Does the 16" Tire Get Lower Mileage Than the 15"

The word on the street is yes, the Touring gets about 5% worse mileage. It could be caused by tire brand as much as wheel size. I've owned both, and I'm getting virtually the same mileage on the Touring as I got on my 2005. Of course I learned how to drive a hybrid on the 2005. Overall I think the difference is below the general noise level of variations from car to car.
I got about 45 winter and 50 summer on both cars, although the 2007 seems to keep getting better.

 

Again... Howdy Tenor1 - looks as if you are enjoying your '07 Prius... and PriusChat is a superior resource to get practical, realworld information.

I drove my '04 Prius for just over 2 years, now my '07 Touring for 7 months. I find that the '07 Touring gets about 10% lower MPG than the '04 did but must comment that the '07 being only 7 months old is still likely a little 'stiff.' My '04 continued to gain MPG up to over 15K miles on the clock. I did run my tires at 40/38 psi on the '04, and choose to run the Bridgestone Turanzas on the '07 at 36/34 psi for a little more comfortable ride - that can definitely affect MPG. All things considered, I believe the '07 Touring is getting very close to the same MPG.

CIAO

 

I suspect the 16" Wheels have higher un-sprung weight which would result in lower mileage by some amount.

 

The 16" tire (wheel) should have mileage that is 1" higher than the 15". Well, actually, 0.5" higher since half of the diameter is above the axle. Hope this helps.

Tom

 

It doesnt
The larger wheels have lower profile tyres
However there may be a couple of percent difference in rolling circumference.
How are miles being measured in these mpg tests?
with the car or sat nav?

In theory the increase weight of aluminum wheel should be less than the reduced rubber and air
so the larger wheels should have higher mpg

 

The touring's bridgestones have max sidewall of 51 psi, so for those not wanting to go above the psi limit (are the integrities 42 on the base?) this could make up some of whatever is lost by the bigger rims/wider tire.

 

Yes and no !! b/c I am not sure if you are comparing the touring vs the regular Prius. Now, what kind of answer is this??? My situation is this: I changed my 15" OEM for 16" wheels and tires, so this may not apply to your question. Some 16" wheels with your choice of tires may give you a lower profile.
So, given the dimensions of your Integrity OEM tires and wheels compared to the dimensions of your new 16" setup, the difference can be calculated by the program presented by:
1. www.1010tires.com/TireSizeCalculator.asp?action=submit [or at]
2. http://www.miata.net/cgi-bin/tirescgi
Plug in your data to the formulas, and you will have your answer. Its about 1 to 2% difference, most of the time, either way.

 

Usually, when one uses 16 inch compared with the 15 inch wheel, the increase in wheel weight is
significant. Assuming the wheel width remains the same, the surface area of a 16 inch alloy wheel is
256/225 = 1.137 => 14% heavier. Since you want to maintain the same diameter of the tire (+/1 1/4 inch),
the tire actually weighs less (by a small fraction since only the side wall is reduced).
Assume that the wheel and tire both weigh about 20lbs. The whole package is 40lbs.
14% increase in wheel is about 3lbs. You are looking at 7% increase in the overall tire/wheel package.
A heavier tire/wheel package increase the unsprung weight, but it is more related to handling and comfort than MPG.
However, the rotating mass increase would hurt your MPG but a couple %. More for city driving (F=ma) and less for
highway (just overcoming friction and wind drag).

However, usually when one uses 16 inch wheel, it involves a wider tire (better braking, roadholding g). Then, the
tire weight also increases by 5.4% (say, 195/185=1.054) roughly. The overall package weight would increase by around
10% (7%+5.4% - small sidewall reduction). Therefore, 10% of (40lbs) = 4lbs. 4x4 (4 wheels) = 16lbs.
With such increase in tire width and wheel diameter, your Prius has to maintain the rotating mass by an extra 16lb.
That would eat into your MPG by a couple percents.

What one gets from all the sizing up is
- better roadholding (shorter sidewall and wider contact surface)
- shorter braking distance (emergency)

 

weighing them is the only real answer
the weight of air counts especially at 40psi

However the real issue is rolling resistance
I's have thought the lower profile tires are stiffer and so roll easier
How to measure that?