I am getting a little worse gas milage with my new wheels. Is this cause they are recording less milage or is it something else.

 

yeah...your wheels are probably bigger i'm assuming, and with bigger wheels, they rotate less times to go the same distance as a smaller wheel, thus recording less miles on your odometer

 

heres the link to the tire size calculator...it is preeeety cool and will tell u 4 sure whats up.
http://www.saturnperformance.com/tech/tiresize/

 

Hey there. Keep in mind also, that if you are running wider tires than stock you will get less mieage too because of more road contact. My 2 cents.

-E

 

Dude...sup with the name? Especially living in South SF...man, guess we won't be seeing you at the `Stick on Sundays...

 

Heh... I was waiting to hear something about my screen name. lol I've always been a Raiders fan. :twisted: Hopefully there will be something to cheer about next season.

-E

 

Which would mean that he would be getting better gas mileage, which isn't the case.

 

no i think that it would be the case i check my gas milage by milage recorded divided by gallons put in

 

I was just pointing out the false logic. Keep checking the mileage, anfter 5 more fillups take the average of the 6 and see what it's like.

 

Guys, normally the tires you get with your bigger wheels have a shorter sidewall, so the overall outer circumference of the TIRE is the same. So there shouldn't be any major change in your odometry.

do a search on google for "miata tire calc" it has a little web program that lets you compare tire sizes to see how far off your speedo will be.

The reason for the mileage drop probably has to do with the wheel/tire combo being heavier. Wheel weight has a major effect on acceleration and in turn mileage as well, due to rotational intertia. Wider tires, as mentioned earlier, will also offer more rolling resistance.

you can try running higher tire pressures to offset this somewhat.

 

if you are running 215/40/17 as indicated in your profile, then there is minimal difference and it would not affect gas mileage calculations much....

those are just slightly larger than stock tire/wheel combo....

what pressure are your tires set at? that could affect mileage....

i have the same size tire/wheels as you and i keep my pressure at 34psi.....

it rides well at that pressure and i am getting 27-29mph city driving....

 

Is there any rule of thumb as to what psi to put in to difference size?

 

not quite sure what they are at right now. But I was getting about 29 miles now im getting round 27

 

how many miles are on your xB?

 

just over 14000

 

only a hair difference on gas mileage...

 

yeah but that is noticable when you drive over 100-200 miles a day

 

so put some lighter wheels and thinner tires back on

youll accelerate quicker too.

 

Would getting 18's or 19's make it much worse than stock? :?

 

any heavy wheel could

18s/19s tend to be heavy