[brucepick]

Please confirm or correct me on this -
Weight of wheels + tires has an affects acceleration and affects mpg when accelerating, but has a nearly insignificant effect on steady-speed driving?

For steady-state driving, reducing the combined weight of all wheels by 20 lb. would be the same as removing 20 lb. of unneeded cargo from the car?

But for accelerating/decelerating reducing that weight would have a more significant result?

I ask because yesterday I weighed the 2 different wheel/tire combinations I have on hand. Nice 205/65-15's turned out to be 4.5 to 5 lb heavier (each!) than 195/75-14's, both mounted on oem steelies. The two have nearly identical outer diameters and so are swappable without affecting speedometer/odometer accuracy or effective gear ratios.