03 LS430 with 225/55-17. Not a fan of the Loprofile/wide tire look. About time for new tires and am thinking of dropping down to 215/55-17. I know the profile of these are the same as my old ones but the width will be a little more to my likeing. I'm hoping for slightly better ride and slightly better MPG.

 

It's not a whole heck of difference, so nothing detrimental there.

Heck, s class and the 01-03 LS uses 215/60/16s for the extra cushy ride

 

The profile may be 55 series but it is not the same. 55 represents a percentage of the tire width, so the sidewall height on the 215 will be less than the 225, resulting in a smaller overall diameter of the tire. Your speedo will be a little off and your mileage may change. Plus you may feel a slightly stiffer ride. Since you are not changing the width of the rim, you won't notice much change in the width of the tire, so I'd stick with the 225s.

 

I agree with you on everything you said especially the part about not changing the rim so maybe no difference in width anyway. Thanks for both of the responders thoughts - that's what I'm looking for. FYI - Here's some math on how much overall diameter is lost (for those considering similar swaps):

Stock size: Diameter = 2*(225/25.4)*.55 + 17" = 26.74"
215/55-17: Diameter = 2*(215/25.4)*.55 + 17" = 26.31"

Difference of .43" (or 100*.43/26.74 = 1.6% less tall.

This is absolutely negligible especially seeing that as the tires wear you lose probably an inch of tread which translates to 2" (7.5%) of overall diameter loss over the life of the tires. Your speedo (even assuming it was accurate with brand new tires slowly becomes inaccurate as your tires wear). So by my figuring 1.6% is in the noise.