Re-Tiring A C5

A Grand Idea--Grand Sport-Spec Tires and Wheels On A C5

Danny Kellermeyer is a retired GM engineer. He is now a full-time Corvette race car builder, part-time race driver, and owns a barnyard full of C4 and C5 race cars. We have always been curious about why he uses '96 Grand Sport wheels on his C5 racers, so we called him at his shop and here is what he said: "When the fixed roof coupe was being developed in 1997 and 1998, John Heinricy did a lot of work testing the package for showroom stock competition. During the testing, John was able to turn faster lap times with the 17-inch front/rear Grand Sport wheels compared to the factory 17-inch front/18-inch rear wheels. John was so impressed with these results that he was able to get the Grand Sport wheels approved for the SCCA T-1 showroom stock category."

Danny continues, "I figured if it worked for John it would work for me, and we won a lot of races with this setup." Danny suggested that we should try this combination for ourselves to determine if we'd see any improvement on a C5 street car. We figured that our '00 fixed roof coupe would be an ideal candidate for this experiment. Danny jumpstarted our project by supplying us with two 17x11-inch Grand Sport rear wheels. We ordered a pair of 17x9.5-inch Grand Sport front wheels and center caps through Mid America Designs'catalog.

Now that we had the car and the wheels, the most important part was tires! The C5 Z06 is the benchmark for Corvette performance, so we decided to seek tires that were as identical as possible to the Goodyear Eagle F1 Supercar tires on the Z06. As luck would have it, Goodyear recently added Eagle F1 SCs in several 17-inch diameter sizes. A quick call got the ball rolling and we soon had a set of P275/40- and P315/35ZR17 tires sitting next to the Pewter fixed roof.

We selected Kauffman Tire Service to mount and balance our new tires and wheels because they utilize the latest Hunter state-of-the-art mounting, balancing and alignment equipment. We were pleased with the final results. The tires were mounted on their rims blemish-free, and they are smooth at any speed. John Taube from Goodyear recommended that the camber be set 1-degree negative to help make the car's response when turning into corners more precise. Kauffman aligned the car per Goodyear's recommendation.

On the road we were immediately impressed with the ride and the lack of tire noise. The alignment change made a dramatic improvement in the way the car attacks a corner. Very little wheel input is required to set the car up for a quick turn. We hit several heavy rainstorms and wet weather traction is excellent. However, with wider tires it is always a good idea to slow down and look for the gray spots on the highway to avoid hydroplaning.

Now on to the final stages of our experiment--how does this setup perform on the track? We contacted Justin Bell, owner of the Justin Bell GT Motorsports Experience Racing School and asked if he was willing to compare our new wheel/tire package to one of his schools Z06 training cars. J.B.utilizes the Z06 to train his students in one-, two- and three-day high-performance driving schools. Justin was delighted to help us out, so we packed up the car and headed off to Moroso Park Raceway in West Palm Beach, Florida, where he conducts many of his schools. Justin is a past FIA GTS driving champion, and he drove the factory C5R Corvette during the 2000 season. He was Trans-Am Rookie of the Year in 2001 and currently drives a Jim Derhaag prepared Trans-Am Corvette. We were delighted to have such a talented driver compare our car to one of his school's Z06s.

After a tire pressure check (32 psi front/33 psi rear) Justin took the car to his wet skid pad. His reaction? "This car has a lot of grip for a non-Z06. The tires are very predictable when they break loose and it was easy for me to regain control in a slide. Overall, I was quite impressed." Well, so far so good. Our next stop was the 10-turn, 2 1/2-mile Moroso Park track. Justin took a school Z06 out for three hot laps and then jumped into our car for a direct comparison. Track and weather conditions were the same, so he would be able to give us some candid feedback. We mounted a g meter in the cabin to note our braking and cornering forces and saw 1.1 gs under hard braking and .98 g in several tight corners. Our car is equipped with Vette Brakes & Products' Coldfire slotted rotors and Hawke HP-plus brake pads. Justin ran the first lap with the active handling on and the next two laps with it switched off. His times improved dramatically with the system off, and the last lap's time was very close to the Z06.

Afterward, Justin told us, "Well, first of all, I know our Z06 very well, so I know exactly how it should handle. I run the car with the active suspension set in the competition mode. But the interesting thing I noticed immediately on the project car is that the tires are wider, lower, have huge grip and the brakes are very impressive. These factors increase the corner entry speed to a fair degree; this means that the mid corner speed also is increased. The net result of this is that your one-setting active handling system is permanently activated. In my opinion, this is because the parameters in which it was designed have been exceeded. I could feel the grip of the car, but I couldn't use it. By deactivating the system, I could then appreciate these tires on this car. It allowed me to roll the car into the corner with a lot more speed off the brakes. It allowed me to maintain on-throttle mid-corner speed, and it really allowed me to come out of the corner with a lot more stability than I am used to in a standard C5. So, I enjoyed the tire, it felt a lot more like a Z06 than other C5s that I have driven. I don't recommend driving with the system off in everyday driving, but in track events like an autocross the car is faster with the system off. So for the person who wants more out of their C5, I highly recommend adding these wheels and tires."

There you have it, from an expert. Danny Kellermeyer's 17-inch Grand Sport wheel combo is a winner on a stock C5, especially with Goodyear's Supercar tires. The next time you need to replace your tires, you might want to hunt around and get some Grand Sport wheels. Then, if you mount a set of these incredible Goodyear Eagle F1 Supercar tires on your C5, go out and have yourself some fun!

9

Danny Kellermeyer races this fixed roof coupe with '96 Grand Sport wheels.

This is our '00 hardtop with factory wheels, and with its new Grand Sport look. Note how the 11-inch wide rear wheels and 315/35 tires fill out the fender.

This is John Heinricy's T-1 development car. Note the ZR-1 wheels.

We recruited Justin Bell, an accomplished driving instructor and road racer, to wring out our '00 Hardtop and offer his professional opinion of the Grand Sport tire and wheel conversion.

Justin tested the car on the school's wet skid pad to determine how the new Eagles handle wet conditions.

Justin ran three hot laps in one of the school's Z06s before lapping in our fixed roof.

Under hard braking, Justin was able to drive deeper into the corners with the active handling turned off. Hard on the throttle at 130 mph, the project car demonstrated a lot of grip on the racetrack.

What About My Tire Pressure Sensors?

Tire pressure sensors are standard equipment on C5s and are an excellent safety feature, especially since the spare tire and jack were eliminated from Corvettes in 1997. When we added the Grand Sport wheels, we decided to leave our sensors on our original wheels. We ordered a new set from GM and gave them to Kauffman Tire to install. They fit perfectly. If you want to keep the sensors on your original wheels like we did, order the following part numbers: For '97-00 you'll need four each of the following: sensor PN 10438853, $126.25 each; retaining nut PN 10268439, $1.88 each; and O-ring washer PN 10268438, $1.88 each. These are the same for all four wheels. In 2001, GM went to an FM bandwidth sensor, with the following part numbers: sensor with O-ring PN 2571358, $80; and retaining nut PN 25708165, $3.68.

After Kauffman installed the new sensors, we discovered they didn't work. So we visited John Wysocki at Maher Chevrolet, and he walked us through the sequence on how to reprogram the sensors. John demonstrated the process by pressing the option button on the dash until you get the English Language message. When that message appears hold the button. With your other hand press the reset button twice and hold it until you get the tire training message on the dash, then release the buttons. Next, get out of the car and hold a magnet over the left front valve stem until the horn sounds once. Repeat the process (LF, RF, RR, LR) for all four tires. Like magic, we now had our tire sensors working. The reprogramming only took about five minutes.

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