Losing MPG?

Very small difference...around 1-2 mpg

 

there are many discussions on here about that...try this thread:

http://priuschat.com/forums/gen-iii...ng-getting-17s-but-i-dont-want-lose-mpgs.html

The actual loss depends on many factors including wheel weight, wheel width, type of tire (LRR or not), tire weight, etc. Pay attention to F8L's signature in that thread...he has a lot of data collected on both 15" and 17" rims.

 

Yes, as pointed out above. Another big factor is the tire attached to the rims. It's easy to drop four or five mpg with the typical tires attached to 17s.

Tom

 

True...I have the LRR Michellin tires on my 17's

 

So do I.

 

That's really only true with the factory 17". Wider and less aerodynamic rims will cause further drop.

 

I am inclinded to agree but I'm not confident enough to make such a statement. I'd love borrow a set of OEM 17s to see if they increase my mpg vs. my lightweight (15-16lbs) Centerline RPMs. I find it hard to believe that the possible better aerodynamics of a 24lbs wheel would improve mpg over a 15lb wheel. I'm willing to test the idea though. For the record my wheels are the same width as OEM 17s and I run the same width tire.

 

Remember you have a Gen II and we're talking about the Gen III. You've reported that the Gen II seems to do worse with larger wheels in terms of mpg hit. You can do the test once you get your BP with solar

I do think aerodynamics is a factor, especially at highway speed, but it's less of a factor than weight.

 

I know. I'm hoping to eat crow with regard to the loss on the GenIII. If so the the 17s will go on the GenIII.

 

The loss contribution from weight increases with stop and go, and bumpy roads.

The contribution from rolling resistance is fairly uniform.

The contribution from aerodynamic drag goes up exponentially with speed.

If you look at those three factors, it's easy to see why there isn't one answer of which is worse: weight or aerodynamics. It all depends on the driving conditions.

Tom

 

Prius uses low rolling resistance tires.
Also, if the outside diameter of the new tires is larger than the outside diameter of the originals.
The size of the metal wheel is not important, but wider tires add rolling resistance.

 

well said, and higher pressure will decrease the 'footprint'. o/p may also want to switch to 15" wheels.