Tire to body clearance concerns are the most important aspect of
suspension and tire modification. This will shed a little more light on this seldom pondered area...

1997 Chevy Pickup with 5" suspension lift, 35x12.50-15 Tires on 15x10 rims (standard offset)

Same result with 3" suspension, 33.12.50-15 Tires on 15x10 rims (standard offset)

4-Wheel & Off-Road Center

766 Grand Avenue ~ Hartford, WI. 53027   (262)673-4077

To further illustrate tire clearance concerns, we have a 1998 Chevy S-10 pickup with a 5" Trailmaster suspension lift installed. On the left illustrates a typical 33-12.50x15 all terrain tire mounted on the appropriate 10" wide rim with standard offset. On the right shows a 32-11.50x15 mud terrain tire mounted on an appropriate 8" wide rim, also with a standard offset.

Since the 33" tire/rim combination on the left pushes the tire outward so much (compared to stock tire on the rear), the available clearance is minimal when turning the front tires. The 32" tire/rim combination on the right doesn't protrude near as much, enabling more turning clearance. Even though the 32 is only 1/2" shorter at the top, the rim and tire width combines together to multiply clearance concerns dramatically.

Above shows the 32" tire/rim combination in a full lock to lock turning situation. The left illustrates the minimal clearance at the rear of the front wheel well, and the right show the front of the front wheel well. Even with 5" of lift, the clearance is minimal with only 32" tires. Perhaps a narrower 7" rim would increase clearances, however, at the result of slightly 'squeezing' the tire bead together, therefore possibly reducing overall tire performance and longevity. Trimming the lower fender edges also may help to fit a larger tire. If properly done, no one would even know.

The key factor in understanding why so much 'visual' clearance will not allow the same physical clearance, lies in the shape of the fenderwell itself. On a rounded fenderwell, the tire , as larger ones are fitted, follow the contour of the existing shape of the fender. Vehicles with squared off wells do not gain clearance via suspension and body lifts at the same proportion to the increase in tire size. On this type of well, the tire increases it's size both of the tire as well as the top, while the fender is only lifted upwards with a lift kit, and the ends of the fenderwell do not move outwards at the same time, of course.

As an example to the left, the truck itself was lifted 5" over stock. The tire was increased from a 30" to a 32" tire, which is only 1" on each side. However, the lower edges of the fenderwell, although lifting upwards 5", did not offer any more clearance than before, with 1" LESS clearance now, at the front and back of the front fenderwell.

The illustration shown below points out the impact the tire height, width as well as rim offset have on body to tire clearance. As the tire increases in diameter, the fender well clearance of course, decreases. However, as the tire and rim are moved outwards by an increasing rim offset, the clearance decreases even more dramatically, especially when the tire is being turned by the steering wheel. Keep in mind, this top view shows the front to back clearance, which isn't affected as much by the installation of a suspension lift.

TOP VIEW - PASSENGER FRONT

31x10.50 Stock Tire on 15x7" Stock Rim

35x12.50 Tire on 15x7" Stock Rim

35x12.50 Tire on 15x10" Deep Offset Rim