I have experienced 14, 15 and 16 rims on my sdl.
Lower profile sends more shock thru to the chassis.
I couldn't feel a change from 14 to 15s but did notice it when 225/55/16s went on....BUT the improvement in control is worth the tradeoff.

Another thing to consider is the model of the tire...sporting and higher speed rated tires usually have stiffer sidewalls and noisier tread patterns.

My brother's LS 430 went from very quiet to silent when he changed from performance tires to 'touring' tires. Not just a drop in noise but overall smoothness as well.

I try to get the lowest speed rated tire the shop will install on my car...not for cost but for softness.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods