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How to Measure Your C2 Corvette for Proper Tire and Wheel Fitment

Fine Fitment: Dialing In the Tire and Wheel Fitment on a Midyear Corvette

Tommy Lee Byrd Mar 2, 2017 0 Comment(s)
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Every car guy on the planet has been at a car show and spotted a car that just doesn’t have the right tire and wheel combination. Maybe the tires are too small, the backspacing is wrong, or the look just doesn’t jibe with the car’s personality. Whatever the case may be, tire and wheel choice is crucial if you want your car to turn heads for all the right reasons. Our beloved C1 and C2 Corvettes feature classic lines and unmatched appeal, but even these timeless creations are subject to tire and wheel fitment issues. Chevrolet didn’t leave much room to operate in until the 1968 model year when the slightly wider C3 body provided a little more real estate for tires and wheels. For this installment, we’re focusing on the C2 generation, specifically the drum brake cars of 1963 and 1964.

Even seasoned Corvette guys classify the 1963-’67 model years as being interchangeable when it comes to overall chassis dimensions. After all, the frame is the same and the body measures the same. However, when Chevrolet added disc brakes to the Corvette in 1965, it increased the car’s track width, a maneuver that was beneficial for the driving experience but tricky for tire and wheel fitment. So, if you’re dealing with a 1965-’67 Corvette, know that the factory disc brakes push your tires and wheels 3/4 inch closer to the wheel opening than the drum brake cars. If you are upgrading your 1963-’64 Corvette to disc brakes you’ll need to take that into consideration as your current tire and wheel combination will likely interfere with the body. Zero offset rotors can be sourced but most affordable brake kits feature the factory-style one-piece rotors that add 3/4-inch per side.

The confusion escalates even further when dealing with a modified car, as a lowered ride height can cause fitment issues and aggressive suspension alignment for autocross racing may also create problems. It isn’t cut and dry, and what works for one Corvette may not work for another, so follow along as we measure and modify a drum-brake-equipped 1964 Corvette coupe for two new sets of tires and wheels from the folks at Coker Tire, Rocket Racing Wheels and Newstalgia Wheel. The Tennessee-based companies specialize in tires and wheels for collector vehicles of all shapes and sizes so we knew we could rely on the staff to steer us in the right direction. We took all of the measurements and gave them the results, hoping for two off-the-shelf combinations that would showcase two period-correct looks for our old hot rod.

We quickly figured out that the rear of the car was the most difficult to measure and the most troublesome when it came to interference points. The 1963 and 1964 cars with drum brakes have less than 4 inches of room between the wheel mounting surface and the leaf spring, meaning that 3 3/4 inches of backspacing is the maximum allowance. This measurement increases by 3/4 inch when using disc brakes (4 1/2-inch maximum backspacing), but then the wheel’s front side spacing becomes the problem on disc brake cars. If you’re leaning in the Pro Touring direction, the good news is that some 18-inch wheels clear the leaf spring, and then you can install offset trailing arms to gain a little more room. Also consider that the 1965-’67 cars have an emergency brake cable bracket on the side of the original trailing arm, so those brackets will need to be relocated for additional room.

With all of these findings, it’s no wonder that everyone slapped a set of fender flares on these cars in the ’70s. Owners couldn’t find a reasonable wheel to fit so they added to the body to compensate for big tires and wheels. With the rising value of midyear Corvettes, we doubt that you’ll resort to fender flares to fix your tire and wheel fitment issues, so take a look at our measurements and guidelines to fit the most tire and wheel possible beneath your stock-fendered C2 without bumping into that precious fiberglass body.

Guidelines for 1963 and 1964 Corvettes with Drum Brakes

Front Tire Diameter: 25 to 27 inches
Front Tire Section Width: Up to 8 1/2 inches
Front Wheel Width: 6 inches is comfortable (7 inches may rub in hard cornering)
Front Wheel Backspacing: Up to 3 3/4 inches (tire-to -frame clearance)
Rear Tire Diameter: 26 to 29 inches
Rear Tire Section Width: 10 1/2 inches (with modified bumpstop)
Rear Wheel Width: Up to 7 inches
Rear Wheel Backspacing: 3 3/4-inches maximum (wheel-to-leaf spring clearance)

Guidelines for 1965-’67 Corvettes with Disc Brakes (includes 1963 and 1964 with disc brake conversion)

Front Tire Diameter: 25 to 27 inches
Front Tire Section Width: Up to 8 1/2 inches
Front Wheel Width: 6 inches is comfortable (7 inches may rub in hard cornering)
Front Wheel Backspacing: Up to 4 1/2 inches
Rear Tire Diameter: 26 to 29 inches
Rear Tire Section Width: 10 1/2 inches
Rear Wheel Width: Up to 7 inches
Rear Wheel Backspacing: 4 1/2 inches maximum

1964 Corvette Drum Brake Wheel Fitment 2/23

01. We’ll start with the simplest measurement, but it is one area of confusion. It’s common knowledge that the advertised rim width is measured at the bead seat, but for the purpose of stuffing the maximum tire and wheel package under your car, you need to know the overall width. This 15x7 wheel measure 7 7/8 inches.

1964 Corvette Wheel Measure 3/23

02. While advertised diameter and width is measured at the bead seat, backspacing is measured at the outermost surface of the rim. That means the extra 7/8-inch of overall rim width is tacked onto your front side spacing. In this case, we’re working with a 15x7 wheel with 3 3/4 inches of backspacing. Quick math tells you that you’re dealing with 3 1/4 inches of front side spacing, but the actual measurement is 4 1/8 inches.

1964 Corvette Drum Brake Wheel Fitment 4/23

03. When measuring for tire and wheel fitment, it is important to keep the car as close as possible to ride height. For the front, you can place the jack beneath the lower control arm and remove the wheel. Note that we’re dealing with a drum brake car (1963 and 1964 only), which has a narrower track width than the later-model disc brake cars. Always measure both sides and compare your notes.

1964 Corvette Drum Brake Wheel Fitment 5/23

04. Our first measurement is from the mounting surface of the wheel to the wheelhouse lip. We used a long straightedge against the wheel mounting surface and a short straightedge to measure the distance to the wheelhouse lip. We come up with 5 inches, but keep in mind that disc brakes move that measurement 3/4 inch closer to the wheelhouse lip.

1964 Corvette Drum Brake Wheel Fitment 6/23

05. The nearest backspacing limiting factor is the steering arm. This arm is 4 5/8 inches from the mounting surface. Even though a wheel with 4 1/2 inches of backspacing would physically bolt on, tire clearance would be an issue when the wheels are turned.

1964 Corvette Drum Brake Wheel Fitment 7/23

06. We crank the wheels hard left and measure the distance from the wheel mounting surface to the wheelhouse lip. The trick here is to estimate your overall tire diameter. Then, you can measure from the center of your hub to the virtual end of the tire to see where it might come in contact with the body.

1964 Corvette Drum Brake Wheel Fitment 8/23

07. We also measure the distance from the mounting surface to the framerail. The front side has 6 inches of room, which shouldn’t be a problem. Caster and camber settings can alter these measurements, so be sure to have your suspension aligned before final measurements are taken.

1964 Corvette Drum Brake Wheel Fitment 9/23

08. Now, we turn the wheels hard right and take measurements from the wheel mounting surface to the framerail. Our measurement shows only 2 5/8 inches of room with a 26-inch tall tire, but that doesn’t account for the radius of the tire, which would gain us approximately 1 inch of real estate. You can safely run 3 3/4 inches of backspacing with a 26-inch tall tire.

1964 Corvette Drum Brake Wheel Fitment 10/23

09. Moving to the rear, we jack the car from the center, then remove both rear wheels. Place one jack stand under the driver-side framerail and another jack stand beneath the passenger-side strut rod. Then jack the driver-side suspension from the end of the strut rod where it meets the spindle upright and shock mount. Push down on the car to ensure the suspension is at ride height, as this greatly alters your measurements.

1964 Corvette Car Jack 11/23

10. Before we get too carried away, we want to see our maximum tire diameter allowance. It looks like we can run up to a 29-inch tire without any major interference.

1964 Corvette Drum Brake Wheel Fitment 12/23

11. The 1963 and 1964 Corvettes feature a bumpstop bracket that can be a major limiting factor for tire fitment. With the bracket in place, we’re looking at 5 3/8 inches from the wheel mounting surface to the edge of the bracket. Unless you’re running a large-diameter wheel, this usually isn’t the nearest interference point, but it does pose a problem for “fat” tires with a lot of sidewall bulge.

1964 Corvette Bumpstop Brackets 13/23

12. If you’re serious about fitting a fat tire under your early C2, then you’ll need to grind the bumpstop brackets until they are flush with the framerail. This gains a little over 1 inch of clearance.

1964 Corvette Drum Brake Wheel Fitment 14/23

13. With the protruding portion of the bumpstop filed away, we’re looking at 6 3/4 inches between the wheel mounting flange and the framerail.

1963 1964 Corvette Drum Brake Wheel Fitment 15/23

14. The number one limiting factor for backspacing on drum brake cars is the leaf spring. Our measurements show 3 15/16 inches between the wheel mounting surface and the edge of the leaf spring. Of course, you could clearance the bushing, cups and the edge of the spring to gain a little more. Comfortable backspacing for the rear would be 3 3/4 inches.

1964 Corvette Drum Brake Wheel Fitment 16/23

15. If you’re running an 18-inch or larger rear wheel, you will likely clear the leaf spring, which means you can run more than 3 3/4 inches of backspacing. The next area of concern would be the trailing arm, which only offers about 4 5/8 inches of room. Offset trailing arms are available to help accommodate a deeper backspacing.

1964 Corvette Drum Brake Wheel Fitment 17/23

16. The next area of concern is tire clearance, and as you can see, this car has encountered some slight rubbing on the trailing arm. For our maximum allowed tire diameter of 29 inches, we’re looking at 5 3/4 inches of real estate, but the sidewall bulge is the real problem area. Always account for at least 1 inch of sidewall bulge when using a common 15-inch tire and wheel combination.

1964 Corvette Drum Brake Wheel Fitment 18/23

17. Finally, we can carefully clamp our long straight edge to the quarter-panel and take an overall measurement of the wheelwell. With the bumpstop clearanced, we have 11 inches between the framerail and the quarter-panel lip, which has been trimmed. This tells us that 10 inches of section width is the maximum allowance for a car that does not have trimmed lips.

1964 Corvette Drum Brake Wheel Fitment 19/23

18. We determined that the ideal rear wheel configuration for an early (drum brake) C2 is a 15x7 wheel with 3 3/4 inches of backspacing. This stays clear of the suspension components on the inside, and perfectly aligns with the wheel opening.

1964 Chevrolet Corvette Rear Side 20/23

19. The 1964 Corvette coupe used for our testing is an old-school hot rod, with mostly stock suspension. It has been lowered 2 inches in the front with drop springs, but it should also be noted that extreme changes in the ride height makes a big difference in tire and wheel fitment. Tire fitment was a large part of the fender flare craze in the 1970’s.

1964 Chevrolet Corvette Front 21/23

20. Combination one is a classic look for an early Vette, but we gave it a little bit of drag racing influence. The wheels are American Torq-Thrust D from Newstalgia Wheel, sized at 15x4.5 up front with 2 1/8 inches of backspacing with Coker Classic 165R15 tires. The rears are 15x7 with 3 3/4 inches of backspacing, mounting BFGoodrich 235/75R15 tires, also from Coker.

1964 Chevrolet Corvette Front 22/23

21. Combination two is a collection of Coker Tire and Rocket Racing Wheel products that give the car a menacing street racer look. The 15x4.5 Rocket Strike wheels feature an as-cast finish and 1 3/4-inch backspacing, and mount to Firestone 5.60-15 bias-ply tires. Coker Tire offers a full line of M&H Racemaster tires, and we opted for the Vintage series slicks in 9.00-15 sizing, mounted to 15x6 O.E. steel wheels with 3 3/4 inches of backspacing.

1964 Chevrolet Corvette Front Wheel 23/23

22. Rocket offers the Strike wheel in several 15-inch configurations, as well as in newly released 17-inch fitments. We opted for the skinny front-runner to go with this car’s angry attitude. If you’ve ever tried to put slicks on a C2, then you know that finding a tall and narrow profile is tough. The M&H 9.00-15’s measure 10.30 inches wide and 29.30 inches tall.

Sources

Coker Tire
Chattanooga, TN 37402
866-516-3215
www.cokertire.com
Rocket Racing Wheels
Chattanooga, TN 37406
888-307-7525
RocketRacingWheels.com
Newstalgia Wheel
800-281-2819
www.newstalgiawheel.com

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