Up until a few years ago, the Z51 package was a hot ticket on the sixth-generation Corvette. While it lacked the visual impact of the Z06 or ZR1 body, among other things it came with a no-frills, performance suspension with higher rate springs, shocks and larger sway bars (some of which were shared with the Z06). But of course, times change and after the LS2 was replaced with the LS3, Chevrolet decided it was time to replace the Z51 package with the Grand Sport–better bridging the gap between the Z06 and the base Corvette. The Grand Sport received not only the wide-body treatment, but the wider and stickier wheel/tire package that came along with it. The addition of the larger Z06 brakes only reasserted the Grand Sport's dominance over its predecessor. So what is the owner of a 2005 Z51 to do?
In the case of this particular owner, I decided to call Pfadt Racing about its new Johnny O'Connell Signature shocks and sway bar package. As many of you know, Johnny is a four-time Le Mans winner and ALMS Corvette Racing driver, and he worked closely with Pfadt to develop this package to marry "racecar level road holding ability" and "streetability you would expect from a daily driver." Considering the usage of this car, as a daily driver, I couldn't have picked a better setup. Pfadt says in developing the suspension, O'Connell compared several versions and revisions on the "race track, mountain passes and pot-hole riddled roads." They even have a slick video with Johnny discussing the suspension and of the testing (http://bit.ly/x3O6dh). For those of you wondering, this suspension is also a great upgrade for a base Corvette, Grand Sport, or Z06 as well.
Though the revised dampening capabilities and reduced body roll of Pfadt's Level I Suspension would potentially increase cornering grip, there really is no replacement for displacement–or contact patch. So first thing was first, we'd need a wheel that would allow a larger tire, especially in the front–to help prevent the all-too-familiar front-end plow (aka understeer). And since our Johnny O suspension was a recession-friendly $1,000; it didn't make sense to spend three times that on custom wheels, which we didn't have (by the way). Thankfully SLP Performance Parts had the perfect solution, a set of ZR1-style wheels (18x9.5 front, 19x11 rear) with an offset for the base Corvette body that would allow for Grand Sport and Z06 size tires. For $900 we had ourselves a great looking set of wheels that fit the overall theme of our build, and would allow for more substantial meats. A win, win. Speaking of rubber, we liked the stock sized Nitto Invo tires so much, we decided to stick with them except in 275/35/18 and 325/30/19 (courtesy of Discount Tire). If nothing else, this would give us a very accurate A/B comparison of the difference between a larger and smaller contact patch (using the same compound and tread design). The Invo has the added benefit of being fairly grippy while extremely quiet and wearing well, perfect for a daily driver.
With all of the pieces set in place, and my office filled with parts, there was only one thing left–a quality installer. Thankfully Greg Lovell at AntiVenom, a Pfadt dealer, was more than happy to accompany us to Gainesville Raceway to swap the suspension track-side to get an accurate A/B comparison. Prior to the install, though, we had AntiVenom drop the C6 as far down as it would go on the stock bolts, and then have the car aligned at a local shop. Using this plan we figured to gain some significant ground on the Grand Sport, even without its fancy big brakes and dry-sump LS3.