How important is weight of tire?

[AustinL911]

I ran 35s with 3.73 gearing. took a six hour road trip to roanoke,VA from the GA/SC border, 420ish mile trip and i made it on ONE tank of gas running 70-75 on interstate.

never had an issue with mine.

That's impressive. I get about 320-330 miles out of a tank with my mixed driving. JTR 6sp.

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[In3briatedPanda]

That's impressive. I get about 320-330 miles out of a tank with my mixed driving. JTR 6sp.

I was on fumes.....but we made it. It was probably closer to 400 miles, coming down the mountain is probably how i got there. Google maps says im 359 miles to roanoke, VA so I stand corrected on mileage. It should be closer to 400ish miles.

 

[JD101]

That's impressive. I get about 320-330 miles out of a tank with my mixed driving. JTR 6sp.

I've never seen fuel mileage like that stock driving conservatively . was it a diesel?

 

[AustinL911]

I've never seen fuel mileage like that stock driving conservatively . was it a diesel?

Mines a gasser

 

[JD101]

Mines a gasser

Sorry I was referring to the post you quoted where someone was getting 400 /tank on 35s 3.37s . My mileage is like yours .

 

[Geoarch]

On very light 35s, granted mine is manual, but that's as large as I'd want to go, even with 4.1 gearing. If you're on the 3.73s, you'll hate 37s. Re-gear.

That brings axle stress to mind. I plan on 35s (Kanati 315/70-17s) that weigh 65.4 lbs with a 29 lb Ion wheel, so I don't believe that the stress on the axles will be too much greater than the stock 33s, other than increased radius (my JTR is built and sitting on the Toledo lot). What I can't seem to find is some reports of axle failure with 37s on Gladiators. I realize that 37s are the thing, but I wheel my Tacoma in pretty rough stuff with 31s (and a winch that I've had to use) and it works well. I"m looking forward to wheeling the Gladiator with 35s and the Mopar 2" lift, and ultimately going to 4.88s from the stock 4.10s. Still I'd like to see what effect 37s have on axle life.

 

[Geoarch]

Never forget torque is a measure of force over distance. If you wanted to put 50lbft of force on a bolt with a six inch wrench you'd need to apply 100lbs of force. Meanwhile with a 2 ft wrench you'd only need 25lbs of force.

While it's not 100% accurate, for tires its closer to true than not to assume 100% of the weight of a tire is at the tread for force calculations. Your factory 32s have a 16 inch radius, while your imagined 37s have a have a 18.25 inch radius. Thats a 14% increase in distance, and thus it requires 14% more force to turn that tire.

Now real world, there's more loss than just 14% increase in workload. I dont 100% understand why, but part of it is the starting fact that 3.73 isn't really adequate for 32s to begin with with the gearing either transmission has. 6th (standard) and 8th (auto) are crazy low. And the 3.6 isn't exactly a power monster to begin with. But there's a reason most people recommend 4.88s or 5.13s for 37s when a 4.56 by math alone should be more than enough, and yet everyone says it's not.

3.73s riding 37s at your own peril. You can do it, group concensus is you'll hate it.

The math suggests that with 35s at least, 4.56s should be plenty (4.31 would get to stock final ratio). In another of my posts on this thread I questioned the axle life with 37s, but there doesn't seem to be any data, at least on the Gladiator site. I'm deciding whether to go for 4.56s or 4.88s with 35s. Changing from 33s to 35s, calculates out that the 4.10 ratio is reduced to 3.9, so 4.56s should be more than adequate for 35s including rock crawling and still maintain some semblance of gas mileage.

For 37s from stock 33s with 4.10s the final ratio is reduced to 3.84, and gets back to stock final ratio with 4.38, so 4.56 would be close to stock. Just sayin...

 

[Geoarch]

I ran 35s with 3.73 gearing. took a six hour road trip to roanoke,VA from the GA/SC border, 420ish mile trip and i made it on ONE tank of gas running 70-75 on interstate.

never had an issue with mine.

Go

Great analysis and explanation.
So how about 35s? Can I pull it off with the 3.73 gearing?

Here's the calculation:

Going from 33s to 35s with 3.73 gears, the final ratio is reduced to 3.55 and you'd need to regear to 3.92 to get back to stock. In the current market that would be the Spicer 4.10s, or 4.56s if you wanted to get more power at the expense of gas mileage.

 

[FLUndertaker]

4.10 with 37’s suck. 3.73 would be worse. Don’t let anyone tell you different. If they do they’re either in denial or worse. I suffered with this set up for a couple months while waiting for parts. I went to 5.13 with 37’s and love it.

 

[In3briatedPanda]

Go

Here's the calculation:

Going from 33s to 35s with 3.73 gears, the final ratio is reduced to 3.55 and you'd need to regear to 3.92 to get back to stock. In the current market that would be the Spicer 4.10s, or 4.56s if you wanted to get more power at the expense of gas mileage.

"Go" ?

 

[In3briatedPanda]

Sorry I was referring to the post you quoted where someone was getting 400 /tank on 35s 3.37s . My mileage is like yours .

if you were quoting mine, that was the most i ever got out of a tank of gas, not a diesel. 3.73 gears on 35's I was averaging 17-18 mpg in the city. i drive to and from work mostly, 16 mile round trip.

4.10 gearing im getting 15-16mpg same wheel and tire setup, different Gladiator. Have not taken it to roanoke yet.

Agree that 35s on 4.10 make the jeep peppier from acceleration, but i dont notice any other difference.

I have ZERO experience with 37s and i trust the forum to suggest regearing.

35s, with my pavement princess..........4.10 and 3.73 both fit my needs.

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