Downsizing tires for mpg

A

Adria Ardevol

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Los Angeles, CA
Hello all- I am the happy recent owner of a '99 4.0. Previous owner added all terrain 31' tires. I hardly offroad and am looking to downsize to something more stock level, maybe 27', that is more fitting for cruising in the city.

Do you guys have any insights on the mpg impact ? I imagine most folks have gone up from stock to 31 or so. I hope to do a quick calculation to see whether to change now or wait until the tread thins out.
 
Tread pattern has more to do with it then size IMO
Goto a 31”-32” all weather street tire

Imho the original tire was way too small for these

Keep in mind your trip meter isnt accurately counting the miles per tank with the larger wheels unless you modified the speedo gear also

 
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I doubt going from 31s to something smaller will have much impact on mpgs. Going from 35s or larger to smaller than 31s....yeah might be noticeable.
 
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I went up from 225/75R15 to 235/85R16 and fuel consumption went up by 0.5l/100km (was 12.5l/100km, now its 13l/100km). But both sizes are quite small. Maybe try getting smaller tyres. But I don't think there is much to gain. Maybe you need to be more gentle to your throttle.
 
It might be useful to know what Adria is getting for mileage.
 
Good idea. I got 2 extra mpg (and strange looks) when I downsized from 35s to 28s. ;)
Khaki Jeep 1.jpg


tan jeep lifted small tires (2017_11_20 00_38_12 UTC).jpg
 
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If you’ve got a smart phone download one of the Speedo apps and verify your speedometer is accurate. My Jeep sometimes gets 18mpg with 32” tires on. It’s a bit of a unicorn in the gas mileage comparison. Most folks on here don’t come close to that mpg.
 
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TJ Jim said:
If you’ve got a smart phone download one of the Speedo apps and verify your speedometer is accurate. My Jeep sometimes gets 18mpg with 32” tires on. It’s a bit of a unicorn in the gas mileage comparison. Most folks on here don’t come close to that mpg.
Click to expand...

I usually verify mine when Cops have their radar traps. I got out of a reckless driving ticket at 3am with my XJ. I work every night and know where they set up. Cop pulled me and clocked me at 65 mph. I explained to him that I see him in the same place at least 5 days a week and I purposely drive exactly the speed limit of 45. I even took a pic of my speedometer when I saw his lights in the rear view. I told him maybe he should have his radar calibrated before handing out tickets and screwing people with their insurance companies. He told me to have mine calibrated too. I told him I just did it myself and it's accurate (see pic I just took). I also said there's NO WAY my speedometer would be off EXACTLY 20 mph (reckless driving charge). 🥳
 
andyj said:
I went up from 225/75R15 to 235/85R16 and fuel consumption went up by 0.5l/100km (was 12.5l/100km, now its 13l/100km). But both sizes are quite small. Maybe try getting smaller tyres. But I don't think there is much to gain. Maybe you need to be more gentle to your throttle.
Click to expand...

Speak American, dammit! 🤣

It's early but I think that math works out to about 0.6mpg.
 
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weight of tire is another consideration, If you down size you could move from a C rated tire to P rated passenger tire. drop 5-10 lbs per tire is significant move in rotation mass and likely get you a solid 1mpg
 
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