When it comes to your ride, tires always make a big statement. And yes, tires can even be fitted incorrectly. It is by far from an exact science figuring out what tires fit underneath which car. Factors like height, clearance, spring, bushing condition, shock and so on that unless you take the time to get under the car yourself you will never know for sure. Is the wheel offset in your truck correctly lined up? If not you may have a big problem.
Backspacing is the distance basically from the mounting flange to the bead. There is another way that concerns tire fitting that uses the mounting flange to the farther point inside the wheel. Be sure to watch out for alterations or changes in the consistency of the metal or lug nuts. When measuring across a tire without a wheel always carefully take into consideration that the wheel when mounted will not take up the total distance of the wheel. Finally, the clearance dimension is critical, or the measurement from sidewall to sidewall. Don’t forget that with some brake systems the lug nuts might reach properly through the wheel. Still people try to fit a tire that is too wide or narrow on a rim.
So you have everything measured, you have accounted for real world factors and conditions, and you have the new tires ready to go. This entails fitting some lubricant to the tire bead and rim edges, and using a turntable to help get the tire onto the rim. Tire fitting is not recommended unless you have the proper tools and are able to take the right safety precautions. Tires that are overinflated can be very dangerous and potentially life threatening especially when they explode as parts of the rim can shatter and act like shrapnel.