Chevy Chevelle Bolt-on Suspension Performance Test - Find The Handle

On the skid pad with the stock suspension, the car leans horribly due to the weak springs and minuscule sway bar. The subliminal message is the port-o-potty in the background.

On the skid pad with the stock suspension, the car leans horribly due to the weak springs

Performance Evaluations
We have to spend some time with the results chart so it is not misleading. If we only look at the peak slalom speeds, the peaks appear to suggest that the new suspension parts produced little or no improvement. That's why we included the average numbers. While the peak numbers lend some insight into what the suspension and/or tires are capable of producing, the average numbers reveal much more. Overall, we saw a significant improvement in average speed on the slalom of just over 1 mph with the addition of the sway bars and shocks, but a better indicator was the increase in average speed when the 17-inch tires and wheels were added to the suspension in Test 4.

The best way to learn more from these numbers is to subtract the average speeds from the best speeds to evaluate how difficult the car was to drive. It makes sense that the closer the average speed is to the peak, the easier the car is to drive. Conversely, the wider the gap between the two numbers, the harder the car is to drive. Using this evaluation, the old suspension with the 17-inch tires (Test 2) reveals a massive discrepancy of 3.05 mph (44.62 - 41.57 = 3.05 mph), while the smallest difference between peak and average was with the new suspension with the 17-inch tires (44.62 - 43.93 = 0.69 mph). So while Licata was able to bang out a great time with the 17-inch tires on the old suspension, it was a hero effort that he was not able to replicate in five other attempts. On average, he was much smoother and the car was far easier to drive with the Bilstein shocks and Addco sway bars along with the 17-inch General tires. This is no big surprise, but the numbers do tell an interesting story.

Bolting on the General UHP tires led to a hefty improvement, with the modified suspension pulling a best of a 0.83 g on the skid pad. It was much easier to drive near the limit on the slalom with the large sway bar, shocks, and 17s, but it still exhibited moderate to severe understeer on corner entry. Despite this, the Chevelle was still a solid 2.5-plus-mph faster in the simple 400-foot slalom.

Bolting on the General UHP tires led to a hefty improvement, with the modified suspension

Skip pad testing must also be carefully evaluated. While we recorded a slight improvement in the lateral traction, the results were less than impressive because the majority of the increase came from the better tires. You can see this just by comparing the gain in Test 2 with Test 4. The explanation is also relatively simple: By design, the skid pad tests the suspension once it is completely loaded. That means this is really a test of suspension geometry, springs, and tire adhesion with virtually no input from the shocks. Since the springs are still stock and extremely soft, it's no surprise there were minimal gains.

Our '65 Chevelle may be long in the tooth, but it can still hang in the corners with the more exotic modified muscle cars. This Chevelle can pull a full g average on the skid pad with DOT-legal 18-inch rubber.

Our '65 Chevelle may be long in the tooth, but it can still hang in the corners with the m

The Next Level
If you've been reading Car Craft for a while, it should be no surprise that we've been beating on Chevelles to improve handling for many years. Along the way, we've learned much about what works and what doesn't. Condensing all this information would probably demand a book, but let's see how far we can get. In the front suspension, the limitation is the Chevelle's very short spindle height. As the body rolls, the stock geometry allows the loaded tire (the left front in a hard righthand turn, for example) to roll the top of the tire outward. This results in a major gain in positive camber-the exact opposite of what you would prefer the camber to do. The simple fix is to use monster-stiff springs in the front to limit body roll along with adding a couple of degrees of negative camber so when the body does roll, the positive camber gain will retain some negative camber to plant the loaded tire. But for a street car, all that negative camber is undesirable because it kills the inside edge of the front tires very quickly.

Many years ago, A-body suspension pioneers discovered that taller, '70-'81 Camaro or B-body (big-car) spindles bolt in place and radically alter the camber curve, so as the body rolls in a turn, negative camber actually increases allowing the suspension tuner to use street-friendly camber alignment settings. This eventually led to companies like Global West and Hotchkis building bolt-on tubular upper control arms that allow you to take full advantage of these taller spindles. A combination of calibrated front spring rates, tall front spindles, a pair of tubular upper control arms, and the proper sway bar will transform the front suspension in these cars.

Until recently, our Chevelle package consisted of stiff front springs, a 1 1/8-inch front bar, tall B-body spindles, Global West upper and lower front control arms, and single-adjustable shocks. In the rear, we were using very soft rear springs with no sway bar and single-adjustable shocks. It's that simple-and it works.

Until recently, our Chevelle package consisted of stiff front springs, a 1 1/8-inch front

That is exactly what we did with our '65 Chevelle several years ago and (with some minor changes) is the combination we used on it for the Run to the Coast event ("Pro Touring Shootout," Aug. '10). It's been a while since we tested the Chevelle on the skid pad, but with good tires, the car is capable of generating 1.0-plus g numbers. It also requires tubular upper and lower control arms in the rear and the elimination of the rear sway bar combined with a very soft spring rate. Of course, these performance numbers are assisted by big 275/40R17 or 275/35R18 sticky tires mounted on 17- or 18x9 1/2-inch wheels with 6 inches of backspacing front and rear. And yes, that tire and wheel package will fit under a '64-'67 Chevelle with very minor outer wheel lip trimming. We won't mislead you-generating this level of handling requires serious suspension tuning. But it is more time-consuming than difficult. The promising thing is that it can all be accomplished with a stock frame and stock suspension pickup points. If we can do it, you can, too.