I just stopped by a tire shop because i needed a spare tire I am running 315/75/r16's on my 2003 f150 2wd he had a spare
Will that size tire fit on a spare tire rim that the truck came with? its a 16 but it seemed kind of small

 

Yes, it will. I have one mounted myself. However, some aftermarket and custom exhaust can interfere with fitting a 35 inch spare.