20" aren't that bad. I have 20s in my venza.It might due to change in weight of the wheel and tire.
Driving in Sport mode will also do that.
Honestly my 16 Touring has 18 and virtually no sidewall. I can't imagine you have a sidewall any thicker than a rubber band.
So let's see photos!
This one is the real deal rubberband tire. 315/20R30