THE HARD WAY
There are a few critical measurements you need to make while selecting a new wheel and tire package. You’ll need to decide what diameter wheel package you want to aim for, then decide your tire package. It’s important to take note of what tire sizes are commonly available for the dimensions you’re aiming for. For example, using sites like TireRack.com, you can quickly get an idea of common sizes from their master lists.
First, place all four corners of the suspension on jackstands with the body level at your desired ride height. On independent suspension, you may need to reposition the jackstand closer to the ball joint of the control arm to get enough weight back on the spring, but do so carefully because a factory control arm may not be shaped or reinforced that far outward for a jackstand. You should also repeat these next measurements on all four corners if you intend to squeeze in the biggest tire you can to accommodate; you want to make sure there are no disparities in wheel positioning.