18" wheels & gas mileage

[cptnsolo77]

For those who have went from stock 16s to 18s, did you see a drop in gas mileage?

[vibolista]

I went to a 17 inch wheel and a 225/50 tire... and found no difference in mpg. But it's going to come down to how you drive your Vibe and how wide and tall a tire you put on your wheel.If you stay with the same diameter as the OE wheel/tire combination, your mileage will be easy to figure out (but you're going to have a very low profile tire and that's gonna beat you up unless you have very smooth roads to drive on). If you go with a larger diameter, you will have to figure out the difference between diameters from OE as a percentage and then add that to your odometer reading when you fill up.

[cptnsolo77]

Im very easy on the Vibe. I use cruise control whenever I can, and I never stomp on the gas at lights. Dont understand the math involved to keep the same diameter with a larger wheel though...lol

[keithvibe]

It's not the size of the tire as much as it's the weight of the rims and rolling resistance of the tire design.If you go up in rim weight you will see a decrease of mpg. If you stay close to your stock tire/rim weight package you will see about the same mpg.I get better MPG with my summer 18's than I do with my 16's with winter tires.

[vibolista]

Quote, originally posted by keithvibe »It's not the size of the tire as much as it's the weight of the rims and rolling resistance of the tire design.If you go up in rim weight you will see a decrease of mpg. If you stay close to your stock tire/rim weight package you will see about the same mpg.I get better MPG with my summer 18's than I do with my 16's with winter tires.You're right about added wheel weight, but increasing diameter also pushes the car into a higher gear ratio. So both of those things can hurt mpg if the driver doesn't compensate by being very gentle when accelerating. Last Summer I got 40 mpg a couple of tankfulls, and my wheel tire combination is heavier and larger diameter than OE. For cptnsolo... sidewall heigth will determine the diameter of a tire. An 18" wheel is already bigger than a 16" wheel. In order to keep diameters close to the same as a 205/55 16 tire... 24.9 inches... you would have to use a 215/35 18 tire that is only 23.9 inches in diameter or a 225/40 18 that is 25.1 inches or just 0.2 inches larger diameter than the 205/55 16. My 225/50 17s are 25.9 inches in diameter. A whole 1 inch taller and I could feel the difference when launching from a stop. RPMs are down a bit in 5th gear cruise (good for mpg!). If I had known that I could stuff a 225/55 17 under my wheel wells, I would have done it. The taller tire sidewall give the rim more room away from pot hole damage, generally make the ride softer and lower the RPMs even more at cruise. A shorter sidewall will perform more quickly when loaded into a turn, but will not be as supple (in most cases, depends on type of tire, like extreme Summer performance compared to a touring tire, just as an example) as a taller sidewall. Florida has pretty good roads... Maine has a lot of broken roads due to Winter freeze and thaw cycles and the frost heaving that takes place. Most people with really low profile tires (35 aspect ratio and smaller) bend wheels here. You're taking your chances in Maine with anything smaller than a 45 aspect ratio tire. Hope that helps and is not too confusing.

[cptnsolo77]

Thanks for the input. Yes it does make more sense now. I was just toying around the idea with 17 or 18 inch wheels when its time to get new tires....which will be a while though, so im doing my research now. Appreciate it!

[vibolista]

Quote, originally posted by cptnsolo77 »Thanks for the input. Yes it does make more sense now. I was just toying around the idea with 17 or 18 inch wheels when its time to get new tires....which will be a while though, so im doing my research now. Appreciate it!Doing research is good. Took me almost 10 months to figure out what tire to replace my RS-As. It's an expensive choice you want to get right... since most tires last quite a while... and they really affect your car's ride. So a quasi long term relation.

[Kincaid]

The difference in mpg is small - Car and Driver just did a comparison using a Golf and using stock 15" up to 19" tires. Very informative. It's the issue I just got in the mail, so probably it is the May issue.

[vibolista]

I'll look the article up. I should have mentioned that if you do a lot of city stop and go driving, the larger diameter/heavier wheel/tire combination will probably eat more fuel. If your driving involves moderate speeds with few stops, that same wheel/tire could give you better mpg. Luckily, I don't have to do much "city" driving, living in rural Maine, so probably the reason why my mpg figures are not that bad.