I’m calling BULL

[PyrPatriot]

Probably scarce in those sizes but when I was shopping I found that if I clicked options, I could choose other than the default C or E for many sizes I was looking at. I wanted to stay 33 or below, though, because I have no reason to go bigger. Bigger is worse on our snow and roads. Wide tires are not the way to go for snow. Tall tires - I don't need to prove anything - and don't need 34s or bigger - Why would I?
They want to SELL you the heavier load ranges so most places won't offer them up, and the default online is always the higher load ranges even if the same tires are offered in lesser ranges.

Unfortunately for me I needed the larger and heavier tires. 33" tires just were not cutting it on the trails (too much belly/diff scraping for my liking) on a few spots I went on a few times a year. Creeks have sharp rocks and a few folks with KO2s reported sliced tires. The larger tires made things more...enjoyable

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[ShadowsPapa]

Unfortunately for me I needed the larger and heavier tires. 33" tires just were not cutting it on the trails (too much belly/diff scraping for my liking) on a few spots I went on a few times a year. Creeks have sharp rocks and a few folks with KO2s reported sliced tires. The larger tires made things more...enjoyable

We don't have trails.
We don't have rocks to crawl over.
We have fields, mud, gravel roads, dirt roads in some parks, etc. even in most of our state parks, all roads are paved.
Hell, every-other road in most counties is a paved farm to market road.
If you go off road here you are in a ditch or a median and the biggest threat to the underside is the concrete culverts. You should have seen the underside of some of the IHP cars I got to work on. Ripped to shreds when they went after bad guys by cutting through medians and ditches and hitting those culverts.
I suppose I could ask cousin Ralph if I could go mudding in his cow pasture after the cattle have gone in for feed. Maybe I could chase them to the trailer for him come market time.

 

[ShadowsPapa]

Life is all about them tradeoffs

Started at 22-24mpgs
Adding 250lbs of gear/accessories: 21mpg
35" tires: 20mpgs
Steel Bumper and Winch: 16-17mpgs

Gear/accessories includes the 100lbs rock rails, a 90lb horse mat for the bed, and various tools/recovery gear

I might get back some mpgs when I replace my Falken MTs, those things are about 100lbs each with the wheels

Steel bumper and winch is where I saw one of my biggest MPG drops. My wife has noticed the drop and I think made the connection - I may eventually opt to put in wiring front and back and move the winch to a receiver mount - maybe, someday. That would take about 80 pounds off the front.

 

[Orange01z28]

If you have a Rubicon / Mojave, the 4.10 gears will help it.

The Sport will be a dog and bad on gas. You also have to recalibrate the trans shift points on the auto or it will constantly shift in and out of gears. If you have a manual, it feels even slower.

False

Recalibrating the shift points and speedometer makes it fine

 

[j.o.y.ride]

False

Recalibrating the shift points and speedometer makes it fine

You dont get any change in MPG from recalibrating the speedometer, all you get is a proper calculation, but no real world change.

 

[Cripton805]

False

Recalibrating the shift points and speedometer makes it fine

So what you're saying is... No MPG difference or? It will take a hit in MPG.
15-25%+ is quite a bit in my opinion, but that's why it's an opinion.

This is from personal experience w/ 35s and lift.

 

[Hootbro]

You dont get any change in MPG from recalibrating the speedometer, all you get is a proper calculation, but no real world change.

A transmission shifting when it thinks it is going 65 mph but actually is 70 mph will have real world change on it's MPG's when it is corrected to actuals.

 

[Mac]

I did not notice any difference in performance when I recalibrated my speedometer for my larger tires, only thing it did was increase my mpg about 1mile on the screen

 

[yolo]

I screwed up with my first round of changes… bought great stuff, but it was too heavy and totally effected gas mileage, ride, everything.

Bit the bullet and swapped it all for aluminum, removed parts that weren’t doing anything, and went to lighter wheels and tires.

It’s a weight game, but you can be creative to get what you want. My 37s and 17s are 20lbs lighter than my previous 35s and you can feel the difference.

What wheels and tires did you go with? Do you know the weights?

 

[kevman65]

Speed you drive at is the most important factor.

I am running 35's on a Rubi with automatic, no lift.

Highway/interstate at 65 MPH on cruise I am averaging 22.5 MPG. At 60 MPH I get 24 MPG. At 55 MPH I get 27 MPG. Now the killer, at 70 MPH I get 18.5 MPG.

Work is 100 miles round trip every day. Interstate and U.S. highway. In the morning I have the road almost all to myself so I can run whatever speed I want and I have tried all the above speeds for a few weeks each.

Did I give up MPG by going bigger, yup, it's a given. Do you have to give up a bunch of MPG's? Nope, it's all on you.

Calibrate for bigger tires, ease up on the skinny pedal, use the cruise control, and you'll still get good MPG's.

 

[ShadowsPapa]

If you have a Rubicon / Mojave, the 4.10 gears will help it.

The Sport will be a dog and bad on gas. You also have to recalibrate the trans shift points on the auto or it will constantly shift in and out of gears. If you have a manual, it feels even slower.

You must mean the base sport with 3.73 gearing as there are sports out there with 4.10 if they have the max tow option. They are still Sport versions......... just different options.

And yet there are Overland owners (which also has 3.73:1 gearing) who have upped tire sizes and have no real complaints. Yes, they lose mpg, yes, it's not as nice as far as using 8th gear, but the automatic won't act much different off the highway. It won't be a dog because the transmission compensates.
There's no reason 33, 34 or even 35" tires would make a basic Sport or an Overland with 3.73 gears a dog - especially taking off from a stop - that's what torque converters and low gears in the transmission do your you. With a stick, yes but an automatic, no - you just use the lower gears more.

 

[j.o.y.ride]

A transmission shifting when it thinks it is going 65 mph but actually is 70 mph will have real world change on it's MPG's when it is corrected to actuals.

Shift point should be driven by engine speed not vehicle speed

 

[ShadowsPapa]

Shift point should be driven by engine speed not vehicle speed

Nope, engine speed and load/throttle position balanced by road speed. It's always been that way.
Shift point on earlier MOPAR systems was controlled by the throttle pressure valve (TPV) which was connected by linkage to the throttle.
There's a governor in those TF 727s, 904s, 998s and so on. That sets the governor pressure.
Once that pressure overcomes the throttle pressure, the next shift is initiated.
If you push harder on the throttle, you increase the throttle pressure and delay shifts because the governor pressure has to get higher to overcome it.
These are based on the same ideas, just with different methods of control - and other factors that come into play. Engine temperature, load and other factors.
The pressure controlled by road speed has to overcome the pressure determined by throttle position which is a general indicator of load.
That's over-simplified in today's world, but that's how the basics work.
Throttle position is an indicator of load - more throttle generally means more load, delayed shifts.

I'm sure they are also controlled by engine speed as well as throttle position but vehicle speed absolutely plays into shift points.

 

[Hootbro]

Shift point should be driven by engine speed not vehicle speed

Most modern electronic control transmissions have a input (engine) and output (driveshaft) speed sensors that correlate the shift point data. Basic software programming will also factory in final gear drive ratio. Adding larger tires without telling the software messes up the final gear drive ratio and the data that is provided back to the transmission.

 

[Renegade]

Can I call “bull” on this thread? The sole result will be an argument. Hey, I’ve not tried something, and I want you to prove me wrong. Let’s go!
Physics is physics, so yeah, you’re right. Leave yours alone.

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