Bigger tires vs. re gearing?

[RangerG]

I put 35” tires on my JTR within a month. Ran with stock 4.10’s for a year. It was ok. I regeard a month ago to 4.88. Because my plan is to go to 37” tires when the 35’s wear out. Man what a difference, got my gas mileage back, better off-road performance. I would highly recommend 4.88 for 35” tires. At 75 on the freeway stays in 8th gear all the time. About 2300 rpm’s. Which make me wonder if 5.13 would be better for 37’s.

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[DocMike]

I'm at 6,100 feet. I went to 35s and less than a month later went to 4.88. The 3.73 were awful.
Put me in camp 2. My Jt is snappy and sees 8th gear like it should.

If by “re-gear,” you mean “make your vehicle even more sluggish to accelerate due to the introduction of additional rotating mass,” then sure…it “kind of re-gears your vehicle.”

As is typical with lift and bigger tires feedback, you’re going to get mixed responses: 1. Folks that’s are running huge tires with 4.10 gears and don’t see an issue with it, and 2. Folks that immediately noticed performance degradation and changed out the gears. The best though is the folks that are somehow surprised by the drop in fuel economy.

My recommendation would be to stay with the 35’s unless you’re prepared to re-gear, but you do you. It’s possible that you could convince yourself that the even bigger tires aren’t an issue.

 

[NewGladdyOWNR]

This gear ratio chart is your friend. Going from 32.7” tires to 35“ tires drops your effective gear ratio to 3.83, which is below 4.10, so you will notice a difference in performance. The new ratio needed to get back the feeling of the original stock ratio (4.10) is 4.39.

https://tiresize.com/gear-ratio-calculator/

 

[Blackjeepjk]

This gear ratio chart is your friend. Going from 32.7” tires to 35“ tires drops your effective gear ratio to 3.83, which is below 4.10, so you will notice a difference in performance. The new ratio needed to get back the feeling of the original stock ratio (4.10) is 4.39.

https://tiresize.com/gear-ratio-calculator/

Agree. Just keep in mind that most 35’s, 37’s, 40’s don’t actually measure what they are labeled. Some manufacturers much worse than others.

 

[DocMike]

Which is why I went to 4.88 and not 4.56 with my 35s. Sweet spot for wheeling and dd use in Colorado is 2.5 lift, Rubicon fenders, and 37s. IMHO. (not starting a flame war here) Some run 3.5 in....matter of preference. Most guys run 5.13 out here with their 37s which is a wise choice. Especially if towing.

It sucks....the idea of spending a few grand on something you don't see on your jeep...it's not a winch or a cool light bar.... but I use my gears every single day.
And it's funny as hell when people think you are drag racing just due to gearing and normal driving.
They don't expect it to go off the line like it does.

This gear ratio chart is your friend. Going from 32.7” tires to 35“ tires drops your effective gear ratio to 3.83, which is below 4.10, so you will notice a difference in performance. The new ratio needed to get back the feeling of the original stock ratio (4.10) is 4.39.

https://tiresize.com/gear-ratio-calculator/

 

[WILDHOBO]

So many variables. 4.88 might have worked “fine” with my 37’s at sea level with no hauling, but I’m at 8,600ft and tow and haul over mountain passes. 5.13’s were the minimum, and work very well. In FL, I wouldn’t even lift it. And would keep the stock tires.

 

[JD101]

Can’t argue with that. I just get frustrated with people tell members they don’t need to regear. Choosing not to when mounting 35’s, knowing a small performance hit will occur, is completely reasonable.

Agree here too. What will work , and what will work rite are two different things . There is always an acceptable middle ground for each circumstance, but even that isn't ideal. It's misleading to push the agenda that no regear is needed because the truck physically moves . Sure it will, but at what cost ? Alot of the moderate to extreme mismatched cases are reports from folks who don't even have experience driving a before and after regear of the same build .

 

[1996XJ]

So... the real question is do you run 35s on the 4.10? Is it over working the jeep to run the 35s on 4.10?

 

[Jteakus]

Interco has a good calculator
https://www.intercotire.com/tire_size_change_gear_ratio_calculator

 

[DocMike]

Drive one after a regear.. you will regear.
Unless it's a JTRD.
Diesel guys can run 37s.

Always happy to let someone drive mine. I was behind a Jk this weekend that needed a regear....my god.....painful.

Agree here too. What will work , and what will work rite are two different things . There is always an acceptable middle ground for each circumstance, but even that isn't ideal. It's misleading to push the agenda that no regear is needed because the truck physically moves . Sure it will, but at what cost ? Alot of the moderate to extreme mismatched cases are reports from folks who don't even have experience driving a before and after regear of the same build .

 

[TexasLEO]

The guys running 3.6L with 37”tires and geared in 4.88 and 5.13, what is y’all’s actual mileage?

I have a stock Rubicon getting about 14-15 city.

 

[GOT FLOYD]

I put 285/75/17 ( about 1" taller over stock ) on my Mojave with 4.10's and my speedo is off 1 mph. Transmission is perfect

 

[JD101]

The guys running 3.6L with 37”tires and geared in 4.88 and 5.13, what is y’all’s actual mileage?

I have a stock Rubicon getting about 14-15 city.

Mine was about 15 ave or 16-17 hwy if I behave myself with 37x12.50r17 and 5.13s @ 70ish I have chopped fenders and a winch pushing wind also .

 

[Barnaby’sdad]

So... the real question is do you run 35s on the 4.10? Is it over working the jeep to run the 35s on 4.10?

As dealers sell 4.10 equipped JT‘s with 35’s (keeping the factory warranty), the answer to that is likely ‘No.’ That being said, you’d have to make the call on whether or not it’s going to be a drive-ability issue for you.

Network. I’m willing to bet that you could find someone local via a Jeep group that would be willing to let you drive their rig so you can test it out before you make the spurge.

 

[Trippin01]

I re-geared to accommodate my usage with 37" tires. I pull a 4k lbs trailer, and I find myself in rock gardens on BOH trails every summer (Rubicon is next). I tried leaving the 4.10 gears on, but in both of the afore mentioned scenarios, performance lacked. Dropping to 5.13 gearing worked perfect for me. Smother control in the rocks, and more low end torque to the road when pulling the trailer. Top speed took a hit, but 65-70 works just fine for me. My JT is nothing more than a trailer pulling, off road toy and thats all it gets used for. I have a 35 mpg car for car stuff and daily transportation.

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