I am looking to replace my present rims with an aluminum style. According to the catalogs the rim sizes start at 14x6 and the originals are 14x5.5. I currently have Chevy rally rims of an unknown width. I can put my fingers between the sidewall and fender at this time and am concerned about clearance. Can you tell rim size by the tire size? Is there an offset necessary for proper clearance? Thanks, Mark