Originally Posted by TeCKis300 View Post
Okay, here's the definitive guide to all the wheel offset and fitment questions. Here's the real way to figure out whether your wheels will fit!

EDIT: Thanks to NeoVB for this excellent link to help visualize wheel parameters - Wheel / tire size calculator / comparer - RIMS-N-TIRES

These limits are the practical extremes with good alignments. You can buy more fender room with camber or rolling or pulling. In front, you can buy more room with shorter overall tire diameter (<25") The closer you get to these limits, the more likely you will need to stretch a tire to fit the fender side. Drop does not determine what size wheels fit. Put too aggressive a wheel, and one day, you WILL bend your fender when you take the wrong turn with a good bump if you exceed these limits.

Measuring in mm from the face of the hub:
Front fender limit: +65mm
Comments:
| +65 | Stretch tire and/or roll fender. Need fender liner mod. Do not exceed tire diameter of 25"
| +55 | Fender liner mod if going for a wide or tall tire. Do no exceed tire diameter of 25.2"
Front inner suspension upright limit: -155mm
Comments:
Need spacer if this number is exceeded. If close, do not use lip weights on wheels

Rear fender limit: +68mm
Rear fender limit w/ shaved lip: +75
Comments:
Need to stretch tire to a certain degree if very close to these numbers
Rear inner suspension coil lmit: -183mm
Comments:
Several factors matter as you approach this limit. You may need to limit the amount of suspension travel. You may need to stretch tire. And you cannot run as aggressive camber. I've been able to actually scrub tire well before this limit (@ -175mm) with track cornering loads on the spring and inner forward tub.

Equations to figure out wheel lip placement relative to limits:

Outer lip: (Wheel Width * 25.4) / 2 - Wheel Offset
Inner lip: (Wheel Width * 25.4) / 2 + Wheel Offset
Note: Inner lip is related to backspacing but backspacing takes into consideration the wheel lip thickness, which is usually another 1/2" or 12.7mm.

Examples:
Front wheel size: 8.5" +45
Fender: 8.5 * 25.4 / 2 - 45 = 62.95 (< 65 - OK)
Suspension: 8.5 * 25.4 / 2 + 45 = 152.95 ( < 155 - OK)
Rear wheel size: 9.5" +55
Fender: 9.5 * 25.4 / 2 - 55 = 65.175 (< 68 - OK)
Suspension: 9.5 * 25.4 / 2 + 55 = 175.65 (< 190 - OK)