There are two schools of thought on how to convert a '79 to '93 Mustang from a four bolt pattern to the more desirable five bolt pattern for rim availability. One is to attach an aftermarket four bolt spacer over the factory hubs that has a standard Ford five lug pattern to attach the upgraded tire and rim. The other is to stay with factory parts to replace the four bolt hubs with five bolt. This second option requires an expensive replacement of axles and brakes (approximately $2,400).
Look up the new tires' overall diameter and the current tires' overall diameter. These values should be no more than 0.5 inch in difference. Any greater difference will cause the speedometer to be out of tolerance. The overall thickness of the lug/stud adapter should be taken into consideration so the rims off set, and the tires do not rub on any part the vehicle.
Jack up the vehicle until all tires are off the ground and secure the vehicle with jack stands. This can be accomplished by doing one rim/tire at a time or all together. Remove the rim(s) and the tire(s).
Paste graphite to each lug nut to prevent rust and seizing. Place the new hub adapter in position and tighten the bottom bolt finger tight. Place the other bolts in place and torque them in a star pattern to 60 foot-pounds. Install the remaining rim(s)/tire(s). Paste graphite on all new five wheel studs and tighten each lug nut by hand. Start at the bottom of the hub. Install the remaining lug nuts to insure the placement of the rim is centered to the adapter. Torque to 60 foot-pounds using a star pattern.
Measure the widest part of the new tire to the roll under the inside of the fender. This is to ensure adequate clearance. If clearance is not sufficient, a new set of rims with a different offset, or adapter, will be required to fix the problem.
