I've been thinking of replacing my re92's but I want to keep the stock wheels for now, could I fit a 215 or a 225 on the stock wheels with no problems?

 

225s will fit.

Check the exact tire that you want for this though as the manufacturers rate what width is needed for each tire.

Watch out though as it gives it a bulge and might affect the sidewall stiffness for cornering.

 

What would happen if you were to corner too hard with the 225s?