Tigger

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That was an interesting watch. So, if the amount touching the road is similar at full inflation, could I conclude the only reduction in gas mileage when doing normal on-road driving would be the added weight of the wider tires (and not added friction as many of us assumed)?
 

Mark S.

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That was an interesting watch. So, if the amount touching the road is similar at full inflation, could I conclude the only reduction in gas mileage when doing normal on-road driving would be the added weight of the wider tires (and not added friction as many of us assumed)?
Also frontal area.
 

Tigger

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Also frontal area.
Sorry, not following you on that part.

edit: unless that means drag/wind resistance (but I’d think that impact should be somewhat minimal with its proximity to the ground/road)
 


Mark S.

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Sorry, not following you on that part.

edit: unless that means drag/wind resistance (but I’d think that impact should be somewhat minimal with its proximity to the ground/road)
It's surprising how much impact it can have. I'm relegated to my phone, so finding the paper is problematic, but I seem to recall '80s-era wind tunnel testing on a Subaru showing a 5% increase in drag after increasing tire width from 155mm to 185mm. I would imagine the effect of the drag increase is amplified on an aerodynamically clean vehicle, but it's not insignificant even on a brick like our cars.
 

Tigger

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It's surprising how much impact it can have. I'm relegated to my phone, so finding the paper is problematic, but I seem to recall '80s-era wind tunnel testing on a Subaru showing a 5% increase in drag after increasing tire width from 155mm to 185mm. I would imagine the effect of the drag increase is amplified on an aerodynamically clean vehicle, but it's not insignificant even on a brick like our cars.
Thank you sir! When in college and my advanced physics class, we did experiments on tires and friction. So from this video and from my calculus/physics, friction is the least of concerns. I’d say weight > drag > friction (with tread being a part of that last variable) is the correct order for tires influence on mpg.

edit: just as an fyi, friction was much more prevalent on bikes and somewhat on motorcycles as compared to cars and other vehicles.
 
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GoatsyBanks

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Also, for such a light compact suv I have found that it hydroplanes and "floats" on snow easily with wider tires. I have 245/65R17 cooper discoverer at3's. They are highly rated for both of those scenarios. I was already on the fence about getting 235/70's just for gaining an extra .5" in diameter. This video and the vehicle weight has sold me
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