terrylin

iTrader: (5)

True or false - the bigger the tire, the worse off your MPG?

SC510

pretty sure it's true, or at least for me. lol. i ride 20's in the city and i get around 13-15 the gallon. it's for the fact that the bigger the rim, the more force that is required to rotate it, in turn more power from the car which equals less mpg. or at least from what i;ve been told, but hey, wut do i know? you could also try using the search button.

masagsxr

True.... Also the wider it is the less mileage you get.

sc-driver

iTrader: (7)

if your overall diameter is bigger then stock, then of course your speedometer will be off by a couple miles per hour. So in reality, you've traveled a bit farther then what you have really gone. So it will also be less.

scENFORCER

What about odometer? I'm guessing that'll also be off too?

What if you have say 19" TE37's, the wheel is large but extremely light. So your covering more ground and using less force. Would this improve mpg? Or is my physics way off lol..

Brendon

iTrader: (1)

Strong yes, with a slight possible no.

In general, if you go for wider tires then that increases your contact patch, which in turn increases friction, which in turn decreases fuel efficiency. At the same time, if you go for lower profile tires, in general your tires will not only be heavier, but the weight will be pushed out further to the edge which will increase rotational inertia, which decreases fuel efficiency.

Of course, you have to also take into account that no two tires are the same. Some low profile tires may actually weigh less than the ones you have currently and therefore might theoretically improve your fuel efficiency (assuming your larger rims are lighter as well). Also, some tires have much lower rolling resistence (i.e. less friction) than others, so you may actually find wider tires that will be more fuel efficient.

Unfortunately overall, the very point of going wider requires that you sacrafice fuel efficiency. Having wider tires with a low rolling resistence defeats the purpose of going wider. The point of wider tires is to have more resistence so that you don't break traction so easily under heavy acceleration.

terrylin

iTrader: (5)

Good information, thanks guys. On a side note, I saw that my front left tire was running low. The gauge measured it at 12 lbs when all the other tires were hovering around 30-35 range. Just filled it up to that range as well, so hopefully my MPG will go up. Anyone know how much air in terms of lbs we should be filling up the tires with? The tire instructions only have it measured in PSI, but my gauge only has metrics of lbs or kgs. Thanks.

QwkSC

iTrader: (1)

32psi at all 4 corners, it's in your glovebox.

TumblerZ30

iTrader: (4)

I'm confused , if whatever gauge you have measures lbs then it should be PSI. Just to be sure you are clear, PSI = lbs per square inch.

sc-driver

iTrader: (7)

Tire pressure plays a HUGE role in mpg. Fill them up to proper pressure and you'll see a difference.

terrylin

iTrader: (5)

ahhh, thanks! i was wondering why everything says psi and not pounds. i thought the "p" in psi stood for pressure, but pounds and lbs makes more sense. thanks! and 32 psi, very good to know...

IOWNALEXUS

iTrader: (14)

i usually run 35-36 psi on all 4 corners, 245's up front and 255's in back. I average 25mpg.

LEX_MAN

iTrader: (2)

Actualy if you driving most highway miles you will save gas with bigger tires. Highway does not require a lot of power ,so the RPM's will be lower and not much force to counteract(spl). Thats why some v8 have the option of shutting down the 4 cylinders while cruising the highway, to save gas.

Makes sence?

terrylin

iTrader: (5)

interesting, lex. what about the highways in southern california? most times analogous city driving...ineedansc3 - my tires are the standard 16 (225/55/16) - do you know how much is too much psi? i dont want it to blow on me.

Brendon

iTrader: (1)

32 psi recommended? lol i always keep my summer tires at 46 psi and my winter tires at 39 psi (5 below the maximum). What everyone says about uneven tire wear is bs. my tires are wearing pretty evenly. besides, its bragging rights to my friends to tell them my 12 year old V8 is more fuel efficient than their brand-new 4 bangers and V6s. Right now I'm averaging 25MPG with approximately 30% city, 70% highway. Not bad considering the pre-vvti SC400s were rated at 18/22 MPG by the old standards.