I got 275/40/17 Nitto 555r's for my new rims on the back and they came with 225/45/17 Yoko Advan Neova's on the front. The weird thing is that the sidewall on the 555r's is half an inch taller than the Advan's. How is that possible?

 

275=tread width in mm
40=aspect ratio (IE 40% of 275mm)
17=rim size in inches.

So a 275/40 will have a sidewall of 110mm.
And a 225/45 will have a sidewall of 101.25

Clear as mud?

 

Hmm well he got it down flat