Are these tires too tall for the Grand Prix? I know the width is correct, but not too sure about the height?

Thanks.

yes a little bit but you may be fine.

I think for 20's it'd be 245/35/20. I'd have to check the miatagarage calculator to say exactly how big but off hand I know they are bigger than stock.

just checked. they are 1" bigger in diameter than stock. So you'll have .5" less wheel gap but you'll also sit .5" higher. you're speedo will be a little bit off. you're biggest issue may be rubbing the fenderwell if you are lowered or the offset is a little off.

If I had to guess tho I would say you'll be fine.

bigwheels.net shows a max tire height of 692mm...the 245/40/20 is listed as 702mm tall

gonna be too much I think unless you roll and flare fenders or are ready for some scraping.