Hey, I said it was a nerdy observation!
Yup, I've been testing cars with my gear ratio/speed/tire size calculator. Enter the gear ratios and the AT shift point (6600 rpms in this case), take it to the max speed test, and record your speed when it shifts. Then fiddle with tire diameter until the calculated shift speeds match the observed shift speeds. The Grand Sport comes up with 24.86 inches as the tire diameter as the best fit, and the Coupe as 25.25 inches, and the difference is noticeable. With the same stock gearing, the Grand Sport shifts into 3rd at 79mph, and the Coupe at 81mph, for example. Basically the best I can estimate is to within 0.05-0.1 inches and still get the calculations to fit observations, so sometimes I have to guess at the final tire size, but usually there are only a couple options and it's pretty clear what the tire size has to be.
One more observational point confirms the shift point (rpms), I calculate a speed at some fixed rpms in top gear (say 5500) and watch as the needle just hits and passes that point, and record this observed speed, too. I know for sure the tire size has to give a calculation close to this speed, and if it does but doesn't for the shift points, then I know I've guessed the shift point wrong. That's how I know the shift point is 6600 and not 6575 or 6625.
24.86 inch diameter tires could be:
225/55R15 = 24.74 inches, too small, and unlikely that wheel is 15"
225/50R16 = 24.86
205/55R16 = 24.88 inches, certainly common on less sporty cars, but kind of weak for a corvette
225/45R17 = 24.97 inches, would be nice, but too big
25.25 inch diameter tires could be:
actually lots of ridiculous things, like 165/55R18 or 225/80R11, but most likely:
215/60R15 = 25.16, nah too fat and wheel too small for a sports car
235/55R15 = 25.18, again, R15 unlikely, and visually the Coupe and Grand Sport appear to have the same size wheels
195/60R16 = 25.21, too skinny and high profile
235/50R16 = 25.25
295/40R16 = 25.29, sounds like a nice tire for a sports car with 16" wheels, but too different from the Grand Sport to make sense
215/55R16 = 25.31 another possible candidate, except in lap time testing the Coupe was indeed faster, so it's unlikely this would be the correct tire since it's less sporty than a 225/50R16, not more sporty
As a point of trivia, I've worked through the Alfas, Aston Martins, Audis, BMW's, and Chevy's now, and the V8 Vantage has the best tires by far, 285/45R17's, which is also close to what they're supposed to be, 285/45R18's in real life stock. Only rarely did PD give the exact real life tires to GT2's cars, but usually they were very close. The Corvette is the worst deviation by far that I've yet see, since it's supposed to be on 285/40R17's.
Yeah. I guess sometimes I tend to get crazy!
) or Event Synthetizer (90% sureness)
