Tires and Fuel

[NOMADIC_LJ]

06 LJ
I6 4.0

I'm coming up for new tires in about 3 months. I currently run 285/75/R16 M/T with the stock 4:10 gears. I've been kicking around the idea of dropping down a size to 265/75/R16 M/T. I don't really wheel that hard anymore and with gas going up this has become a factor. My rig has become more of a camping rig that can get into some nice places.

PRO:
- Better gas mileage
- Less stress on the drive line components

CONS:
- Aesthetics: not sure how it would look as I have a 3.5" lift
- 1" true clearance

Price is a wash as there is only about a $10 difference. So I guess my main question is how much of a difference does it make in MPG to drop 1" in tire size?

 

[bob91yj]

I think about going to an AT style tire while you're at it unless you really need MT's for your area.

 

[CA-RJ]

I had an LJ Rubicon just like yours. I started on the stock 245/75R16's and then went to 285/75R16's. I'm a pretty conservative drive so I didn't really see a huge difference in MPG's when going to the larger tire. If you are looking to go smaller, how about getting a set of 265/75R16's? I think they will look a bit small with your lift, but in the end you're the one who has to be pleased. The milder the tread pattern, the better your mileage will be too.

Here you can see that my fuel mileage really didn't change much going from 31's to 33's.

 

[K2ZJ]

Have you adjusted your speedometer or are you correcting for the larger tires? If not your Jeep doesn't think it is going as far as it actually is. You may be getting better mileage than you think.

 

[NOMADIC_LJ]

Have you adjusted your speedometer or are you correcting for the larger tires? If not your Jeep doesn't think it is going as far as it actually is. You may be getting better mileage than you think.

Even with stock tires I don't trust the speedo. I use a GPS to calculate mileage.

 

[NOMADIC_LJ]

I had an LJ Rubicon just like yours. I started on the stock 245/75R16's and then went to 285/75R16's. I'm a pretty conservative drive so I didn't really see a huge difference in MPG's when going to the larger tire. If you are looking to go smaller, how about getting a set of 265/75R16's? I think they will look a bit small with your lift, but in the end you're the one who has to be pleased. The milder the tread pattern, the better your mileage will be too.

Here you can see that my fuel mileage really didn't change much going from 31's to 33's.

Thanks! I can't tell on the chart where you switched tires sizes.

 

[jeffy]

Have you thought about going to 255/85R16's? You'll have a bit of weight loss while also reducing the roll resistance. Going with an AT instead of a MT would also help. I was looking at KM2's and the weight difference between 31x10.5" and 33x10.5" was only a 4lbs increase compared to the 13lbs for 33x12.5". Some brands are also a lot heaver then others. Goodyear MTR Kevlars come to mind.

I think the aerodynamics are what's really killing your mileage. Do you drive much over 65MPH? If you dropped your speed to 55MPH you would probably notice a decent change. Perhaps more significant then changing tires. Although this isn't possible all the time. Some highways are just fast. and driving slow with fast traffic can be dangerous.

Good point about calibrating the speedometer. It's cheap to do and not only gives you an accurate reading but also helps the PCM as it reads the signal from the VSS as well.

I'm in the same boat as you. I'm running 35x12.5R15's and thinking about downgrading as well.

 

[NOMADIC_LJ]

I think about going to an AT style tire while you're at it unless you really need MT's for your area.

I had an A/T before I had the M/T's and I just can't see myself going back. The tires I'm running are more of a cross-over hybrid type, not really a true M/T so I guess that helps a bit on the road. I run in pretty tough terrain when we go to the mountains so that's where the M/T really comes through.

 

[Redline]

x2 on the 265/75R16 instead of 265/70 mentioned. 265/75 will offer lots of tread choices.

x2 on the 255/85 option. This will keep your height (actually increase it), look good with your lift, and help with mpg (like the 265, though maybe not quite as much) if you do your part.

 

[NOMADIC_LJ]

x2 on the 265/75R16 instead of 265/70 mentioned. 265/75 will offer lots of tread choices.

x2 on the 255/85 option. This will keep your height (actually increase it), look good with your lift, and help with mpg (like the 265, though maybe not quite as much) if you do your part.

My bad that should have read 265/75R16 not 70

 

[alosix]

I personally think that tire change is going to be a bit of a wash in the gas mileage category.

I haven't looked up the sizes much, but I would focus on skinnier vs shorter if there are any options in that area.

What would really help the Jeep is loosing an inch or so of height, and loosing the roof rack.

Jason

 

[NOMADIC_LJ]

I personally think that tire change is going to be a bit of a wash in the gas mileage category.

I haven't looked up the sizes much, but I would focus on skinnier vs shorter if there are any options in that area.

What would really help the Jeep is loosing an inch or so of height, and loosing the roof rack.

Jason

Thanks Jason. Roof rack is gone and 1" body lift is gone as well. Interesting point on the skinny vs tall, those 255/85R16 are sounding better as I wouldn't loose clearance. Anyone running them have a picture?

 

[sylgeist]

x3 on the 255/85

I also have 35x12.5 and miss my 255/85's. They are tall, but narrow so your don't lose as much in the mileage dept.

 

[alosix]

Thanks Jason. Roof rack is gone and 1" body lift is gone as well. Interesting point on the skinny vs tall, those 255/85R16 are sounding better as I wouldn't loose clearance. Anyone running them have a picture?

I like that size for a rubi. The ones I've driven on the road I've always thought they were overgeared for the ~31s that come stock with them. I 1/2 think the Jeep guys designed the first rubi's for 33s and then the lawyers nixed that idea.

 

[NOMADIC_LJ]

I like that size for a rubi. The ones I've driven on the road I've always thought they were overgeared for the ~31s that come stock with them. I 1/2 think the Jeep guys designed the first rubi's for 33s and then the lawyers nixed that idea.

Agree. Just about any vehicle that comes with F/R lockers from the factory is going to get a tire size increase from stock.

Running 33's seems perfect for me. I can cruise right at about 2400 at 65mpg. I'm kinda leaning toward the 255/85's. I've always liked the old school look of a skinny tire.