Wheel Size and Fuel Mileage

[M Smith]

Here's a stupid question for 'ya. I'm considering the purchase of an '06 Camry. The model I'm considering comes standard with 15" wheels and P205/65R15 tires - brand unknown, but probably low-end Good Year. I can cough up more mullah (naturally) for 16" Enkei alloy wheels with Michelin tires - exact size unknown.

Holding all else constant, which wheel size would you think would return better fuel mileage? Do you suppose the fuel mileage difference - if any - would be imperceptible?

And finally, what would you choose.

Thanks.

 

[bobo]

Your mileage would be a function of the unsprung weight with heavier wheels and tires adversely affecting fuel economy.

For each 1 lb. increase in tire and wheel weight you are adding the equivalent of 8 pounds to the curb weight of the vehicle.

Apart from the difference in weight of the wheel/tire combo, I believe the wider the tire, the lower the fuel economy.

So you might want to check out the weight of the wheel/tire combination and not go with the widest tires if fuel economy is a consideration.

 

[Ramblin Fever]

Granted I'm basing my opinion off from the fact that I drive an SUV - an Isuzu Rodeo, to be exact.

The truck came standard with 16" wheels, which by the way, to buy tires for are a ridiculous amount of $$$.

Aside from that, I can attest to having had 2 of these exact vehicles, one a 97 the other a 91 - all things being equal on both Rodeo's with the exception of one having came with 15x7 alloy wheels, the other with 16x6 steel wheels.

The 15x7 alloy wheel package, with 31x10.5 tires had MUCH less unsprung weight, versus the 16x6 steel wheel package with 245/75 16's.

I'm in your very shoes right now - I'm tired of the heaviness felt from underneith, I'm leaning towards looking for alloy 16" wheels - BUT only because I already have the tires to fit.

Otherwise I'd be getting the 15's all the way.

Forgot to add - the 16" set-up does get MUCH better gas mileage, but there were engine improvements made in that 6yr gap.

 

[Willy_G]

Usually narrow, tall tires with small diameter wheels give the best mileage. Larger wheels weigh more, as do the lower profile tires. The stiffer sidewalls and wider footprint of the low profile tires also add to rolling resistance.

Also, A 225/55/16, for example, would give make the speedo about 1% too slow…and there aren’t too many tire choices.

As long as you go with a wheel/tire combination that was lighter than stock, your mileage change should be negligible

 

[CapriRacer]

I think there is one other factor to consider:

OE tires will deliver better fuel economy than replacement tires of the same size.

So adding up all the facts - the OE tires and wheels are probably best for fuel economy.

 

[smartboost]

quote:

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Here's a stupid question for 'ya. I'm considering the purchase of an '06 Camry. The model I'm considering comes standard with 15" wheels and P205/65R15 tires - brand unknown, but probably low-end Good Year. I can cough up more mullah (naturally) for 16" Enkei alloy wheels with Michelin tires - exact size unknown.

And finally, what would you choose.

---

205/65R15 is a good size for comfort and economy. If the 16" tires are 205/60R16 then that's worth considering, but 225/55R16 is starting to get big and heavy!

 

[rpn453]

Narrower, smoother rolling tires will give you better mileage. On a car that size, I'd prefer a little wider tire; 215's or 225's. But if you're not into hard cornering then the loss in fuel economy (2 or 3%?) might not be worth it.

Another thing to consider is ride comfort. Toyota tends to put tires that are too small for the rims on their cars, killing the ride. The appropriate rim width for that tire is 6".

Larger diameter tires may increase mileage on the highway by essentially making the gearing a little taller and reducing the effects of road imperfections, but it also raises vehicle height and takes a little more energy to accelerate and decelerate. Within the range of sizes you'd be looking at, the effects of changing diameter would be very minor though. So I'd base diameter sizing on how it looks and fits with the car. I'd need to have the car in front of me to make an actual recommendation!

quote:

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Originally posted by bobo:
For each 1 lb. increase in tire and wheel weight you are adding the equivalent of 8 pounds to the curb weight of the vehicle.

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I realize that a reduction in unsprung weight will improve feel of handling and suspension, but where does this number come from and what does it mean? Do you mean that, if you add 20 lbs to your wheels, the suspension will feel softer or the handling will feel more weighted like you have a 160lb passenger?

[ October 14, 2005, 05:25 PM: Message edited by: rpn453 ]

 

[bobo]

Adding 20 lbs to the tires and wheels may not feel like you have added a 160 lb. passenger, but may feel like you have 160 lbs of sheet metal strapped to the vehicle. I don't mean from a handling perspective, but more so from an overall heaviness standpoint.

You may not notice it so much when cruising, but you would when accelerating.

 

[rpn453]

quote:

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Originally posted by XS650:
In that case, the effect on acceleration would be the same as if twice that weight were added to the unsprung weight of the car. That would be like adding a 40 lb passenger, not a 160lb passenger.

Since the weight is being added at the wheel, not the tread of the tire, the real difference is even smaller.

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Yep. The increase in equivalent static weight for a given increase in wheel weight would be 2x for a ring, and 1.5x for a solid disc. So a reasonable estimate for an automotive wheel would be somewhere in-between; maybe 1.8x, depending on profile.

 

[XS650]

quote:

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Originally posted by bobo:
Adding 20 lbs to the tires and wheels may not feel like you have added a 160 lb. passenger, but may feel like you have 160 lbs of sheet metal strapped to the vehicle. I don't mean from a handling perspective, but more so from an overall heaviness standpoint.

You may not notice it so much when cruising, but you would when accelerating.

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The absolute worst effect it could have on acceleration would be if all the added weight were concentrated along the outside diameter of the tire. In that case, the effect on acceleration would be the same as if twice that weight were added to the unsprung weight of the car. That would be like adding a 40 lb passenger, not a 160lb passenger.

Since the weight is being added at the wheel, not the tread of the tire, the real difference is even smaller.

 

[MarkC]

I recently put larger tires on my Cherokee, going from 215-75-15 to 235-75-15. I realize they're both 15 inch tires, and not a great deal bigger, just wider, and exactly 1" taller than the smaller size.
The only difference I note is that the ride feels better and the handling is a bit better. Gas mileage seems unchanged, and according to the cop's radar (if that can be trusted) the speedo is dead on, so it must have read slow in the first place.

 

[Dominic]

I went from P235/55R16s to P245/50R16s and now I run P275/40R17s weighing about 3-4lbs more per wheel/tire than OE. I still get the same fuel economy on average, and my highway economy has remained identical at 32-33.