I don't know the answer. Can someone provide some insight? Thanks.

 

i would say less; you need more power to move your car because you have more friction. probably negligble.

 

they do, but i'm not sure how much of an effect you will actually see - wider tires give you more inertia to move, have more rolling resistance, and will create more drag.

 

True, but you need to factor in the whole car's design. Every car ever made that got over 40MPG has had skinny / light weight tires wheels. Someone must have figured out that if MPG was the main goal of the car light / narrow tires were the way to go. That said putting 185/75/14 ( I know they will not fit) would not turn the RX-8 into a Honda Insight MPG wise but also putting 50's on a Diesel VW Bug would only slightly hurt the MPG. Also going wide would tempt you to drive harder and use more fuel while skinny tires would make you drive slower saving fuel.

 

wider tires = less mpg. How much? Not sure, but I'll let you be the guinea pig (ha ha).

 

"Rolling resistance" is the key phrase here and you will probably experience more of a drop in mpg by switching to a similar width, less expensive brand (Kumho, Yokohama-personal experience), than you will by increasing the width of quality tires (Bridgestone, Michelin, BFGoodrich). Just my $0.02 worth...

Regards, Art

 

Should I put bycycle tires on my RX-8 then? :D

 

Depends on who makes 'em...are they quality rubber?? :D

 

Kind of a broad question to ask, but it can be answered nonetheless.

Like Art said, rolling resistance is a factor, but the complexity of the question increases as you include vectors i.e. changing directions.

I believe in general, anything you increase is going to hinder your gas mileage. If you're after performance, you're going to have to make sacrifices.

 

Haven't really notice much of a mpg difference, I have 245's/40 instead of the stock 225/45. After I wear down these tires thinking about going to 265/35.

 

but that's not much of a difference in the width of your tires.

yes, wider tires with their associated increase in relative mass, and rolling resistance, and all that, will always increase the amount of energy you need to move them along with your car, compared with a thinner / smaller wheel.

 

I wouldn't be too worried unless your stepping up to a 295 or 335 or something crazy wide which you wouldn't do unless you were making so much power you needed a tire wide enough to put the power down. Switching to a 245 or something I doubt would have much of a noticeable effect.