Much like wiring, measuring for proper wheel fitment and tire fitment is considered a stressful adventure in the automotive hobby. It’s nothing for most enthusiasts to bolt on some performance go-fast bits, or even weld up an exhaust system, but when it comes to figuring out what wheel dimensions will work (or that aforementioned wiring) all bets are off and the second guessing starts in earnest.
Sure, some will throw a spare wheel that is lying around the shop on the car and check fitment, or even borrow a wheel from a friend. Still others will ask total strangers on social media what “should” fit and hope they’re correct. Why not take the stress and inaccurate guesswork out of your wheel fitment and tire fitment with our new WheelWise™ wheel fitment tool on your next project?
Confirming your wheel specs, including backspacing and offset, to order new or custom wheels can be accomplished in no time with our WheelWise™ wheel backspacing tool. Simply assemble the WheelWise™ wheel fitment calculator tool extensions inside the tire you plan to run and secure the sidewall clamps. Bolt the hub mounting plate to the extensions and you’re ready to mount your tire and take some measurements with our WheelWise™ wheel offset tool! It’s that easy!
Our WheelWise™ wheel fitment tool is made from 10-gauge steel and laser etched with pertinent measurement points. Our wheel offset tool is much sturdier than plastic models that have been on the market (that don’t use an actual tire) and is a much better value than the cast aluminum models as well, with precise wheel bolt pattern mounting options in all major five-lug bolt patterns using 1/2-inch studs, plus 5x4.75 with 7/16-inch studs. These specific wheel bolt patterns and stud hole sizes create a much more accurate mounting versus universal slots that inject slop into your fitment check.
Everything you need is included in the WheelWise™ wheel fitment tool kit to measure for 14 to 22 inch wheel diameters from 7 to 17 inches wide! Just supply the front and rear tire sizes you will be using, assemble and mount the wheel measurement tool with tire secured to your axle flange or front hub. Once secured with at least two wheel lug nuts you can check for frame and suspension clearance by cycling your suspension up and down with a floor jack (unbolting or removing your shocks/coilovers may make this easier). Turning your front wheels from lock-to-lock will confirm steering angle changes will not create tire to frame/sheetmetal interference as well. Easily loosen the wing nuts and adjust the wheel measure tool backspacing for optimal tire clearance and then lock the adjustment down. Remove the WheelWise™ wheel backspacing tool and measure your final backspacing needs to order your new or custom wheels.
We have launched additional lug pattern mounting plates to expand the WheelWise™ tool’s ability to test fit tire combinations onto just about anything. From modern trucks to cars and imports, our additional lug plates will help you with just about any vehicle’s wheel fitment needs. No other wheel and tire simulator offers you more flexibility and durability for the value than our WheelWise™ wheel fitment tool.
SpecsWheel offset and backspace are two of the most misunderstood wheel terms, but they are at the center (no pun intended) of your wheel measurement needs to ensure your custom wheels fit your application. Our new wheel fitment simulator helps immensely, but you still must do some basic math. The wheel simulator tool verifies a specific tire size and placement, and then you take some final measurements from this tire measure tool and input them into some basic math formulas (see our Installation Tips section).
First, let’s provide a few quick definitions here to help you:
Overall Wheel Width: This is the total width outside of the wheel lip flange, usually 1-inch wider than the inside “stated width” wheel lip measurement the tire seats. This is measured without a tire mounted using a ruler or measuring tape across the wheel and is expressed in inches.
Wheel Centerline: This is the overall wheel width measurement divided by 2 to halve the dimension, giving us the true centerline dimension of the wheel, expressed in inches.
Backspace: This is simply the distance from the wheel mounting face (where it sits on your brake rotor or drum) to the rear outside wheel lip flange. This is measured using a straight edge across the back of the wheel (without a tire mounted helps) and a ruler or measuring tape from the mounting face to the straight edge and is also expressed in inches.
Offset: This is the measurement between the wheel mounting face and the centerline of the wheel’s width. This one is a little harder to measure, especially on wheels that are solid or have small window openings between the spokes, and confusing enough to some it is expressed in millimeters that can be either a positive or negative dimension.
Installation TipsOffset is the hardest wheel measurement to determine, so using the two easier to obtain dimensions of overall wheel width and backspace we can then determine the wheel’s offset. This is helpful even when using our wheel fitment simulator tool.
Let's use a 10-inch overall wheel width. This makes our wheel centerline dimension to be 5 inches (10 divided by 2= 5). Let's say our tool's backspacing shows a measurement of 5-3/4-inches. At this point we’ve taken two simple measurements and we have everything we need to calculate offset with some simple math.
Formula: Backspace – wheel centerline = offset
Any fractional answer (the 3/4 in the backspace) needs to be converted to a decimal equivalent by division first.
3 divided by 4 = .750
Our wheel sample:
5.750 – 5 = .750-inch
However, since offset is stated in millimeters, we have one more calculation to run. There are 25.4 millimeters in an inch, so multiply your answer from your first formula by 25.4 to obtain your offset in millimeters.
.750 x 25.4 = 19.05mm positive offset (wheel mounting surface towards the outside of the wheel)
If the backspace measurement is smaller than the wheel centerline measurement your offset would be negative (wheel mounting surface towards the inside of the wheel).
Specs Material Type Steel Sold in Quantity Each Finish Bare Material Thickness 0.135 Notes Supports SAE 5-lug wheel bolt patterns, does not support 4-lug, 5-lug metric or 6/8-lug vehicles MFG. Part # 91603280 Tech Support We're here to help before and after your purchase. If you have a question or need assistance with one of our products, please contact us through eBay Messaging and a knowledgeable Speedway Motors team member will be happy to help. About Speedway Motors is America’s Oldest Speed Shop® and has been a trusted source for specialty rodding and racing products and friendly expert advice for more than 72 years. Founded in 1952 by “Speedy” Bill Smith – a racer and street rodder himself – Speedway has grown from a one-man operation to become the world’s largest manufacturer, distributor and retailer of street rod and racing products. Our industry-leading fast delivery is the result of same-day shipping from our state-of-the-art, centrally located 500,000 sq. ft. headquarters. Speedway’s size offers customers unmatched product selection and low pricing, while our excellent technical support and customer service have made us a recognized leader in the rodding and racing industries.