BFG Tire Size and Gearing

[Rockaholic]

I know that the BFGs are known to run small but how does that affect gearing?

When deciding to regear, are the tire measurements based on the nominal or actual dimensions of the tire?

I have K02 37s and they measure just a hair over 35 on the truck at 37psi.

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[Lunentucker]

It's based on actual, and weight matters as well. Tires are another gear. The gear on the treadmill of the road or trail.

 

[Rockaholic]

It's based on actual, and weight matters as well. Tires are another gear. The gear on the treadmill of the road or trail.

I am a new jeep owner and the general consensus seems to be that 35s are OK with 4.10 gears but that once you move to 37s that gearing is almost necessary. My experience so far has been that my driving experience has been OK but not amazing, especially with towing. I see 7th and 8th regularly on the highway but it stays in 4th when I am climbing a hill with my light trailer. I get about 13mpg combined. If I decided to regear would 5.13s be too much?

 

[Lunentucker]

I am a new jeep owner and the general consensus seems to be that 35s are OK with 4.10 gears but that once you move to 37s that gearing is almost necessary. My experience so far has been that my driving experience has been OK but not amazing, especially with towing. I see 7th and 8th regularly on the highway but it stays in 4th when I am climbing a hill with my light trailer. I get about 13mpg combined. If I decided to regear would 5.13s be too much?

I run the K02 35's on my Mojave with 4.10 gears, and the difference from the stock 33's has been negligible. I tow a utility trailer from time to time and it does fine.
Many run 37's on the stock 4.10's as well.
Personally, I wouldn't regear for either.
8-9-10 speed transmissions are going to shift a lot with minor terrain changes. They're designed to do that.

 

[Rockaholic]

I run the K02 35's on my Mojave with 4.10 gears, and the difference from the stock 33's has been negligible. I tow a utility trailer from time to time and it does fine.
Many run 37's on the stock 4.10's as well.
Personally, I wouldn't regear for either.
8-9-10 speed transmissions are going to shift a lot with minor terrain changes. They're designed to do that.

That's good to know, thank you

 

[Yman70]

I have the 37" KM3's with 4.10's and will be regearing to 5.13's shortly. I'm in AZ so this will help when going up north to Utah. Currently the truck sees 8th gear unless I have a slight incline like an overpass. If it's windy it stays in 7th gear.

 

[Bruticus Maximus]

I am on 37" KO2s and regeared to 5.13s. Zero regrets. It drives and runs great! Gained a couple MPGs on the low end, which is where I spend most my driving, going to/from work and on the local trails. See 8th gear now on the highway as well. Truck feels more efficient. I currently am not towing anything but am considering either a trailer or canopy camper.
But I know guys who run 37s with stock gears and have not had any issues. Not sure if any long term issues would arise though. Really probably depends on how you run it and how much you are towing or hauling around.

 

[Rockaholic]

I am on 37" KO2s and regeared to 5.13s. Zero regrets. It drives and runs great! Gained a couple MPGs on the low end, which is where I spend most my driving, going to/from work and on the local trails. See 8th gear now on the highway as well. Truck feels more efficient. I currently am not towing anything but am considering either a trailer or canopy camper.
But I know guys who run 37s with stock gears and have not had any issues. Not sure if any long term issues would arise though. Really probably depends on how you run it and how much you are towing or hauling around.

Do you have any problems with high RPMs at highway speeds?

 

[JeepOfTheseus]

Do you have any problems with high RPMs at highway speeds?

Runs right around 2200 for me, with the same setup. Love the combination.

 

[Bruticus Maximus]

Do you have any problems with high RPMs at highway speeds?

As with ryanlsmith, low/mid 2000s RPM. I never go much above 75 though, as the truck is a brick on wheels and things start shaking.

 

[Rockaholic]

What brand of gears are you guys running? Do you like them?

 

[JeepOfTheseus]

Yukon for me, and yes. Problem free.

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