It's not the 60 series by itself that's the problem.
The "series" is the sidewall height, but it's listed as the percentage of the width of the tire.
For example, a 245/60/15 means that the tire is 245mm wide, and the sidewall height is 245 x .60 = 147mm. If you want the height, you double the sidewall height, convert to inches, and add the rim diameter.
147x2= 294mm =11.57"
So the tire height is 11.57+15= 26.57"
The width of the tire has just as much of an effect on what will fit as the series does.
On a 5.5" rim you can go as wide as a 215, but it has to be a 70 series. If you're running 14's that's fine, if you have 15" rims then that tire will work on the rear, but not on the front (it's 26.9" tall).
As far as 245/60's on a 5.5" wide wheel, yes, that would be totally wrong, and potentially dangerous. You can usually get by if you're within a 1/2" of the recommended range, but more than that can cause abnormal wear and handling.
