper, make sure these guide pins move in and out of the brake carrier freely but are not so loose that they have excess play from side to side. If they don't move freely, carefully remove the rubber boots and pull the pins all the way out to clean them and their channel in the brake carrier. Now lubricate the pins with a very good heat resistent grease (I like silicon grease here), reinsert them back into the brake carrier, and now reinstall the rubber boots. It is because of these rubber boots that I like the silicon grease. Now you are ready to reinstall the caliper on the newly refurbished carrier channels and guide pins. Obviouisly, if there is a lot of "play" in the guide pins, you may have to replace the guide pins and/or the brake carrier. If you found rust when you took the boots off, there is more than an even chance that the guide pin channel channel in the brake carrier is ruined and the brake carrier and the guide pins need be replaced.

There, now you are an Audi brake expert. :-)