New wheels and Tires, reduced gas mileage.

[MetMan]

I purchased new wheels (VMR V710s) as well tires (General Excalim 235/35/19 and 265/30/19) for my Z4 3.0i a couple of weeks ago. Pictures can be found in this thread: http://www.zpost.com/forums/showthread.php?t=360971 .

Anyway, I took a trip from Jacksonville to Orlando to catch the Tavistock Cup and achieved 28.2 mpg for the 297 mile trip cruising at 75mph. This is a decline of about 3 mpg from previous trips with my old 107 style wheels and tires (225/40/18 and 255/35/18). I've also noticed that acceleration is a bit slower than with the 18 inch setup.

If I were to switch the 19 inch tires to 225/35/19 and 255/30/19, should I be able to achieve an increase in gas mileage back to where I was before the switch? The tires have 470 miles on them; what are the chances that discount tire will give me some sort of credit for the 235/265 and allow me to purchase a 225/255 setup for my 19 inch wheels?

[GP20]

The problem is more of the wheels than the tires. The exclaims are fairly lightweight tires and u won't notice much difference going from 235/265 to 225/255. The 19" V710's are pretty heavy wheels and weigh more than the manufacturer's estimate. If you wanna get better gas mileage and acceleration, change the wheels to some lightweight 19~20lbs forged wheels. Or downsize to 18" altogether.

[03BeastCharmer]

+1
Your big heavy wheels are the issue. The weight is further from the center than your stock wheels, so more energy has to be used to move them.

[Hawkeye]

Those wheels look really nice. Worth the 3 mpg IMO!

[MetMan]

Hawkeye, Thanks for the compliment. The car does feel a bit slower in addition to the poorer gas mileage although I have no credible evidence to prove it.

Would going to back to 225/255 width on 19in wheels make much difference?

[The HACK]

Originally Posted by MetMan

Hawkeye, Thanks for the compliment. The car does feel a bit slower in addition to the poorer gas mileage although I have no credible evidence to prove it.

Would going to back to 225/255 width on 19in wheels make much difference?

Not unless you're willing to go to a lightweight forged wheels like someone had already mentioned earlier in the thread.

Even if you were able to find 19" wheels that weighs the same as your original 18" wheels, you will still likely see .5-1.5 mpg decrease in gas mileage because the mass of the wheel/tires are pushed out away from the center therefore require more force to overcome inertia.

On a site like TireRack.com it also shows you the weight difference between each tire sizes.

http://www.tirerack.com/tires/tires....el=Exclaim+UHP

You would gain a couple of lbs up front and lose a few lbs in the rear. Negligible difference.

[3002 tii]

i had vmr 710s in 18s and that was the first thing i noticed. car felt sluggish off the line but they do look great on the car =)

[MetMan]

Originally Posted by The HACK

Not unless you're willing to go to a lightweight forged wheels like someone had already mentioned earlier in the thread.

Even if you were able to find 19" wheels that weighs the same as your original 18" wheels, you will still likely see .5-1.5 mpg decrease in gas mileage because the mass of the wheel/tires are pushed out away from the center therefore require more force to overcome inertia.

On a site like TireRack.com it also shows you the weight difference between each tire sizes.

http://www.tirerack.com/tires/tires....el=Exclaim+UHP

You would gain a couple of lbs up front and lose a few lbs in the rear. Negligible difference.

I have a better understanding now, Thanks!!!

[MetMan]

Originally Posted by Dubbedown

i had vmr 710s in 18s and that was the first thing i noticed. car felt sluggish off the line but they do look great on the car =)

Dubbedown, why did you get rid of your V710s? What was your experience with them?