I have a 2001 s 10, I also have a set of 15x7 rally wheels , I want a smaller tire on the front and a large as I can get for the rear. What size tire will fit?

Go to your locale tire dealer, decide what kind of tire you want, the tire dealers we have here also carry aftermarket rims and they can tell you what will fit. Going to a larger tire on the rear will affect the accuracy of you speedometer.

I had 18x9 rims on my 99 S10. I sold the truck a couple of years ago, so I have to do the tire size by memory, but I'm pretty sure I had 235x40R18 in front and 245x45R18 for the read. I had also dropped it 3" in the front by spindles and the rear was spacers. I was running BOSS rims and because of the offset on the rim I had to use 1' spacers between the hub and the rim. It did clear.