On my '97 Explorer XLT, I have Goodyear Wrangler RT/S (P235/75R15) tires w/ 15x7 rims. I wanted to get new rims without getting new tires. I was wondering if I could get rims that are around 15x7 but would still fit, like 15x8 or 16x7. Or do I have to get exactly 15x7? Also, what is bolt pattern and backspacing and how would I find them out? Thanks for all the help.