I recently put RX8 wheels on my Mazda3 2.0 Automatic, and noticed that my overall mileage per tank went from 315 to about 265. Sound about right? I knew there would be a drop in gas mileage but not that much. Thank god gas prices went down!

 

Quote:

ORIGINAL: vlstellato

I recently put RX8 wheels on my Mazda3 2.0 Automatic, and noticed that my overall mileage per tank went from 315 to about 265. Sound about right? I knew there would be a drop in gas mileage but not that much. Thank god gas prices went down!

What size of tires are you now running? I am thinking that if the tires are significantly larger in diameter compared to the OEM rubber, part of your problem is that you are actually traveling significantly more than a mile for every mile logged by your odometer. That of course also means that when you think you are traveling 70 in a 65 zone, you might actually be doing something over 75, and that in turn might be the difference between a ticket and sliding on through unnoticed.

 

Those RX-8 wheels are fairly heavy, and the weight of the wheel is placed further from the center of rotation (18" wheel)...You increased reciprocating mass. You saw ~16% loss in mileage....that seems a little high maybe, but not out of line.

 

Assumption #1: The Mazda3 came with tires that had an overall diameter of 25.1" and required 832 revolutions per mile.

Assumption #2: TheRX-8 came with tires that had an overall diameter of 25.9" and required 804 revolutions per mile.

Assuming the above is correct, you've introduced a 3.4% error to your odometer (and speedometer), which isn't enough to account for the huge disparity in your fuel economy numbers. So, with that in mind, your economy numbers are probably suffering from a combination ofodometer error and the factors that sstlaure discussed in his post.

 

I couldn"t have said it better myself. However vistellatto, I think you meant to say that the new wheels are Affecting your mileage.
I will fix it for you....

 

Shipo,
P225-40-zr18. Thanks for info

 

Thanks, Virgin1

 

I know I need to get the speedo calibrated but I don't want to buy a programmer now with the Christmas around the corner, it will have to wait. Besides that I had an agliment done because of bad road noise and found that my rear Camber and Toe where off, left side rear camber was 0.41 and the factory spec is 0.09 so now with the car tracking straight I'll see what mileage I get.

Thanks,
Vince

 

Hmmm, that is interesting. The tires that you are running have almost exactly the same diameter and revs per mile as the 205/50 R17s on my Mazda3 i. Assumint that your car came with tires of about the same size, then you can completely ignore my earlier post about speedometer error. Why? Because you have none. []

 

It"s so nice to have some REAL trained engineers on here like SST and shipo, to help put these things into words, isn"t it? Sincerely, Thanks for ALL your help, guys.