zjnoob

Im looking at two different 35" inch tires with the following weight and height, which one would get better gas mileage?

1- 34" diameter, 75 lbs
2- 34.5" diameter, 65 lbs

jkman77

Worried about gas milage stay stock or get a little car.

StrokeHerAce

Yes, in more ways than one actually.

1) weight ---more weight you push less MPG bigger tire more weight
2) hieght ---the taller it is the lower you are making your final drive gear ratio. the lower you make it the harder the engine has to work on uphill or level ground.
3) width ---see #1

Now to answer your question in way you most likely do not want to hear. There is a good reason one tire is 10 pounds heavier. Most likely one has a more aggressive tread or thicker sidewall causing the extra weight. A more agressive tread will also make lower MPG to a degree. Overall what you are looking at is very little change between the two tires. Due to gear ratio the heavier tire will most likely get better milage. Weight has far lees of an effect than actual tire size.

Another alternative is to run different size and type tires as I do. I drive mone on an all season tread for daily driver functions and switch to a mud grip when I am going to go offroad. Rarely do I hit more than 40-50 miles on highways with my offroad tires unless I don't have a storage area for the trailer where I am going.

Tgoods 09 X

Or we could not be a dick and help the guy out. Now that that is out of the way

Im not 100% sure but Im going to guess that the heavier tire will have the biggest effect on the MPG's. Takes more effort to get them rolling so more gas will be used. But those tire specs are pretty similar so I wouldn't expect a huge difference between the two. I say go with whatever tire you like better.

Listen to the guy above me he seems smarter.

jkman77

JEEP WITH LIFT AND 34 ISH TIRES. COME ON THE DIFFERENCE CANT BE MEASURED. I LOVE JEEPS TRUE TO THE BRAND AS A WHOLE. BUT GAS MILAGE, COME ON AND GIVE IT A BREAK. DONT BUY A JEEP FOR A DAILY DRIVE IF YOU WANT GOOD GAS MILAGE. FORK OUT THE EXTRA DOE AND ENEJOY..

jkman77

Trust me i have put around 100 miles aday on wranglers for 5 years now. Stock or not they love fuel. Might be the box shape . But they go where i want and when i want.

StrokeHerAce

I have learned from years of large tires and gas guzzlers...



WRONG...my jeep was a MPG upgrade I came from 6K pounds of truck on 39.5 Boggers as a daily driver. Stock 30-31 X is about 21-22MPG for average driver considering 6 speed (auto is lower usually) Rubi is about 1 MPG less. The change to a 33-34 inch tire will drop you anonther 1-2 MPG on average. So now lets look at what this truly does on the low end. Gas = $2.65 per gallon. 100 miles at 22 MPG
4.5 gallons used and 100 miles at 20 miles per gallon is 5 gallons used. So for every 200 miles you save $2.56 big ones. So at 20K miles you have now saved $2.56 dollars which is a new tire. At 200,000 miles you have saved $2560.00 dollars and you can use it to mod your next jeep because you are starting to wear out your current one.

Ghost63

Seems that the original question was not about the overall fuel economy of Jeeps, but what the difference would be in MPG between two different tires.

The heavier tires will result in lower mileage, just as adding extra cargo cuts down on MPG, it is a factor of weight and extra rolling resistance. You will also accelerate brake pad wear with heavgier tires. Ball joints and sterring components also wear fster due to the increased inertia when turn turning and cornering.

zjnoob

Im still trying to wrap my head around this. It seems like the heavier tire would be less effecient when accelerating and overall crusing, it would take more energy to start it moving and keep it moving.

I see your point though, a taller tire seems like it would be less effecient once its moving because it has farther to go, less rpms for the tire, more rpm for the engine. 10 pounds seems like allot of weight vs half an inch so my thinking is the heavier tire would be less effecient.

tpm152

No matter what equipment your JK has, any effects on MPG will be more dependent on your transmission and driving style.

If you have an automatic you will not see any difference in MPG between those two tires. Both in town and on the highway an automatic will downshift more often to get you up to speed or maintain speed up a hill with both a taller tire and a heavier tire (resulting in approximately the same MPG).

With a 6-speed you might see -slightly- better fuel economy with the taller tire compared to the heavier tire (if your driving style on the highway is like mine and you just leave it in 6th most of the time and if you slow down a little on the hills it doesn't bother you). Reason is that you go a further distance due to the larger tire circumference per rotation of the engine assuming gear selection is the same, you will get higher MPG.

However if you are commuting and periodically encounter traffic on the highways (and aren't just cruising along at steady speed for long periods of time) even with the 6-speed I couldn't see the difference between those two tires adding up to much in the way of MPG at all.

Something that I would be considering more than the MPG difference (which will likely be negligible) between the two tires would be the "load range" on the tire. Since the smaller tire is heavier, I am guessing that it could be a higher load range rating. The consideration you should be aware of is that many people on this forum have said how much harsher the ride is when they run a tire with a higher load range compared to a lower load range. The trade-off however is that a higher load range will have more plies and will thus be a tougher sidewall at the cost of a harsher ride.

Just food for thought. If you want a nice on-road ride and only do mild off-roading you may want the lower load rating. If you plan on doing some hardcore wheeling you may want to get the higher load rating so you are less likely to cut your sidewall on the rocks