So had some great offline discussions with some folks and wanted to post thoughts on this.
One of the things I was thinking about is that overall diameter is only going to impact the speedo, which most of us don't care about. BUT the ratio of front to back diameter needs to remain as close as possible to stock so the system can operate as intended. The stabilitrack system won't necessarily know/care how fast you're going, but it will know if the tires are spinning at different rates than intended.
If this is true, I assume Chevy considered this, and that the SS 1LE tires are the correct ratio to not cause any issues. But when I did a quick calculation, it doesn't appear to be too close. One of the replies I got from Alpha1BC (feel free to post your feedback as replies - it was helpful to me, but didn't want to take the liberty of quoting a PM) was that the allowable ratio is pretty wide, but he was going to see if he could track down the actuals.
Here are my rudimentary calculations, including some alternate options I am considering for tire sizes.
Stock SS
Size; Diameter; tread width
Front;245/40-20; 27.7; 9.6"
Rear;275/35-20; 27.6; 10.8"
Diameter Ratio: 0.99638
SS 1LE
Size; Diameter; tread width
Front ;85/30-20; 26.7; 11.2"
Rear;305/30-20; 27.2; 12"
Diameter Ratio: 1.01872 (within 2.2% of stock)
Alternate size 1:
Size; Diameter; tread width
Front ;265/35-20; 27.3; 10.4"
Rear; 305/30-20: 27.2; 12"
Diameter Ratio: 0.99633 (within 0.005% of stock)
Alternate Size 2:
Size; Diameter; tread width
Front; 275/35-20;27.6; 10.8"
Rear: 305/30-20;27.2; 12"
Diameter Ratio: 0.985507246 (within 1.1% of stock)
Alternate 1 gets the closest to stock diameter ratio (nearly a perfect match), but alternative 1 is almost an inch narrower, while Alternate 2 is second closest and keeps the front width closer to the 1LE. Do you think I am on to anything here for the folks who don't want to do a tune? My wife often says I overthink things, but as a biochemist and Project Manager, it is part of my DNA
