How important is weight of tire?

[Trauma PA]

I am looking at putting the 63 lb. 37x12.5x17 BFG KO2s on my 3.6 L gasser with 3.73 gears. Likely mated wheel will weigh less than 30 lbs. I am currently running stock Willys wheels and 59 lb. 285x70x17 Nitto Ridge Grapplers and the 3.73 gearing handles this set up well.
So my question is will my current gearing handle the increased diameter and weight of the 37” KO2?

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[JT1]

I am looking at putting the 63 lb. 37x12.5x17 BFG KO2s on my 3.6 L gasser with 3.73 gears. Likely mated wheel will weigh less than 30 lbs. I am currently running stock Willys wheels and 59 lb. 285x70x17 Nitto Ridge Grapplers and the 3.73 gearing handles this set up well.
So my question is will my current gearing handle the increased diameter and weight of the 37” KO2?

Define handle. I have 37s on 3.73s with a manual. There is a very limited window where 5th (overdrive #1) is usable. 6th is a no-go. I have 5.13's sitting here waiting on an install window. Will it break your jeep? No. Will it be terrible? Yes. If you want 37's, plan on a regear. 4.56 is the minimum I would consider if you are paying for it, but 4.88's or 5.13s depending on your use case should be what you land on.

 

[Wheelin98TJ]

You'll want to regear for 37s.

Diameter is a bigger factor than weight.

Post #14 at the link below explains why diameter is a bigger factor than weight.

https://www.jeepgladiatorforum.com/...tire-i-imagine-damage-is-the-same-also.56271/

 

[Trauma PA]

You'll want to regear for 37s.

Diameter is a bigger factor than weight.

Post #14 at the link below explains why diameter is a bigger factor than weight.

https://www.jeepgladiatorforum.com/...tire-i-imagine-damage-is-the-same-also.56271/

Thanks!

 

[LostWoods]

Yeah even with 35s my 4.10 gears feel marginal at best I cannot imagine them with 3.73s though some around here will say it's fine. FL is flat as hell so I guess hills and altitude aren't so much an issue for you but FL drivers are worse than here in PHX and even here I wish I had more gear sometimes so I'm not always in and out of OD.

 

[NachoRuby]

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.

 

[Rahkmalla]

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.

 

[Trauma PA]

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.

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

 

[In3briatedPanda]

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

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.

 

[Wheelin98TJ]

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

3.73 and 35s is ok, but it's definitely not ideal.

I have 35s with 3.73. It rarely sees 7th and 8th. Needs 4.88 gears.

 

[Rahkmalla]

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

you'll lose 8th gear minimum. maybe 7th as well. more tolerable in acceleration, but still not enjoyable

 

[jmdwifi]

I have 35s with 3.73. They are Fuel rims with BFG KO2s. It definitely feels more sluggish. I took an almost 3 mpg hit. I see 8th rarely. I ordered 4.56 gears and am waiting for the shop to have an opening to install.

 

[Fouts]

No.

 

[jmdwifi]

yes

 

[WILDHOBO]

If this was a poll, regearing would win by a landslide. I agree. I’m running 37’s with 5.13’s and can still feel it a bit. But I see all 8 gears on the highway. 37’s are big. I love having them off road, but miss the 33’s on road. No regrets though. It’s amazing on the rocks.

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