Section 04-04: Wheels and Tires | 1993 Mustang Workshop Manual |
To equalize tire wear, tires may be rotated, but not until the cause of unusual or uneven tire wear is determined and corrected.
Front and rear tires perform different jobs and can wear differently depending on the type of vehicle and driving habits. To equalize wear and optimize tire life, rotate tires at approximately 12,000 km (7,500 miles) and then each 24,000 km (15,000 miles) thereafter.
If abnormal wear is detected, find and correct the cause, and rotate the
tires following the diagram to allow more even wear. 
Use only uni-directional tire 4 tire rotation for Cobra P245/45ZR17 tires. 
CAUTION: Never use the temporary spare for tire rotation or as a regular tire.