This is probably a dumb question but I have no experience with tires so here goes. We bought my girl friend winter tires P225/75 R15 last year, but she sold her truck and her new one has 16" rims. I know the R15 is for rim size. So does this mean that we are SOL with the tires I have. I am guessing there is no stretch factor. Anyhelp would be appreciated. I dont want to shell out another $600 for tires this winter.