This is a thermal image of the Viper’s four tires after a skid pad run by Doug Milliken. There appears to be a lot of weight transfer going on here due to the lack of cornering contribution and heat generated by the inside (left) tires, so the outer (right) tires are doing most of the work. This is not ideal but the Viper’s massive tires are still able to pull some pretty high cornering Gs. The Viper has very little static camber with the factory specs of -0.2*Front and -0.5*Rear (+/- 0.2*) and it appears to have very little camber gain due to the excessive heat and wear on the outer shoulder of both front and rear tires. Since the tires are not being loaded evenly, adding some static negative camber will greatly improve the cornering ability of the car by taking the load off the shoulder and using more of the inside of the tire. Photo source: Road & Track 6/1999
After the track day, our 275/35-18 front tire wear is consistent with the thermal images. The outer shoulder was worn down completely due to the tire rolling over on itself and focusing the load and temperature (in red) on the outer shoulder. It appears we need an additional -1* to -2* of static front camber for more even tire loading and wear, which will greatly increase our front grip.*An interesting note, the Viper has shims in between the upper control arms and the chassis. Removing the shims add -1* of camber without affecting the alignment. I think it’s great that the Dodge engineers added this to the Viper since it’s a method found in many race cars to adjust camber. When at the track; simply pull the tire off, loosen the two bolts, remove the shims and tighten them back down. That’s it. A simple and easy way to get better on-track performance in the matter of minutes. Since the thermal images and many magazine tests never removed these shims to add camber, we wanted to test the characteristics of the car in the same stock form before improving it.
The Gen-3 sized 345/30-19 rear tire also shows similar wear to the thermal images, focusing the load on the outer shoulder of the tire as it rolls over on itself in a corner. Due to the rear tire’s massive footprint and since they are the driven wheels, it does not need as much static negative camber as the fronts. An additional 0.3* to -0.8* should suffice to better distribute the load across the tire and start using more of the inner part of the tire to give us more rear cornering grip and power-down exit grip.
DATA
We had a Motec C125 Dash in the car to record our laps. Now let’s analyze some data:
This is the entire “Pace Lap” from the video above. As you can see in most of the corners the Viper sustained around 1.0 G even though it was a very easy lap and the car was not pushed very hard. Around the 0:25 second mark we can see Turn 4 which shows the G-forces around 1.0 G despite drifting the corner. At the 1:10 second mark on the back straight, there was a lift off the throttle and light braking well before Turn 9.
