Could a mechanic be this bad?

[Timshady75]

Towards the beginning of 2008, I took my wife's 2000 Explorer in for service and had the front tires replaced. The guy I took the car to (a friend of a friend deal) installed Toyo Open Countries. Towards the end of the year, December I believe, her car was back in and had the rear tires replaced as well. Almost immediately we noticed an occasional shuttering when driving lower speeds... my wife said that it would stop once she got up over 40-45 mph. As it got worse and more often, we took it back to the guy and he told us that it was a bad rear diff but he didn't work on rear ends. So we took it to another guy (a friend of a family member) that started working on it and immediately diagnosed that it was the transfer case. When he started looking at possible causes for what would tear up a case so bad, he discovered that we had mismatched tires. The fronts were P255/70R16 and the rears were P225/70R15. So, now I have to go back at the original mechanic for 2 new tires and a new transfer case. Comments?

 

[IZwack]

I think you mistyped "R16" on the last tire size.

But to get back on point - not only must the tires be the same size, they preferably should be all changed at the same time or else the computer will engage and disengage the 4wd system thinking one of the axles is slipping due to the minute differences in radius between the new tires and old tires.

 

[eXcali]

Your talking not only a difference of 3 inches in the tire, but a 1 inch difference in the rim size. Every mechanic makes mistakes, but a mistake on this lvl is unheard of. You can't mount a 15 inch tire on a 16 inch rim or visa-versa. So this brings the fact that you had non-matching rims to begin with. I also find a 3 inch difference not being noticed to be pretty hard to swallow. The rear tire sized you stated are smaller than stock and the fronts larger.

It just seems very odd... I wonder how the vehicle has 2 different size rims, and how a 3 inch tire difference would not be noticed.

 

[X6StringerX]

One red flag I see here is that you indicate two different sized wheels. Is this a typo? If it's not, you must have had mismatched tires before also.

EDIT: My bad, I'll refresh the thread before posting next time to see if someone beat me to it, lol. One thing I can add is that with a difference that large, you should have noticed something was up practically as soon as the vehicle was driven on a hard surface. I would imagine the vehicle would buck and jerk violently with such a large difference in tire diameter.