HI
As long as you can find one (a wheel) the well fit you lug pattern and over your hubs then yes you can.. Just remember that going to a different size tire is going to throw you speedometer off by a few mph. It well read like 30 mph but you well only be going around 25 mph. depending on how much difference there is in the overall size of the tires. Say your 16"ers are 31" tall if you go to a 15" tire that is 31" tall then you'd be ok no change in you speedometer. but if the 15"ers are like 29" or 31" tall you'd have a problem with you speedometer not reading right.
good luck
tim