Corvettes were designed to go around curves. Sure, they go fast in a straight line, too, but there are lots of cars—lots of American cars—that do that as well. It's the handling that separates the Vette. Unfortunately for those of us who are enamored of the early cars, neither ever-increasing performance standards nor aging components have been particularly kind to our rides. Having already upgraded the brakes on "Scarlett, our 1972 Chevy Corvette Coupe project car, it was time to go through the suspension, starting with the front. Since the suspension of the Corvette was virtually unchanged from '63 until almost the end of the third generation, all of these modifications apply equally to midyears as well as sharks.
Before we get into the nuts and bolts of things, though, one of the biggest changes you can make in the handling is by changing the wheels and tires, and that's what we did first. Unlike the C2, which has seriously limited room under its bodywork for wide tires, the shark has plenty. Measuring carefully to get the maximum amount of rubber under the car with the minimum amount of interference, I settled on a set of Summit Racing Legend wheels in a 17x9-inch size for the both the front and the rear. They're visually similar to the classic gray-center, five-spoke wheels that appeared on many of the early race Corvettes, making them an excellent aesthetic fit for our '72. And thanks to the addition of a couple inches of wheel diameter—while keeping the outside diameter of the tire about the same—they allowed us to significantly reduce the amount of tire sidewall employed.
Much of what you deal with anytime there's rubber in the suspension is deflection: When things get "loaded," or have force put on them, rubber tends to give. When it's the sidewall of the tire, that deflection changes the radius at which the car negotiates curves. Suppose you're going into a hard right turn: The tire wants to stick the pavement, while the cornering forces on the wheel push against that, to the left. Since the tire is flexible, it doesn't track straight in the direction the car is going, but tends to "walk" toward the outside of the turn, meaning the car travels in a wider radius than you want it to. Reducing the amount of sidewall makes the car track straighter, since there's less sidewall to flex, and it also offers a much more positive feel. The downside, however, is that it makes the car's handling less forgiving, since you have less warning before the tire loses traction and begins to slide.
Obviously, we picked a wider wheel (the factory rims were 15x8 inches) in order to use wider tires, since more rubber on the road means more traction. For Scarlett, we selected BFGoodrich G-Force Sports, again supplied by Summit Racing, in a 275/40-17 size. When you consider that the stock tire was only around 215mm wide, you get the idea of how much larger a contact patch these BFGs create—something like an extra 2.5 inches of tread width. Wide front tires give great bite when you first turn into a corner, but also have a tendency to track changes in the roadway, so you have to pay close attention to keep the car from wandering.
Since unsprung weight is also a key factor in handling, I weighed the factory wheel and tire (I had 245/15s on the factory Rallys) and one of the new ones. Despite being much larger, the new wheel/tire only added about a half-pound to each corner. Not desirable, but an acceptable tradeoff, especially considering that we dropped about 5 pounds of unsprung weight per wheel when we swapped the factory cast-iron brake calipers for aluminum Wilwoods a few issues back.
We added the extra inch of width into the backspacing of the wheel, increasing it from 4 to 5 inches. While no modifications were required to fit the wheel to the front of the car, we did find that when turned all the way in, the tires would rub on the front sway bar and frame. We also had to use stick-on wheel weights located well inside the wheel, instead of clamp-ons at the lip where the wheel meets the tire. There was just barely enough clearance to prevent the steering-rod ends from hitting the wheel itself, but they would have taken clamp-ons right off.
With the wheels in place, before I could tear down the front suspension to start stiffening things up, I had to take some measurements. Adding that much rubber in the front of the car increases the amount of strain on the rest of the suspension components. This includes the shock towers, where the upper suspension pivot is mounted. Under hard cornering, these can flex and, ultimately, break. To ameliorate this problem, we ordered a front "spreader bar" from Van Steel. These consist of a pair of brackets that slip over the bolts holding the upper control arms in place on either side, and are then held in place by the factory nuts. The kit also comes with an adjustable round bar with a Heim joint on either end. Each of the Heim joints is bolted to one of the two brackets, tying them together. Since one of the joints is reverse-threaded into the bar, the bar either gets longer or shorter when it's turned.
There are two bars available: one for cars with electric fans, which needs only to be bolted in place and adjusted, and one for mechanical fans. Since there are so many different pulley and bracket variations, the mechanical-fan version comes with the brackets in three pieces, and will need to be welded together. Predictably, mine has a mechanical fan, so I followed the instructions that came with the kit and slipped the brackets into place on the A-arm bolts, mocking up the L-shaped bracket parts until I found an arrangement that would clear the front fan. With everything measured and scribed in place, I dropped the bar off at North Georgia Machine to be welded and got ready to tear down the front end.
The accompanying photos cover the job in detail. The entire breakdown, including time to get the car up on jack stands, took me about three hours, but it bears mention that I had the advantage of having done it before. If you haven't, I suggest using the Van Steel instructional video. It greatly simplifies the process compared to, say, the Haynes manual, which still leaves me mystified about what to actually do. (It does, however, contain the critical torque values for reassembly.)
Unfortunately, you're only half done. You've still got the rear to go…
Check out the rest of the series in Part 2 and Part 3 of the Sure-Footed Shark!