Many Ford Ranger enthusiasts have used wheels off of a Ford Mustang on their Ranger. This page will help guide in swapping to Mustang wheels. 1994/1995 Mustang 17×8 Wheels On 2004 B2300 (15×6 stock) (Contributed by crazypj) I just fitted … Continued
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The biggest challenge historically was the hub on Rangers interfered with center caps on Mustang rims. The solution has been high quality spacers.
39mm offset is a lot compared to the 0-12 for the various stock rims. You really want 25-30mm spacer to put loads on bearing back where they are supposed to be/make scrub radius positive.
Scrub radius being the point where the center of the tire contact patch and king pin (or virtual kingpin position with ball joint) line up. Positive is when the contact patch center is to the outside, negative to inside. Positive scrub radius in a RWD tends to make the vehicle drive straight. Negative makes the vehicle "dart-y".
As several posters above have stated, 99% of the time, it isn't an issue to drive with negative scrub radius. Its the off chance you have a blow out, then the vehicle will dart in direction of tire failure. Which is why you really shouldn't drive on public roads with high offset rims on vehicles not made for them.