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How to Properly Measure Your Ride for Custom Wheels

Getting It Right

Jim Smart Jun 30, 2017
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Easily the most challenging cosmetic issue facing your car building project is wheel and tire selection, along with proper fitment. Few things are more discouraging than spending a fortune for new wheels and tires only to discover they do not fit, or perhaps they just don’t look right on your vehicle. Wheels that look sharp on a Camaro may not hold water on a Chevelle. Wheel sizing is also critical. Some enthusiasts want as much wheel and tire as they can stuff in a wheelwell. However, sometimes too big is just too big, making your Camaro look like something of a circus wagon instead of a fierce muscle car.

Chris Plump of American Racing is here to set the record straight on how to measure and select a wheel for a perfect fit. Chris says to never to guess, but know exactly what wheel and tire combo is going to fit your Chevy and be user friendly where the rubber meets the road. You shouldn’t go at wheel and tire selection willy-nilly because this is one of the largest investments you’ll make for your car next to engine and driveline upgrades, and perhaps suspension.

The first order of business is wheel size. There’s wheel width and there’s advertised wheel width. A popular misconception according to Chris is the belief advertised wheel width is wheel width. It isn’t. Advertised wheel width is from bead seat to bead seat. The bead seat is where the tire meets the rim. Actual wheel width is from face to face, meaning from the outermost part of the wheel from side to side.

If you order a wheel based on a manufacturer’s specifications of 8.00 inches wide, you’re actually ordering a 9.00-inch wide wheel. In other words, an advertised wheel width of 8.00 inches is actually 9.00 inches wide. If you’re cutting wheel fitment close, ordering an 8.00-inch wheel width could get you into trouble when it’s time for mounting. Another issue is sidewall tire bulge beyond the 9.00-inch actual wheel width.

Backspacing is where wheel fitment and selection gets tricky because everyone has a different interpretation of backspacing and where measurements take place.

Here’s how it is done: Lay a straightedge across the back of the wheel at the lip. Measure from the straightedge to the flange (wheel center and lug holes). This is the wheel’s backspace.

Another hot button item that trips up a lot of us is hub diameter. Take a pair of calipers and measure the hub at its largest point. You want the wheel to fit on the hub nice and snug, but not an interference fit where you feel like you need to force the wheel. The wheel should glide right onto the hub and stay there. Once you have hub diameter sorted out, check hub length. How far does the hub stick out? It has to be able to fit inside the wheel center cap.

The bottom line with wheel fitment is you must know the overall size of a wheelwell by the time you sit down to place an order with American Racing. The vehicle must be sitting at proper ride height when you begin measuring all dimensions. You must also allow for suspension movement, which can be significant as you cruise down the road and encounter the many irregularities. If you’re going road racing or autocrossing there’s another consideration in the measuring process. How much will your suspension move sideways as you cut the apexes?

Getting Started

There are tools of the trade you’re going to need to properly measure a wheelwell for proper wheel and tire fitment. Here’s what you’ll need:

Yardstick (ideally steel)
Tape measure
Fine thread nuts that fit your lug studs (you may also use lug nuts)
Flat washers of the same size

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1. The sheer number of wheel and center combinations at American Racing is stunning because there are so many that can be custom-ordered and made to your backspace and offset in any style you desire.

Wheel Fitment American Racing Camaro 002 3/24

2. Chris Plump at American Racing tells us there is a real difference between advertised wheel width and actual wheel width. Advertised wheel width is from bead seat to bead seat inside the rim. Actual wheel width is from lip to lip, which adds at least 1-inch to the advertised wheel width. Also, keep sidewall bulge (width) in mind, which goes beyond actual width by as much as 1 inch depending upon the tire and inflation.

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3. Wheel diameter is measured from lip to lip across the wheel’s diameter.

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4. Wheelhouse height comes into play as shown from inside the trunk or outside of the wheelhouse. Wheelhouse modifications, such as tubs, will change everything.

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5. Using a yardstick fastened to the brake rotor hub as shown, measure the distance from the hub to the top of the wheelwell. To get an accurate measurement and proper clearance, put vehicle weight on the axle to get true vehicle ride height. Measure from the center of the wheelwell as well as to each side—three measurement points.

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6. Here, Chris Plump measures brake caliper clearance. This can be a slippery slope because there are variations in disc brake packages. You want 0.060-0.100-inch clearance between the wheel and caliper due to thermal expansion of the brake caliper when it is hot. It is strongly suggested you go even greater than 0.100-inch to be safe.

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7. Next, measure from the brake hub with a straightedge to the inside of the wheelwell in front or wheelhouse in back. In this case, we’re talking 10 inches.

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8. We’re measuring from the hub to the brake rotor flange here.

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9. Here’s another way of looking at a wheelhouse. In back, measure with a yardstick/straightedge from the lugs to the top of the wheelhouse at three locations just to make sure you are covered. Make sure you have supported the axle to achieve true vehicle ride height.

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10. When it’s time to build a wheel at American Racing, these wheels are precision-checked for runout, which checks the rim for irregularities.

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11. This is the wheel assembly turntable. These are shims designed to hold the wheel stationary and on spec in the jig.

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12. The wheel is heated as shown to achieve expansion for wheel center installation. The wheel expands, which makes room for installation. The center is positioned and welded.

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13. American Racing can produce nearly any wheel size/center combination imaginable. When you visit American Racing, it’s like being a kid in a toy store. Endless selection with great-looking centers.

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14. Here’s a wheel center along with the corresponding order. Once you’ve established exactly what you want in terms of size and style, American Racing builds the wheel to your order. This is why you must measure the wheelwells in great detail as they relate to the axles and brakes. Before you is the birth of a VF502 wheel.

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15. A custom-ordered wheel center is placed inside the wheel as shown and readied for welding.

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16. The wheel and center are set up in this special jig for welding. Welding is automatic and spot-on perfect.

Wheel Fitment American Racing Camaro 019 20/24

17. Check it out. This precision-welded wheel and center are good to go for our 1969 Camaro project.

Wheel Fitment American Racing Camaro 020 21/24

18. How wide do you want? Here’s a custom wheel born for drag racing.

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19. All American Racing wheels are dynamic balanced for smoothness. When you receive your set, you can know with great confidence the wheels are true and have been balanced.

Wheel Fitment American Racing Camaro 022 23/24

20. Our American Racing VF502 Forged wheels are a perfect fit thanks to Chris Plump’s close attention to detail during the measuring process. Measure thrice, build once. This is where you must take your time and check measurements at least three times and write them down. We stress three times because this is too important to screw up.

Wheel Fitment American Racing Camaro 023 24/24

21. Before you mount tires to the wheels, install the wheels and check the lip-to-chassis clearance to be sure it’s acceptable. In short, check all dimensions when your wheels arrive.

Photos: Steven Rupp


American Racing Custom Wheels
Rancho Dominguez, CA 90221



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