C5 Corvette Sway Bars - Sway, Sway, Go Away

Testing Hotchkis' New C5 Anti-Sway, Er, Anti-Roll Bars

Team Vette Apr 1, 2000 0 Comment(s)
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Let's clear up something right now: Nearly everyone refers to them as "sway bars" or "anti-sway bars," and those bars at both ends of every C5 Corvette most certainly are neither. A "sway bar" would be there to make the car sway, and an "anti-sway bar" would be a device to control or eliminate sway. If we're going to be correct about our terminology, at least as it relates to what the products do, let's call them "anti-roll bars," because their purpose is to control a car's roll (or lean) in corners and turns. Now, with that out of the way...

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When Chevrolet developed the C5 Corvette, the engineers did a marvelous job of crafting a car that would both ride and handle impressively, unlike the bone-jarring ride of early C4s with the Z-51 suspension option. But for serious enthusiast drivers of '97-99 C5s, even Z-51-equipped cars can benefit from stiffer bars. The Corvette engineering staff belatedly recognized this and has fitted heftier front and rear anti-roll bars in 2000 Corvettes with the Z-51 underpinnings.

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Shortly after the C5's debut as a 1997 model, GM's Chevrolet Race Shop began developing a fifth-generation Corvette suspension system for use in SCCA club racing. This system, known as the T1 Suspension Package, is now sold by GM Performance Parts. The need for stiffer anti-roll bars as part of the package led Chevrolet Race Shop's Ken Brown to call on John Hotchkis of Hotchkis Performance with a request that Hotchkis and Race Shop work together to develop a library of larger outside diameter (OD) bars with varying wall thicknesses

The tight confines of the computer-designed C5 suspension presented the first challenge. Any major increase in the bars' outside diameters caused clearance problems if the bars were bent in the factory configuration. While the engineers at Hotchkis developed new bend "schedules," Race Shop's R&D crew designed new, stiffer and larger-diameter frame bushings.

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Ultimately, with the aid of a computer, nine different stiffer anti-roll bar combinations were selected, and several sets of 90-durometer, polyester-filament-lined rubber frame mounting bushings were molded for final testing for the T1 kit. Testing showed that the C5's stock molded-plastic end links for the anti-roll bars weren't strong enough to handle the added stress, so the Race Shop specified Teflon lined spherical bearing end links, which survived severe testing at Daytona and Sebring without a hitch. The tests showed that an extremely stiff set of bars was required when used with the T1 kit's special springs, shocks, and A-arm relocation bracketry. The selected front bar measures 1.5 inches outside diameter with a .250-inch wall thickness, which makes it roughly 200-percent stiffer than a '97-99 Z-51 front bar. The T1 rear bar is 1.062 OD with a .209-inch wall thickness, and is approximately 100-percent stiffer than a '97-99 Z-51 rear bar

Using what they learned from the T1 anti-roll bar development project, Hotchkis began developing a street-friendly, but decidably "sporty," set of bars for everyday driver C5s. Tests run on a 600-foot slalom allowed Hotchkis to finalize outside diameters of 1.25 inches for the front and 1.00 inch in the rear, but more testing was necessary to fine-tune the wall thicknesses. Fun or not, you can't run serious, high-speed handling tests on a local canyon road or sweeping freeway onramps or interchange connectors. Pure and simple, and whether you're worried about getting tickets or don't care, testing on public thoroughfares is too dangerous.

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Then, Lady Luck smiled. Scott Gillman, Product Development Manager at Hotchkis, was observing T1 suspension testing at Buttonwillow Raceway in central California and spent a few minutes between sessions talking with Chevy's test driver, Rupert Bragg-Smith. Scott mentioned that he'd been unable to find an adequate test site and a supply of C5s to use for his final development work. Rupert's response was, "Come out to my school in Pahrump (editor's note: in Nevada, about 60 miles west-northwest of Las Vegas. See "School Daze" on page 28 of this issue for more about the Bragg-Smith school) and you can test during my off season. We have 10 '99 C5 and a private 2.2 mile, 10-turn road course."




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