what is max i can put on this car and function properly

At least dubs.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Define function properly... these aren't sports cars and if you put biggo tires on them they'll end up steering like crap. Plus you'll be putting some more wear on your axles and suspension components. I wouldn't go much higher than 1 or 2 inches extra wheel diameter from stock.

I am generalizing btw. There are well made wheels that are designed to be light weight. I have seen some 17 inch wheels that are lighter than the MB 14" bundts alloys. That is not a bad way to go as you can actually end up reducing unsprung weight. The cheap crap I see on sale at tire shops though are usually ridiculously heavy.

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1985 CA 300D Turbo , 213K mi