What Does Wheel Offset Mean? (And How To Measure It)

Have you ever noticed a car, truck, or SUV with its tires sticking farther out to the sides than other similar vehicles and wondered how, or why, they're like that? How they got them out there has to do with wheel offset, negative wheel offset to be more precise in this case. 

Before we dive in too deep, we should agree on some wheel terminology so we're all on the same page. When looking at the red-painted surface of the wheels pictured above, we'll call that the face, or front, of the wheel, and the surface directly opposite the face is the rear of the wheel. The part of the wheel that meets the rubber of the tire we'll refer to as the rim (I know, wheels are sometimes called rims but stick with me for now). The lug nuts hold the wheel to the vehicle by threading onto wheel studs that are attached to the car's axles. The inner flat part of the wheel that contacts the face of the axle we'll call the axle-mounting surface.

A wheel with zero offset has its axle-mounting surface equally spaced between the rims at the face and rear of the wheel. A wheel with positive offset has the mounting surface located closer to the face of the wheel, while negative offset wheels have the mounting surface towards the rear of the wheel.

Measuring wheel offset is easiest if the wheel is removed from the vehicle with or without the tire in place. Start by laying the wheel face down on a flat surface such as a garage floor. Next, lay a straight edge across the wheel's rear-most rim or the tire, making sure it's long enough to reach all the way across. A board or long carpenter's level is a good tool for this purpose.

Measure from the floor to the bottom of the straight edge through the wheel's center bore with a tape measure or rigid scale and divide that measurement by two to find the wheel's center value. Then measure from the axle-mounting surface to the straight edge. If that value is more than the wheel center, subtract the smaller value from the larger value to reveal the wheel's positive offset. If it's less than the wheel center value, subtraction again reveals how much negative offset the wheel has.

In 2009, I bought a stock 2000 Jeep Wrangler Sport, commonly referred to as a TJ by Jeep lovers. Within the first two weeks of ownership, I took it on a trail run with a four-wheeling club and encountered what they referred to as "The Rock Garden." It was a dry riverbed strewn with microwave-sized boulders through which they'd marked a pathway with orange cones. My little yellow TJ scraped and crawled through it, losing part of the rear bumper along the way, but I was hooked.

While preparing to modify my Jeep to take it off-road more comfortably, I ordered a lift kit, bigger tires, and new bumpers. Fortunately, while I was shopping for tires, the salesperson convinced me to buy wider wheels with enough negative offset to provide clearance for the bigger tires. For reference, the stock tires on my Jeep were 215/75R15, measuring almost 28 inches outside diameter, 8.5 inches wide, and fit a 15-inch rim. The new 33x12.5x15 tires on order would fit the same 15-inch rim, but they were 4 inches wider and over 5 inches larger in diameter. While the extra lift would raise the body for some clearance, wheels with increased negative offset helped prevent tire rubbing.

In addition, many performance cars featured widebody kits to increase aerodynamics and allow the use of wider tires on negative offset wheels. Still, others used wheel spacers to increase the negative offset of stock wheels. However, when considering new wheels to replace the stock setup, it's a good idea to know your wheel offset and remain close to it.