Larger tires for better gas mileage?

[Dangfool]

Hello everyone! I've been reading a while, but I'm new posting here.

My question concerns tires. I've long had a theory that I get better gas mileage on my little camper van by switching to larger (diameter) tires, on the theory that this would have the same effect as a higher gear ratio. You know, a few inches further travel for each turn of the axles. As far as I can tell, it does seem to be helping. Has anyone else tried this? What was the outcome? Any thoughts on this?

 

[SternWake]

On a purely highway driven vehicle I believe it is possible.

Larger tires around town though require more torque ( and fuel) to turn them. Also bigger tires weigh more, requiring more fuel to turn them.

I have slightly larger tires from stock and have suffered a hit to MPG. Part of that is the Odometer reading being different, mostly it is taller heavier tires requiring more power to turn.
Also most of my driving is not highway these days.

I recently got a smartphone, and used the GPS feature. My Speedo is right on the money with my slightly oversize tires, which are about 4% larger circumference over stock, IIRC.

 

[Lucky mike]

Narrowing the width of the tire will increase mph less surface area....also look up Hyper mile ing it will teach you alot

 

[Zil]

Two maintenance items still present the best fuel millage. Properly inflated tires and wheel alignment. I keep my tires inflated a little hard and check pressure each week. I get the alignment checked yearly. The cost is well worth the inspection of steering linkage.

 

[crazybill]

Larger tires also throw the odometer off. Hard to tell if you're getting better mileage or not.
-Bill-

 

[user 423]

My question concerns tires. I've long had a theory that I get better gas mileage on my little camper van by switching to larger (diameter) tires, on the theory that this would have the same effect as a higher gear ratio.

If your van has overdrive it's possible you wind up with too high a final gear. It would be OK on flat terrain but it would tend to lug the engine when going up grades. Or it would cause your tranny to 'hunt' too much between gears and kickdown too often which adds wear and tear. This would work best if you drove slowly (60-ish) and left it in 3rd. gear.

BTW: you can get the actual diameter of each size of tire from Tirerack and then you would be able to figure how much your odometer and MPG is affected.

---

PS: Driving slower in 3rd. gear will also give better MPG because there is less drag from wind resistance. Not always an option though.

 

[vanguy]

ya it will probably get better mileage at 60mph, but will stress it more to get up to 60. it will sacrifice some low-end torque.

 

[Dangfool]

Thanks for the replies everyone. Yeah, I'd thought about the loss of torque, and wondered if that would be enough to affect mileage. But I'll keep scratching my head and we'll see what other ideas I come up with...

 

[highdesertranger]

dangfool, I like that screen name. you are correct as far as taller tires give you a higher gear ratio. however will only if(big if) you need a higher gear ratio. as slow day pointed out with overdrive you could now have to high of a gear ratio and will actually get worse mpg. also as stern pointed out your speedo is now off this must be factored in to the mpg numbers. what are you driving? highdesertranger

 

[Dangfool]

Highdesertranger, I'm driving a 2000 Mazda MPV, it's my micro-motorhome. And yes, it does claim to have overdrive, which is always engaged by default. If I turn it off, the van feels sort of like a tractor (but it doesn't feel particularly "overdriven" when it's engaged). Funny, that... Anyway, I replaced the 15" tires that were on it with 17" tires (both sets came with the van, and both are OEM rims, so I don't know which was original), and my speedometer now reads about 2 MPH high. I can have it re-calibrated if that becomes a problem.

 

[Zil]

The odometer is what you want to check. Some highways have measured mile sections, but all have mile-marker posts. If you use the posts as reference, you need to go a few miles to increase the accuracy.