How will switching from the steelies to 15" alloys affect mileage? The wheels I'm looking at weigh less than half as much as stock.

 

It should affect MPG just as much as any other weight reduction.

You probably won't notice any difference.

-THE DON

 

this gets into other things: if the new tires are wider, lower profile I'd expect a slightly lowered mpg.

why? I can only guess.. who knows the facts?

 

Also depends on the tire and its rolling resistance.

 

The wider the tire increases the total square inches of rubber contacting the road surface. This increases rolling resistance thus requiring more power to move the vehicle. Extra power over time (distance) equates to lower miles per gallon.

The advantage of wider tires is (or should be), increased traction and better handling in poor conditions (rain) and cornering. But that is also dependent on your suspension and how well you drive. You can have the equipment and still not have the skill or intelligence to hold a corner.

 

Circumference also plays a part. If the circumference of the new tires is greater than the stock tires, you will cover more distance with each revolution of the wheel, and your speedo will read a bit lower than your actual speed. The opposite happens if your new tires are smaller in circumference.

So, in theory, it's possible to break even between losses due to greater friction and gains due to a larger circumference

 

Okay, let me ask youse guys this question. I just put 16" on mine, but the over all profile is the same as the 15". Now, it is a wider tire, that is, the 16"s then the 15"s were.

So, if I understand this, the alloy wheels I replaced, (15"), with new 16" Alloy wheels, although wider, same height, so I will not notice a difference in MPG, right?

Or am I not right?

 

dunno and I'll stand for correction: I think the wider tire must present greater rolling resistance especially because it's wider; that is, when turning, the tire scrubs more against pavement in proportion to its width. Bicycle tires are at one oppostite extreme of this example.

Also, lower sidewalls are stiffer sidewalls (in a way) and so the tire is less springy, less -returning- of deflection energy (bumps, twists) than is a normal aspect tire.

(so I presume but may be wrongggg)