During development, using Z06s with prototype, ’02 LS6 engines, there were a few clutch failures. The extra 15 lb/ft. torque put enough additional stress on the clutch that GMPT decided to upgrade the pressure plate. Clamp load was increased seven percent. This was accomplished by a change in the self-adjusting system inside the pressure plate. The result is an increase in clutch pressure from 2315 lbs. to 2475 lbs. There is also an increase in pedal effort that was deemed acceptable for a high-performance application such as the Z06.
The ’02 LS6’s additional torque output also had the potential to "bottom-out" the damper springs in the clutch driven-disc during clutch action. Damper spring rate was increased by 1.5 pound-feet per degree and a higher quality steel wire is used. Lastly, the disc flange plate (or hub) thickness was increased by twenty percent, from 5 mm to 6 mm.
The head-up display (HUD), introduced for 1999, is popular with C5 owners–so popular that, since its introduction, sales have been 25-40% higher than expected. Even with that popularity, the Corvette development team has been divided on whether or not a HUD belongs on a car like the Z06 and, in ’01, it wasn’t available. Customer input forced a change.
"It was not unanimous," Dave Hill told us. "There was a faction that felt, ‘We don’t like the reflections from the HUD frame.’ and ‘This is not something you need to make a high performance car.’
"Another faction said, ‘Anytime you can communicate information to the driver with no-eyes-off-the-road time, that’s a driving skill enabler–it’s a driving safety enabler.’
"So, it was dead-even. We wanted the Z06 to have relatively few free-expression choices, so, in ’01, we decided to error on the side of affordability.
"The customer input flipped us over. Customers said, ‘If you’re making a driver’s car, why wouldn’t want to use it? We really request that you do that.’
"We had some little mass offsets here and there that could pay for it. It was clear Z06es were seen as more than affordable for what the customer was getting. The HUD is a driver’s aid. We have a HUD that’s the envy of the industry. The customers are asking for it. We decided to make the HUD standard on Z06 for ’02.
New/Old Wheels and the (Almost Not) New Brake Pads
The ’02 Z06 wheels are a tiny bit lighter and made by a different supplier using a new process but they carry over the "old" look. Speedline, the Italian company that does the magnesium wheels (RPO N73) to be discontinued at the end of this year, is the new supplier. Speedline is an industry leader in a manufacturing process called "cast-spun" and the new/old wheels are cast-spun aluminum alloy rather than the forged aluminum used in MY01.
The change in source and process was driven by 2001 Z06 production being restricted because of a wheel shortage. The conversion was planned and implemented under pressure from the shortage but it was impossible to ensure the change would come right at the model year break. Because GM was desperate for Z06 wheels, the decision was to keep the appearance consistent. That way, whenever the new/old wheel came available, the break-point would be transparent to the customer and there would be no problem with cataloging different wheel designs in the same model year. As it turned out, the switch will come at the model change.
Speedline’s cast-spun technology and the history of C5 wheel processes are interesting stories related to us by Dave Hill. "In 2000, we went with forged wheels. We wanted more toughness for potholes, underinflated tires or really hard driving where you might strike something hard enough to damage the rim and have an air loss. There could be gradual air loss due to rim damage with the old pressure-cast wheels we had in the beginning of the C5 lifetime.
"A forging offered a chance to make the wheel tougher, so when we made that appearance change in 2000, it was done with a forged wheel. It, also, gave us an opportunity to make an upgraded, polished wheel that was almost as shiny as chrome, was better looking than chrome and didn’t have all of the environmental problems chrome has. So, forged was the hot set-up in the 2000 model year.
"Basically, the center section (of the ’02 wheel) is a casting. They take that, spin it and work the material out to the rim so it’s more like a wrought wheel at the outer circumference. This technology gives the center section better shape flexibility–which we can use for styling reasons or to reduce mass–but on the rim, it gives you the a crystal structure having the toughness of a forged wheel without being an actual forging.
"We like this because we can get better throughput, which we need to be able to build more Z06es, and we’ve been able to take some mass out. A set of Z06 wheels is .7 kilos (1.5 lbs) lighter than 2001 forged wheels. That’s a tiny amount of mass, but it’s in the right direction. In 2002, the painted (base) wheels and the Z06 wheel will use this cast-spun technology. It really is the next, new technology that’s the best for making a Corvette wheel.
"As for the appearance of the new wheel, the customer probably can’t tell. On the back side of the spokes there is some undercutting that makes the wheel lighter but you can’t easily see that. For all practical purposes, they’re interchangeable."
GM has been developing a higher performance front brake pad for C5s. Last year, this resulted in an aftermarket pad (PN 12480154) made by Hawk Performance and sold through the Corvette Racing Parts program. The Hawk pad may even have been considered for production but the Corvette development team eventually decided not to use them and continued their search.
Challenges in developing high-performance brake pads for production applications are: noise, dust and rotor durability. It is difficult to have a performance brake pad that stops better than a standard brake pad but also is as quiet as, doesn’t emit more dust than or wears rotors as little as a standard pad. Brake pads on performance cars are a customer complaint generator, mainly from noise and dust but also, to a lesser extent, rotor life. The trick was to come up with a pad that had stopping power and fade resistance better than the regular C5 unit but with minimal impact to customer satisfaction issues.
For MY02, Z06es and all Corvettes built for export get a new brake pad with improved fade resistance in aggressive driving situations. One of my old friends on the Corvette Development Team is brake engineer, Jack Gillies. He said that, compared to the base front pad, the new pads are more linear in braking as they get hot and offer slightly more deceleration for a given pedal effort. Gillies stated that the new pad’s braking in normal driving is not much different than the base pad. We don’t think owners of cars not equipped with the ’02 pad who upgrade will feel any change in braking unless they drive their Corvettes very hard.
The new pad was an off-again, on-again prospect. In April, GM announced them in preliminary, ’02 information. During the media preview in early May, Dave Hill backed off, saying the new pad would not make production. Five weeks later, in a news release the day this article was posted at C5 Registry On-Line, GM reversed itself, again, saying the new brake pad would be offered. The decision came so late that the prototype Z06 I tried on Glendora Mountain Road was not equipped with them.
GM’s release says these new pads have better life in performance driving situations than many other pads. It also says that users may notice the slight increase in noise and a slight decrease in brake rotor life typical of any high-performance brake pad.
As with specialized Corvettes of the past, there are going to be a few who will buy a Z06 but never drive the it in the manner for which it’s designed. Some of these owners, especially those doing car shows, might be more sensitive to brake squeaks and dust. We think the best thing for them to do is not expect GM to replace brake pads that are performing as intended, but to retrofit the car with a set of base-level Corvette brake pads then "donate" the fast-guy, ’02 pads to a fellow Registry member drives hard on a regular basis.
"Electron Blue is one of the special colors she did for us. The Nassau Blue, in spite of seeming to be a real classic Corvette color, surprised us with low penetration. Navy Blue is very classical, very sophisticated looking on Corvette but it’s kinda too dark. Electron Blue is between Nassau and Navy. It’s vibrant, but it’s rich. The response at the Museum–at the Birthday Bash–to Electron Blue was excellent. Helen’s got more good stuff coming that will make the Corvette even more eye-appealing. We’re really glad she’s such a enthusiastic Corvette supporter.