Normal ..it is the diff gearing on them.

But , some guys run 215/75/14 on the stock rims ..that gives you a 2" diam difference [ from 24.7 to 26.7]
The 255/50/16 will only give you a difference of1.3" and you will have to buy 16" rims besides..plus I think they are too fat for the chassis.

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A Dalton