My dilemna: I daily drive my Unlimited Rubicon, and use a set of 31" all season tires. When I go wheeling I swap over to my 35" tires. I want to upgrade to a 37" tire, and will need to swap out gears at that point, however, I don't want to be stuck running 37" tires all the time.

How tall of a tire can I go without having fuel mileage suffer ? Can I run a 33" tall tire and keep it skinny ? I'm having a tough time finding tall skinny non agressive tread tires without going to a 24" wheel or something.

 

I'm not saying it ain't true because you have a case to prove it, but it still doesn't make sense given the RPM range and the power curve.

 

Best I can get is 16ish MPH

 

This past weekend I was amazed... I still have 3.21s and run 35s. I stayed in 6th gear (around 1600 RPMs) and around 65 mph, which was way under powered and I would need to downshift on any even slight incline...but I got 17.4 MPG. Best I have gotten since I put the lift and tires on. I always thought if the rev band was around 2500, that was ideal, but I don't quite think so anymore. I have been a proponent of this idea for a while, running around town in 5th gear doing 65, but now I think I have changed...

Planman - you have the SUperchips or a programmer or anything? Explain how the great mileage with 5.38s???

 

That is extreme, do you have like 400:1 gears to get at best 16MPH? J/K we all knew what you were meant but I had to say it anyway

 

I understand your explanation and agree with it. I just don't think it's necessary to cruise quite as high as 2500 RPM to be on the power band and every few 100 RPM seem to make a difference in fuel economy above ~2200 RPM.

The difference between 5.13s and 5.38s is only ~100-120 RPM so it should not make a lot of difference. In any case, I was not fortunate enough to have 5.38s as an option when I chose my gear ratio otherwise I might have gone that route.

 

I have 34's and 5.13's and get around 17mpg. The motor is not down shifting and seems to run smoother. If I drive it like a race car, it gets 15mpg.


Auto
No tuner
stock air cleaner and exhaust.

 

The rpm at which the motor cruises at makes sense. However, a huge factor is also tire width. Driving around with a 12.5" wide tire is bound to kill mileage especially on the highway. I once read that each additional inch of tire width would kill 15% of your mileage.

So is there a tire that is tall but skinny ? And not an Interco LTB or something with crazy tread.