I just returned from a 1800 mile road trip. That with another 650 miles in town gives me a total of over 2400 miles with the Hankook Ventus V12's 245/40-18 on stock SS rims. No indications of rubbing anywhere on the tires on the inside or out. IMHO these tires are fantastic...I can't believe the difference from the Michelins.

 

I would think that a wider footprint would increase the rolling resistance and reduce MPG.

With the wider 245s did you see a reduction in MPG?

 

I'll be looking soon and I think I'm digging the Goodyear Eagle GT's based on:
Price
Made in Ohio
Ultra performance All Season.
Looks good.

 

What is the width of the stock SS 18" rim?

I have after market Drag rims that are 7.5" wide and I am concerned with the wider 245 tire not fitting properly on my 18"x7.5" rim.

GM Parts direct shows the stock SS 18 Alloy Rim to be 7" wide. (see link) http://www.trademotion.com/partlocat...layCatalogid=0

The CONTINENTAL ExtremeContact DWS 245 40ZR18 93Y has an approved rim witdth of 8-9.5 inches.
http://www.tiresdirect.net/CONTINENT..._P5364C930.cfm

 

HHR SS factory rims are 18" x 7.5" wide, http://www.finishlinewheels.com/CHEV...08/A-05336U85/

& the 245 would be better suited on a wider rim, it will fit on a wheel 8.0-9.5", but prefers a 8.5" wide wheel

 

The inside of the wheel is stamped 18 x 7.5. The Hankook has a .6" wider tread which I think is 7%. According to the DIC I averaged 73.6 mph and 28.6 mpg.

 

Just over 3600 miles on the Hankooks. No rubbing and they are great in the rain.

 

UPSIDE:
Hankook makes a great performance tire. You plug in a set and you add 0.2g cornering force. They work well in the rain, and they don't fade when you heat them up (like doing autocross or a track day), and they are relatively inexpensive.
DOWNSIDE:
The tires do not stand up well to any physical abuse. Bump a curb and they might chunk or blister. Skid and they are seriously flat spotted. They also don't go for mileage (although that could be because they inspire "spirited" driving), I put some on the wifes van and they only lasted about 22K miles.
CONCLUSION:
I put a set on spare rims for the 'vette and use them for track days only. Works out really good for performance. If you are willing to sacrifice longevity for performance, buy some. If you want a reasonable performance tire and long life, go with the Firestone Indy 500's, another great value but for a different reason.