Tires: Switch ML430 from 275/55R17 to 255/55R18, ml430, rim width

Question
HI,
I am looking to switch my ML430 2000 model from wheels 275/55R17 to 255/55R18.  But I heard about things to checkout like load ratings, wheels offsets and wheel calipers when switching to different wheels sizes.  Could any please assist if the proposed wheels will not pose any such problem. I am not keen to add spacers/modify the car if at all. Many tks and appreciate your advice.

Answer
John,

According to Tire Rack, a Plus 1 size fitment results in a 285/50R18 109LI.  However, I noticed that a 255/55R18 has about the same diameter, but it is an Extra Load, which mean you'll have to use 6 more psi in order to carry the same load.  You'll also have to worry about rim width.

I suggest you work through a retailer to be sure that all the i's are dotted and the t's are crossed.  if there is a problem, then they would need to fix them.