[JohnWR]

All 20s (or 19s or 18s) are not the same, as a lot depends on the outside diameter of the tire. If you are trying to match the OD, going from an 18 to a 19 or a 20 will make major changes, but if you are also changing the OD, going from an 18 to a 20 may not be a big deal.

 

[JohnWR]

Unfortunately (as i am sure most are aware) there just isn't that much outer diameter to play with, especially in the rear wheel wells unless one is willing to modify the fender well liners, which i don't even know if thats is doable or worthwhile.

i would happily consider lowering it with adjustable coil-overs and just get wider rims in 18 diameter but lowering it around here is a bad idea…

My post was aimed toward @ChopTop 's comment about the large wheels on a Silverado, and how the tires must be really special for a wheel that big.

I parked next to a C8 Corvette on Saturday and was surprised that the front tires are 245/35-19. I didn't think to look at the rears.

 

[JohnWR]

Stiffer is not always better for tires or for suspension, unless you are on a glass-smooth surface. For the tires to grip they have to stay in contact with the road, and if things are too stiff any bump will upset the contact patch enough to cause serious problems.

 

[JohnWR]

I have read your comments on many of these types of threads and appreciate the mention of unsprung weight.
that thinking was part of my decision to go with the TCE Wilwoods as they shaved 11lbs off each front wheel. Maybe a bigger deal than any increased stopping power from the upgrade.
My question would be, if you remove unsprung weight “just” from the front of the car (as in my case) will that negatively affect the overall suspension?
I am self admittedly uneducated on this topic and would love to hear some real world feedback.

Unsprung weight reduces road holding over bumps. Reducing it only in the front may result in increased oversteer when encountering rough pavement in a curve. In situations where the whole car would shift slightly sideways over a bump or series of bumps, you may experience the rest shifting more than the front.

 

[JohnWR]

If you believe that installing wheels that are larger than stock is wrong, than I'd think you might want to consider replacing your heavy OEM 18 wheels and tires with some 13X6 inch alloy rims & six inch wide tires.

I'm sure the Kappa wheel weights have been posted before, but even the OEM wheels & tires are far from light. Plus the Kappa 18 inch wheels were considered quite large for the times. I'm not positive by I don't think anything larger than 20s were available back in 06.

Plus had the Kappa continued it wouldn't surprise me to see that they would have offered 19s or 20s wheel packages.

No one has said that larger wheels are "wrong", just that they are unlikely to improve performance in most cases, and are actually more likely to decrease it. Unsprung weight is not the only consideration, or really even the primary one with a car as heavy as the Solstice. The perspective on unsprung weight has generally been that adding to it is counter-productive unless the addition results from something that provides a greater performance improvement in another way.

13 x 6 may be a bit extreme, and going to extremes in either direction is somewhat ridiculous, but I think that most people, in most real-world conditions, would benefit from something like a 245/50-17.

Larger wheels would certainly have been offered as time went on, but that doesn't mean that the goal would have been better performance, just as ir likely wasn't in 2005 with the 18s on the Solstice. Style and public perception are major components of car sales (fake vents, anyone?) and the things that attract attention and push sales are going to be offered regardless of their actual performance value.

What is "correct" really depends on your goals and perceptions, so what works for you may not work for me and vice-versa.