The Miata is a tough car to write tech tips for--there really isn't too much that breaks on them! I'll cover a maintenance procedure here that often gets ignored, by both shops and home mechanics.
The Miata's four wheel disc brake system is self adjusting in the front, but requires periodic caliper adjustment in the rear for proper pedal height and parking brake function. At my shop, we always set the rear calipers when doing oil changes and it was usually noticed by the customers. Anyway, here goes:
There is a bolt with a 14mm head on the back of each rear caliper. Actually there are two bolts of this size, one holds the bracket for the handbrake, one unscrews to gain access to the caliper adjuster. Pull the one covering the adjuster (don't worry, no fluid should come out!) and you will find an allen type adjusting screw. It takes a 4mm wrench to turn it. The technique is to (with the handbrake off) turn the adjuster in (clockwise) while rotating the brake rotor by hand. As soon as it stops or you feel a heavy drag, stop and back the adjuster off 1/3 turn.
Make sure that the rotor now turns freely. Reinstall the 14mm bolt and repeat the procedure on the other side.
*If* your allen bolt strips.....Don't panic! You can use a magnet or a snap ring pliers (stick the points in the socket of the allen bolt and expand to grab the adjuster) to get the damaged adjuster out. When you get it out you will see that the teeth on the adjuster are ground up. Either file or grind the damaged end 'til it's cleaned up, grease it up and reinstall. A little spray grease whenever you're adjusting is always a good idea and will help prevent this problem in the first place.
Hope this helps!
The official disclaimer: Whatever tech tips we offer are based on our own experience with, and study of Miatas. Unless otherwise stated, our procedures are not "factory approved". We assume no liability for the use or misuse of the information offered. Please feel free to use these tips in club newsletters, etc. Please let me know ahead of time. I would appreciate being given the credit (or blame..).
Bill Cardell The Dealer Alternative, Inc
541 S Main St Box 308 Palisade, CO 81526
1-800-FLY-MX5S (1-800-359-6957) (orders only) e-mail email@example.com 970-464-0878 for the rest of the world...and tech advice. 1/30/97 -- The Dealer Alternative, Inc 970-464-0878 "We make Miatas fly!" http://www.dlralt.com
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