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Discussion Starter #1
I politely ask that responses be limited to personal experience and not conjecture. I have been looking at aftermarket monoblock forged wheels. There is no problem having one made to the OEM wheel diameter and width. The problem is offset. The C7 Z51 OEM wheel specification is front (19x8.5 +56) and rear (20x10 +79). Typical monoblock forged wheels can only be machined up to +50 for the front and +70 for the rear. This 6mm and 9mm difference doesn’t seem like much. My question is does anyone have personal experience how a smaller offset affects C7 handling since it changes the scrub radius? Can you specify what offset you have? Can you comment on 45 mph and 65 mph cornering? Did you experience any feel difference from the OEM setup when the steering response becomes stiffer switching from tour-sport-track modes? Even a response that no difference was felt would be appreciated and would help me in my decision. Also, I would rather not use a spacer.
 

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No specific Vette experience here, but I have (on other cars) modified offsets and spacers resulting in far greater differences than you are contemplating. I haven't found those changes detrimental in any way, but were usually accompanied by other suspension mods. Most all Aftermarket wheels for the Vette have different offsets and spacing. Trust Glen above. He's been through 2 sets from different manufacturers that fall into that category.
 

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Discussion Starter #5
Thank you for the feedback. I have been following Glen’s build thread over the last several months as he went from the TRW Nurburgring to Cray wheels and appreciate his comment that he could not detect any difference due to an offset change. I downloaded the following SAE publication on suspension design:

http://users.telenet.be/AudiR8/Mechanical Engineering - SAE - The Automotive Chassis OCR.pdf

This led me to the following calculation. The OEM offset is +56mm. Several aftermarket single piece forged wheels are made to +50mm. This is a difference of 6mm. Thus, the center point of the tire on the road surface is 6mm from the OEM position. The camber adjustment tolerance is +/- 0.6 degrees or a total angle of 1.2 degrees. The tire radius is 12.9 inches or 328mm. The position of the tire on the road surface can vary by 328 x tan(1.2) = 6.87mm and be within the camber tolerance setting. Since the offset change of 6mm is less than this, handling should not be affected. I think! I’m open to critique.
 

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I would argue that the calculation should be done only for 0.6 degrees instead of 1.2 degrees. The tolerance due to camber is +/- 3.4 mm from nominal. We cannot assume the camber tolerance puts us in the range of +6.87mm to -0. The offset of the tire is +6 mm, which is outside the +/- 3.4 mm range.

However, I am sure none of us would actually notice in real life.
 
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