Wheel and Tire Fitment - Fit More Tire!

It’s critical to remember that on most cars the uppermost peak of the wheel lips is usually the area of greatest clearance. As Kingsland rotates the “T” forward the well lip rolls inward toward the rocker, and the clearance drops quickly down to 9.5 inches. However, by referencing the radius of our planned 25.5-inch combo on the yardstick and where we expect the tire to tuck inside, we discovered that the EcoNova’s long oval wheelwells allowed for plenty of clearance before rolling inward.

Here’s where it gets a little tricky with the rulers; the first place a tire will make contact during a turn on a subframe-equipped GM car is on the rearward side of the subframe itself. With the discs pointed straight ahead, Kingsland noted where the two intersected, then we slowly turned the steering wheel to full lock and measured how much more backspacing could safely be packaged.

The hub diameter may or may not be an important measurement to have, depending upon the car and the wheels you opt to run. For hub-centric wheels, it’s a much more critical number. For our Nova, we’re more interested in confirming clearance in the wheel.

While it’s not an issue with our stock GM rear drum brakes, the front discs and their hefty hub need to be measured to make sure they’ll fit beneath the center cap. In our case, the 2.8-inch hub height would require a specific centersection for the wheel that has extra depth. Also note the step on the hub; we need the measurement at the fattest point to ensure clearance.

If you need to confirm the bolt circle, the ruler will tell all as well. Simply measure from the center of one stud to the rear of the stud that is almost directly across from it. You can also measure from the center to center on the studs and multiply by 1.05. Either way will get you close enough to make the answer obvious.

Up front, we start with the same clearance measurements to get a baseline. Of course, the front wheels do much more than just roll along like the rears.

Brake templates are downloadable from companies like Baer Brakes if you’d like to be very exact. Here’s how to quickly check whether the wheel you’re considering will clear your intended brake package. Neither diameter nor caliper size will be an issue with our 11-inch discs. If you’re running the good stuff, Boze has special forgings for Baer, Brembo, StopTech, SSBC, CPP, Wilwood, and AP Racing.

For a starting point, Kingsland measured the backspacing on the 15x7 rally that came off the car, since we knew it cleared with no issues. It was 4 inches dead-on.

Here’s what the filled-in Boze spec sheet looks like. These are downloadable from their website.