Do any of you scion gurus have any formula to determine how much better gas milage i will be getting?

I had 18's on the xb and was getting about 25mpg. I just put my stock wheels back on and decided to weight them before i did. The stock wheels weight 35lbs vs the 18" wheel which weigh 43lbs. So a difference of 8lbs a wheel.

Any ideas? or do i just wait and see? I can only hope it gets better since i drive 100 miles a day all highway on my auto.

The other thing i thought of was that my carbon fiber hood seems solid if you try to pull on it but it flexs and moves around quite a bit when driving. Do you think its possible that this is making the aerodynamics worse and killing gas mileage as well?

 

Lighter = better. That's why you see racing wheels which are like .5 lbs a piece lol.

 

You may find this thread interesting: https://www.scionlife.com/forums/viewtopic.php?t=83040


The stock spec is 37 lbs. That is why I'm going to buy a set of lightweight 17" wheels.

For example the Axis Mag-Lite 17x7 is just 14.5 lbs. and ONLY 11.7 POUNDS for the stock 15" size.
http://www.axiswheels.com/wheels/maglite/mag-lite.html
http://www.wheelmax.com/product.asp?ProdId=10141

The recommended tire size is 205/45x17. Compared to stock, this size gives gives:

Diameter Difference: 2.15%
Speedometer Difference: 2.192% too slow
Weight: ~ 22 lbs
Tire example: http://www.tirerack.com/tires/Spec.j...1=yes&place=16


A 215/40x17 gives:

Diameter Difference: 0.13%
Speedometer Difference: 0.125% too slow
Weight: ~ 22 lbs
Tire Example: http://www.tirerack.com/tires/Spec.j...e1=yes&place=2

So, the 2nd wheel/tire combo gives virtually no difference in OVERALL diameter. However, it is still one pound lighter than stock. Now that is what I'm gonna try to do.

edit-
2 other lightweight 17" wheels at tirerack:
http://www.tirerack.com/servlet/Call...&showRear=null
http://www.tirerack.com/servlet/Call...&showRear=null

 

Wheel diameter (assuming overall diameter is kept equal) is THE MOST crucial part of efficiency. The smaller the wheel, the more hp to the wheels and mpg you get. In fact, the resistance to changes in movement (called inertia) changes with the square of the radius. So that's twice the change in diameter, squared.

Wheel weight is also important. . . but keep in mind, most high performance cars use the smallest wheels possible that fit over their brakes.

 

here you go: the be all end all thread about rotational inertia/

https://www.scionlife.com/forums/vie...tional+inertia

 

well, your MPG will be skewed if you have any difference in tire diameter. I have 215/45/17 mounted on my LunchBox mounted on lightweight 17" Motegis, and, if I adjust for the almost 4% difference in tire diamter, I haven't seen a real drop in actuald MPG if I calculate out the difference.

 

Moved to T&B

 

I still get over 30mpg's and I roll nice beutiful heavy deep dish Works. It's all about driving habits. SOOOOO, if you have to play stoplight GP every time you accelerate, your MPG's will not be good. I've seen some seniors in xB's that I had to race to catch up to in my Daytona! I suppose he is on here b!tchin about his mpg's too.

 

Wheel and tire weight can make a big difference. My 17" Motegis weigh only 14.3 pounds each, and I got them because I wanted to keep gas mileage high. It worked; I didn't see a difference at all in fuel mileage over the same trip during the same time of year with my car set up exactly the same. FYI: I'm up to 41 mpg on my manual xA.

 

Well i have gained 5 mpg going back to my stock wheels with no change in the speed i drive. The tire diameter on the stock wheels is actually larger also so i think it has more to do with weight then tire diameter.