Wheels and tires make a huge difference in the way a car looks, and they can also make a significant improvement in performance. The wheel drives most of the style, but choosing a traditional 60- or 70-aspect ratio, or a modern 30- or 35-aspect ratio for a shorter sidewall, also affects the look that the wheel and tire give the car. Together, the wheel and tire package should reinforce the image you want. After all, it’s often the only radically changed external component on a classic Chevelle.
This Tech Tip is From the Full Book “CHEVELLE PERFORMANCE PROJECTS: 1964-1972“. For a comprehensive guide on this entire subject you can visit this link:
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Style is completely in the eye of the owner. There are countless styles, from retro to ultra-modern, and you can have the style you want in just about any finish too. It’s also possible to use original-styled wheels, even if you want a brand-new wheel or a custom size and backspacing. Picking the right style can be aggravating, as there is no right or wrong. There are a couple of style items to consider, however. First, what will be exposed with large-diameter, open-design wheels? If you have jumbo disc brakes at all four corners, by all means, show them off with an 18-inch five-spoke wheel. But if you have stock drum brakes on the rear, think about how that will look. What else will be visible behind the wheel? If you haven’t or don’t plan on detailing the undercarriage, choose a wheel style that covers most of the area.
There is an endless discussion about which wheel diameter looks best on a muscle car. Traditionalists never put anything larger than a 15-inch wheel on their Chevelle. But if you want extreme performance brakes, you likely need a 17-inch or larger wheel to clear a large caliper on a big-diameter rotor. Also consider that the amount of tire that can be seen in the wheel well has more to do with how well the wheels and tires fit the car than whether the car wears a 15- or 18-inch wheel. In other words, the lower the car, the better the wheel and tire look. This is critical when you are building a pro-touring car with an 18- or 19-inch wheel. The short sidewall of the low-profile tires doesn’t fit the muscle car proportions of a Chevelle unless you can cover part or all of the sidewall with the wheel opening lip by having the car sit ultra-low.
At the front, a very low car poses issues with steering. You likely need to find a good compromise between the optimum stance for the look you want and a ride height that allows the tire to turn without detrimental rubbing. Unlike a new-car manufacturer, hot rodders are generally okay with a little bit of tire rub as long as it doesn’t destroy the tire or the car, and as long as it doesn’t get much worse as the suspension moves.
At the rear, it’s easier to get the look you want because the tire doesn’t steer. The 1964–1965 cars have a wheel lip that hangs low, giving them a great, extra-low appearance. All of the Chevelles have a rear wheel opening lip making it possible to cover part of the tire sidewall for a pleasing appearance.
The best overall advice I can offer on choosing wheels and tires for appearance is to think about the style of car you’re building and make sure the wheels are consistent with that look. A pro-touring car needs a wheel larger than 16 inches, a traditional car needs a traditional-style wheel.
When it comes to performance, however, there are right and wrong things to do, and there are tools and math to make sure you get what you need. Fitment is the first issue to master. For Chevelles, there are three groups among the models that drive the maximum tire size that fits: 1964– 1965, 1966–1967, and 1968–1972. The older cars are the most restrictive in the wheel openings, with each change in body style providing a little more room for larger tires. During this eight-year run of production, drag racing was becoming extremely popular, and racers quickly learned the advantage of running wider tires on the rear of the car to provide more traction. Since the auto industry was lock-step with racers at that time, the rear wheel wells grew to accept wider tires.
Ten years ago, it would have been possible to rattle off the widest tire size for each of the three body styles, along with the wheel size and dimensions, and feel pretty confident that they would fit. That’s not the case now because of so many variances in the front suspension, as well as the increasing number of people who are switching rear axles and installing rear disc brakes. Each of these things can move the wheel mounting location; and in the front, most suspension modifications change the arc in which the wheel moves as you steer, as well as how the wheel and tire responds as the suspension compresses and rebounds.
People are building their Chevelles with much lower ride heights than ever before, which dramatically affects the maximum tire size you can fit under stock sheet metal.
And then there’s the final factor, which is that a lot of people aren’t leaving wheel wells stock, making room for even larger tires. That’s why instead of a chart with maximum tire sizes, in the project on page 39, I review the steps on how to measure your car with your modifications and at your desired ride height.
Unlike decades ago, tire specifications are more important when building a Chevelle for high performance. If you plan on road racing your car, you very well may see speeds approaching 150 mph, which makes the speed rating of your tires a critical specification. Unfortunately, the traction rating on the tire measures good traction in a variety of weather conditions. To find tires that provide a compromise between street life and on-track traction, talk to other enthusiasts and check forums to learn what people are saying.
Project 1: Wheel and Tire Fitment
Step-1: Check Wheel Clearance
Choosing new wheels and tires for your Chevelle can be quite stressful. It’s easy to spend more than $3,000 on the new combo, and you don’t want to get it wrong. Changing from 15-inch wheels to larger-diameter wheels opens up a new set of tire dimensions to learn and understand. You also want to make sure you’re getting the widest tire possible under the car for optimum performance. Make sure all four current tires have at least 30-psi air pressure, then park the car on smooth, level pavement. Steer from lock to lock and make notes of how much clearance the current wheel and tire combination has to the sheet metal, sway bar, frame rail, and so on. Also measure how high the top center of the wheel opening is off the ground.
Step-2: Remove Wheels and Tires
Next, jack the car up and remove the wheels and tires. You need four short jackstands to return the car to original ride height. This is important so that you’re sure the suspension is compressed just as it was with the tires sitting on the ground. If you don’t have jackstands that are short enough, you can measure from the center of the wheel to the top center of the wheel opening and mimic this measurement, allowing the car to be higher off the ground with the wheels and tires removed. Either way, make sure the car is secure on the jackstands before doing any work on it.
Step-3: Measure Wheels and Tires
With the wheels and tires removed, measure the overall width and diameter of the tires. Laying the tire on the floor and using a framing square as a straight edge on the sidewall helps to get an accurate width measurement. Also, measure the backspacing of the wheel (from the mounting flange to the inside wheel lip) and the overall wheel width. Using all of these measurements, along with your notes about the extra clearance you had with the wheels and tires still mounted, you can estimate the biggest wheels and tires that will fit.
Step-4: Determine Wheel Dimensions and Backspacing
If you want to be more precise in your estimate, you can use a slick tool from Percy’s High Performance called the WheelRite. This tool takes the guess work out of estimating wheel and tire fit by simulating a very wide range of wheel diameters and offsets, as well as tire sizes. It fits four- and five-lug hubs and can simulate a wheel from 15 to 30 inches in diameter. This inexpensive tool can save you a lot of money by helping you determine the correct wheel and tire dimensions the first time. The first step in setting up the tool is to adjust the wheel diameter with the set knob and sliding apparatus (A).
Use the top knob and sliders to set the wheel width and backspacing. For now, set the desired wheel width; you will adjust the tool later to find the optimum backspacing. Bolt the WheelRite to the hub using three lug nuts, tightening them snugly by hand. Make sure the tool sits on the hub flat and square. You may need to remove the brake caliper in order to rotate the tool. Bend the wire to simulate the profile of the tire. You can start with the sidewall height of the tires you removed or the ones you hope to use. You can refine this as you go, so don’t worry about getting it perfect at this point.
Use a tape measure to verify the wheel diameter, tire diameter, wheel width, and tire width. We needed to tweak the wire to get the tire radius to 13¼ inches, which would mimic a 26½-inch-tall tire. Square-off the edges to more accurately represent the transition of the sidewalls of the tire into the flat tread section. One very important note about the WheelRite: It gives you an idea of clearance inside the wheel, but all wheels are shaped differently. You need the brake intrusion info to be sure the wheel fits over the brake caliper and rotor combo you have in mind. The more extreme the brake system, the more difficult it is to find wheels that fit.
Step-5: Determine Tire Clearance
With WheelRite set up with your desired wheel and tire dimension, swing it in an arc and steer the car left to right. The front areas of a Chevelle that it contacts first are the center rear part of the wheel well (shown), the sway bar on the front when turned in the opposite direction, and the center top of the wheel lip if your car doesn’t sit too high. It is very important to note that the measurements must be taken with the suspension and brake package you plan on using already installed. Changing these components can move the mounting flange of the wheel, as well as change the arc that the wheel and tire move through as you steer. You also want to leave enough room to accommodate suspension compression. It’s ideal to make these fitment checks with the suspension spring removed so you can compress the suspension 2 to 3 inches from ride height to simulate what happens to the tire placement when you hit a bump.
Step-6: Determine Wheel Dimensions and Backspacing at Rear
The WheelRite process is much easier at the rear of the car where you don’t have to worry about steering. You can also look for marks from the current tires rubbing the wheel well. While the factory four-link rear suspension makes the rear axle travel straight up and down with very little side-to-side play, nearly all Chevelles have different optimum backspacing from the left side to the right side. This is due to production variances, and I’ve seen them off by as much as 1/4 inch. Pick a tire size and wheel backspacing that leaves adequate clearance on the tighter side of your car. Also, make sure that this backspacing doesn’t push the opposite side into the outer wheel opening lip.
Step-7: Check Brake Caliper Clearance
This car has a set of Baer 14-inch rotors and six-piston calipers, which create quite a bit of intrusion. Basically, the back part of the wheel must be pushed toward the outside edge to clear the brake caliper. Sometimes it is necessary to increase the backspacing by 1/4 inch and run a wheel spacer to provide brake caliper clearance. If you do this, get the wheel spacer from the wheel manufacturer to avoid warranty issues. Another potential clearance problem can arise with the valvestem. It’s now popular to locate the valvestem on the barrel of the wheel behind the center. Big calipers can hit the valvestem, requiring a very short valvestem.
Step-8: Check for Wheel Clearance
Before mounting the tires on your new wheels, mount the wheels on the car and raise the suspension to ride height. Check for clearance issues. At the front, move the steering lock to lock and check all of the clearances. It’s easier to correct potential issues now without the tires mounted.
Step-9: Get Tires Mounted and Balanced
Once you’re satisfied that the wheels fit, and that the tires most likely will too, take them to a good tire shop to have them mounted and balanced. Be sure to quiz the shop about what tools it uses to mount the tires on the wheels, whether it guarantees the work, and what kind of weights it uses for balancing. All of the weights should be stick-on types applied behind the wheel center so they are not visible. Look for a shop that uses tools designed to avoid damaging the wheel lips.
Step-10: Inspect Wheel and Tire Combination
This 1966 Chevelle is fitted with 265/35ZR18 BFGoodrich g-Force T/A KDW front tires on 18 x 9-inch wheels with 5¾ inches of backspacing and 1/4- inch wheel spacers. This combination works with a combination consisting of an ABC Performance suspension system, Baer six-piston calipers on 13-inch rotors, ABC Performance splined sway bar. These tires and wheels work at this ride height, but may not work with other components or at a lower height.
Step-11: Verify Ride Height
I can’t stress enough the impact that ride height has on the tire size that will fit under stock sheet metal and on the appearance of the car. The height of this car looks great, and the wheel lips are right at the top of the wheel openings. This gives the car a very low, aggressive stance. However, this is as far as the front tire can turn before hitting the top of the wheel opening. This car is fitted with QA1 coil-overs, so the ride height was increased one inch by using spanner wrenches to raise the lower spring perch on the coil-over body. The performance and the ability to adjust ride height have made coil-over and air-ride suspensions very popular on pro touring cars.
Written by Cole Quinnell and Posted with Permission of CarTechBooks