Has anyone used a larger diameter tire - like a 195/60/15 or greater - to improve highway mileage on an xA. I know the spedo will be off a touch, but I'd lke to get better highway mileage when I change the tires. The car is manual. How large without rubbing? Thanks for any experiences. Mark S.

 

wider tire will decrease gas mileage, as the rolling resistance is decreased. oh and FYI, the overall circumference change is less than 2% so at indicated 60mph, you'd be actually going 61.2mph.. not THAT much of an RPM savings.

the xA/B really just needs a taller final drive..

 

Economy cars traditionally run on skinny, rock-hard tires for a reason - minimum rolling resistance and drag from the tires for maximum economy.

If one compares the mileage of 185/60R15, 195/60R15 and 185/65R15 tires, the 185/65R15 will consistantly get the better mileage ALL OTHER THINGS BEING EQUAL. Thing is, the difference will probably be in the 0.01 MPG range - essentially unnoticible.

One quick takeoff from a traffic light, or one passing romp on the highway, or a couple pounds low tire inflation and the difference is gone... Even driving on a wet road can swamp that tiny difference (no pun intended).

Going to a narrower, higher aspect ratio tire improves fuel mileage, going to a wider, lower aspect ratio tire decreases fuel mileage. Thing is, the changes in ride quality and handling are greater than the changes in MPG in most cases.

 

thanks for the replies. Guess I'm stuck with average 35mpg. The change in tires seems to be a big hassle for just about no gain. My daughter has an Echo and there's about 800 rpm difference at 65 mph. (Echo is lower) and the resulting better economy. Like you said, the gearing is the problem.