Ride and Handling Revisions
We can’t close out the ’02 Z06 story without talking to another of my Corvette pals, Mike Neal, the C5 ride-and-handling Lead Engineer who’s directly responsible for much of how C5s feel when we drive them hard.
"There were two concerns with more torque and horsepower," Neal told us just before deadline. "How do we 1): put that down to the ground and 2) can we, also, improve ride comfort?
"We addressed both those the same way. We improved the ’01 rear shock valving to eliminate some of the choppiness you feel on certain road surfaces. That, also, improved ride.
"At start-of-production, we were happy with the ’01
valving. Later, there was an occasional street driving situation where we said, ‘Gee, this is a little bit more choppy than we’d like to see.’ We saw this as an opportunity for ’02. At the same time, we had more torque coming. We’re always asking, ‘What can I do to get this thing to hook-up better when I plant my foot on the gas pedal?’ "
The lexicon of ride-and-handling is filled with words development engineers use to quantify ride motions in discrete ranges. A "choppy" surface is not one causing large, slow suspension movements, such as running over a swale or a dip, nor does it cause small, rapid movements, such as crossing a ripple strip. Choppiness is kind of in between those two types of ride motions. A choppy road will impart a medium velocity to the suspension.
"On roads with chop in them," Mike Neal continued, "the (’01) car is so tied down; it was reading all that chop. If you can feel chop in your stomach, then the rear tire can ‘feel’ it, too, and that’s a load condition change. You don’t want that. You want to have that loading as smooth as possible so you get the power down and the tire doesn’t unload and begin to spin.
"With the ’02 shock valving, the changes were in the mid-velocity range. We trimmed that down to reduce the abrupt, chopping motion. You trade away body control when you do that, but we got body control back by increasing the damping in the low-velocity shock range.
"The upshot of all of this is you get both smoother, vertical loading of the rear tires when you go to put power down exiting a corner and you get a ride comfort improvement–definitely a win-win."
The competitive driver will feel revised shock valving the most in autocrosses which are typically run on parking lots which can have rough, choppy road surfaces. Mike Neal’s work on the ’02 will make it easier to apply power exiting turns. Images: Jim
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I mentioned at the top of the story the three hairpins that are Glendora Mountain Road’s first challenge to the sporting driver. Coming off these three in first gear gave me a chance to really feel Neal’s work in controlling the rear suspension. As the intent of the change was to reduce the effects of chop, you’d first think it wouldn’t make a difference on a flat surface like most road race tracks, however, in talking with Mike Neal, I learned that’s not the case.
During transient periods, when the body is actually rolling while entering and exiting turns, the shock
valving, because it resists body motion, is part of the car’s roll stiffness. Dialing back the mid-velocity shock valving slightly decreases the rear shocks’ contribution to roll stiffness in transients. That decrease makes the car oversteer just a tiny bit less and that helps in getting power down upon exiting turns.
Where the revised rear shocks have a stronger effect, because of the changes in transient rear roll stiffness combined with better control of chop, is in autocrosses on rough parking lots. Of course, the new valving will certainly have a positive impact on aggressive street driving. It even makes the car a little nicer riding in every-day driving situations. Mike Neal says it’s a ‘win-win’ and he’s absolutely right.
The only other change to the Z06 suspension is the replacement of the steel, front and rear stabilizer bar links, introduced in 2000 on Z51s and used in ’01 on Z51s and Z06es, with aluminum links. This was done to reduce weight and causes no change in performance.
The other place you’ll feel the difference with the ’02 rear shocks is on drives like an obscenely fast run up
GMR. As you go to roll-on the power exiting a turn, you find the car more stable. Image:
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Final Words from the Chief
In our interview with Dave Hill, the C5 Registry On-Line and Newsletter asked about rumors of the Z06’s demise at the end of 2002.
"We have no reason to discontinue the Z06. There is a definite extreme performance enthusaist segment of the Corvette market that wants a car like that. I think we have struck a responsive chord. We were only able to make about 16% (of production as Z06es) in 2001. We would have liked to have made 20% but we were constrained by wheel availability. We have solved the wheel issue. We are going to up our volume to 20%
and we may see above that.
"I see the Z06 as a permanent part of the Corvette family and increasingly distinct from the coupe and convertible. We’ve done the right thing by limiting it to the fixed-roof-coupe. Not having a lot of
free-chioice gave us the ability to make the best performance car we can make. There’s a very enthusiastic following for the Z06 and those people are buying the car. They got the message. They like the trade-offs that we’ve made on their behalf.
"So we’re going to keep it as the pure performance model. We see the Z06 being with us, even past the platform change-over to C6."
The next obvious question was 2003.
"We’re not going to fuel speculation on the 50th Anniversary," Hill said expectedly, "because we’re still pulling on technology of the C6 that will be brought into the C5. We don’t know if we can get it done in time.
"The 50th Anniversary will be a very special car–a landmark in our lifetime. We’ve got Chevrolet working on some really outstanding celebration plans and product engineering working on a very memorable, very collectible, very significant vehicle. That’s as much as I can say at this point."
Hill addressed one of his favorite subjects: the value in C5.
"We’ve worked every available overtime hour in Bowling Green for five model years to try and meet the demand for Corvettes. We’ve never had to put an incentive on the car to sell it. With today’s competitive marketplace where there is a lot of incentivizing going on–BMW has had to do a lot–I’m proud of that accomplishment as a business man.
"When the car comes ready for trade-in, the C5 value has held up wonderfully. There isn’t an import we compete against that has a better residual retention than Corvette. That’s good for the dealers and our customers. It’s good for the reputation of the brand, too.
"The Z06 was a vision. Now, we’ve stepped back and said, ‘Wow! This car is really awesome!’ It doesn’t surprise me that it’s awesome, but it is rewarding that we were able to do that good and exceed people’s expectations of how well the car performs and how affordable it is. That was one of the things about the ZR1 that just never worked. It was too much price for the car that it was. The Z06 is a hell of a lot more car than you would expect to get for the price.
"That’s what I feel really proud of as Corvette Chief Engineer–that we deliver better value than anybody else out there."