C6, Naked and Exposed:  Corvette Action Center's First Look at the 2005 Corvette - Page 6 of 6

---

C6, Naked and Exposed:  Corvette Action Center's First Look at the 2005 Corvette - Page 6 of 6

by Hib Halverson
©2004 Corvette Action Center
No use without permission

Chassis, Suspension and Brakes - Continued from Page 5...

All C6es, regardless of suspension level, handle better and are just a bit easier to drive at the limit due to Goodyear's and GM's efforts at better run-flat tires, a slight increase in roll stiffness and changes in shock valving.

What should the sporting C6 driver expect to feel in comparison to a C5? We asked Mike Neal that. "More cornering power...that's the biggest thing," Neal said. "And the second thing is more of what I call combination traction, which is, on the friction circle, both lateral and tractive grip. So, as you're powering out of a corner, you're not as quick to loose traction in the rear. The back stays hooked-up better."

Currently, there are two levels of C6 suspension, FE1 and FE3, and two sublevels of shock absorber choices at the FE1 level, base and F55 (Magnetic Selective Ride Control or "MR"). This year, the proper marketing term for base/FE1 is "Corvette Standard Suspension" and the proper term for FE3, which is part of the Z51 package, is "Corvette Sport Suspension". In our interview with Mike Neal, we learned that while basic MR design and operation is unchanged from C5, the system has been revised for C6 with longer shocks, to go with the increased ride travel, different calibration and a new, Siemens controller. For a detailed discussion of MR, see another article at 2003 Corvette: Technical Article: Magnetic Ride - Star Wars Meets the 50th Car.

Z51's Sport Suspension uses larger, 45mm diameter, fixed valve, Sachs shocks vs 36mm, fixed-valve Sachs units for the Standard Suspension without F55. It also uses higher rate springs and stabilizer bars of slightly larger diameter than did C5 Z51. The big news is the Sport Suspension now comes with a specific, higher-performance tire. With the improvement in casing design gaining some handling for the Standard Suspension, for FE3, Goodyear went a measure farther and combined some of the technology in the '01-'04 Z06's F1 Supercar non-run-flat tire with the third generation EMT architecture and came up with a F1 Supercar EMT. It has an asymmetrical tread and some tire compounding differences which add-up to a slight measure better handling compared to the F1 EMT used for FE1. GM claims the new, 2005 Corvette Z51 handles, brakes and accelerates such that its overall performance is just a slight measure less than what a 2004 Z06 can achieve. Again, we'll reserve final judgment until we road test a car but, if that's true, we bet there's going to more than a few Z06es traded for '05 Z51s.

The brakes on base and F55 C6es are similar to those on C5s but there were changes mostly to address the problem with brake rotor durability some C5s had. In fact, for GM, the single most costly warranty issue with C5 was brakes. Base C6 rotors are the same diameter and thickness (12.8x1.26-in, front and 12.0x1.0-in, rear) as those on a C5, but they are more massive, weighing about 2 lbs. more per rotor, and their internal vents have been redesigned for improved cooling. Z51s get, new, larger rotors (13.4x1.26-in and 13.0x1.0-in) which should not affect stopping power appreciably, but will improve fade resistance under race track conditions.

Some Performance Projections

While we have yet to test a 2005-that opportunity will not at the car's "second" press preview to be held this coming May-we're going to guess that the first characteristic a sporting driver will notice about a C6 compared to a C5 is that the car performs just a bit better but achieves that better performance in a more refined and quieter manner.

Considering the C6 Z51 manual's weight (probably around 3200 lbs), that it has the '01-'04 Z06 transmission ratios, that it has 50 more horsepower and it's got better tires on the back, we'll say it should do the quarter in 12.6 at 115 mph.. What about on a road course? Dave Hill has said, "If the Z06 was four-seconds-a-lap faster than a base C5 (on an unidentified race track), the new Z51 takes back three of those seconds" Chevrolet claims that, on a skid pad, a C6 Z51 is capable of over 0.95g. Even the base car does very well on the skid pad at .92g. Again, we'll reserve our own opinion until we drive the car, but if that Neal and Hill say is true then the C6 Z51 oughta be a hell of a ride. As for top speed? Well--my fellow Zroners will kill me for this-but the party's over, people. After 15 years, the ZR-1 is no longer the fastest production Corvette. With its LS2 putting out 400hp@6000 rpm (compared to the LT5's 375hp or 405hp@5800rpm) and a .28 coefficient of aerodynamic drag, a 2005 Corvette targa with a manual transmission will go 180 mph and perhaps even a little faster.

Welcome to Cee-freaking-six, people!

As of February 23, 2004, the Corvette Action Center has developed some accurate intelligence on C6 performance. At GM's Proving Grounds, development testing has resulted in a 2005 Z51 Targa going 0-60 in 4.2-sec. and a base Targa doing it in 4.3-sec. The quarter mile performance of the Z51 was 12.6-sec at 115 mph and observed top speed was 186 mph.

We hope you enjoyed Corvette Action Center's look at the 2005 Corvette. The author would like to thank Dave Roman and Dave Caldwell of GM Communications, Mike Neal of Team Corvette, Tom Read of GM Powertrain and Bill Groak of the L.A. Auto Show for special assistance in producing this article.