Downsizing tires for mpg

[Adria Ardevol]

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.

 

[CreepinDeth]

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

 

[Link]

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.

 

[andyj]

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.

 

[bucky]

The only downsizing that will get you better milage is to get a Samurai.

 

[jjvw]

It might be useful to know what Adria is getting for mileage.

 

[TheBoogieman]

Good idea. I got 2 extra mpg (and strange looks) when I downsized from 35s to 28s.

 

[TheBoogieman]

The only downsizing that will get you better milage is to get a Samurai.

Their gas mileage sucks too. I had ONE.

 

[Steel City 06]

Good idea. I got 2 extra mpg (and strange looks) when I downsized from 35s to 28s.
View attachment 459608

View attachment 459609

35s to 21s:

 

[R49]

I guess it depends on what one considers poor gas mileage.
My TJ gets 15.5 mpg day in day out.

Not very good for a vehicle of that size and weight, it may have more to do with aerodynamics than tire size.

 

[L J]

Do you guys have any insights on the mpg impact ?

impact: negligible

 

[TheBoogieman]

35s to 21s:

View attachment 459613

View attachment 459614

View attachment 459615

A 5' garage door opening to park in, or you liked the attention of strangers saying how small you look?

 

[Obi-Wan]

35s to 21s:

Somebody skipped leg day

 

[TJ Jim]

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.

 

[TheBoogieman]

View attachment 459623
Somebody skipped leg day

But his arms are enormous.

 

[TheBoogieman]

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.

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).

 

[freedom_in_4low]

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.

Speak American, dammit!

It's early but I think that math works out to about 0.6mpg.

 

[JustDandee]

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

 

[TheBoogieman]

Another dumb shit tire weight thread. The difference is next to nothing.

 

[Apparition]

Another dumb shit tire weight thread. The difference is next to nothing.