I have a 2093 Chevy S10. I want bigger rims, and a set of 18" rims came available. Before I spend 500+, will they fit, or would I have to alter the wheel well, etc.??

Wow what does a 2093 look like? Is it a 2003? the truck was made to hold a size of rims and tires that will function without issues. The bigger you go, the less room you have under the fenders.The over all height is what you need to look for along with the width. 15" rims with the tall side wall tires may be the same as the 18" with the skinny sidewall tires so that is not an issue. the width is the next concern. You go wild, you will rub and cut a tire or wrinkle a fender, so make sure it will fit. you may need a lift kit or fender flairs if you go overboard.

Width, back spacing, lug pattern are more important as far as fitment than just the rim size. It is possible to put 18's under it, the other factors matter more, and if your truck is a 4x4 or 2wd