What Size Wheels Do I Need?

[Kisner]

Well apparently I screwed up again (not the 1st and surely won't be the last). 4 years ago I bought a set of repro 14" x 6" styled steel wheels from Mustangs Unlimited. They went on with no problem. Yesterday I decided to have them re-balanced and rotated. When GoodYear rotated them the 2 that were on the back were hitting my front disc brake calipers when the wheels turned. Apparently the welds on the 2-piece design were higher on the back two. GoodYear, along with a few other friends, are now telling me I should have never put 14" rims on a car with front disc brakes, and that I have to use a minimum of 15" rims? Can someone tell me if this is true? Seems to me Mustangs Unlimited should have asked if I had disc brakes, but they didn't and there was no mention of the wheels not working on cars equipped with disc brakes in their catalog.

If I do switch to 15" rims, would that solve my problem? Also, I need some info on backspacing issues, i.e., what's the largest tire I can used on the 15's without rubbing or hitting something else. I'm running 215/70/14's right now and like the look. Not looking to put anything bigger (tire height wise or width) on the 15's, but would put 60's if they'll fit with no problems. Thanks for any advice.