Tire Concerns: Changing all four tires on 07 Sport Trac
Do I really need to change all four tires on my 07 Sport Trac when just one has a minor problem?
My Sport Trac is an on-demand 4 wd, the tires have less than 30,000 miles on it, one has a nick in the sidewall. Do I need to change all 4 of them?
It seems rather unjust, but the way 4WD drive vehicles are built, most manufacturers warn owners to alway have the same sized tires (meaning the outside diameter) the same when using 4X4 traction, otherwise serious damage can be produced in the differential if only one wheel has a different circumference than the others.
There is a small degree of tolerance that is built in to some vehicles but it isn't much more than about 1/2 inch.
If you can always be certain that you will not use the 4 wheel drive mode, and keep the two different tires on the non-drive axle you may be able to get by with changing only one.
A safer way to go is to replace all 4 and keep a watch on the tread depth of the new tires waiting until they get down to the same level as the older tires, then start using the older ones in your rotation (remember to include one as the spare). This way you'd get maximum life and use out of all the tires over a period of time.
The other alternative is to change all 4 and offer the 3 partially worn tires for sale to recover part of their value and lower your total investment in tires.