Tire Size, Gear Ratio, Affect on Payload/Towing

[ShadowsPapa]

No one can predict how well the change will handle a TOWED load. That's more power than anything, and the roads and speeds you drive. No one can say with xx tires you lose yy% towing capacity. That's based on waay too many other factors besides gear ratio and tire size. It's engine capacity and ability, springs, axles, bearings, heat dissipation, and much more.

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[PyrPatriot]

No one can predict how well the change will handle a TOWED load. That's more power than anything, and the roads and speeds you drive. No one can say with xx tires you lose yy% towing capacity. That's based on waay too many other factors besides gear ratio and tire size. It's engine capacity and ability, springs, axles, bearings, heat dissipation, and much more.

I guess if I ever need to tow more I can just go back to 32s. The 35s I was going to get were to go on a set of Gladiator oem take-off wheels

 

[ShadowsPapa]

Frankly that's what I'd do if I wanted that "Jeep look" of larger tires. I'd buy take-offs with wheels AND tires and simply swap when I wanted to tow. In fact, I may just do that since I only tow 2 or 3 times a year! Buy a set of wheels and tires another member has removed - that will fit under a stock Overland but give bigger tires - do that for winter and around here driving and put the stock highway wheels and tires back when I want to haul my car.
Love that idea!

 

[Oscar Indy]

After speaking with my friend at Jeep the biggest difference between the max tow and Rubicons lower capacity is the tire size. Some is spring rate but he said the majority of it is the tires.
So you loose 600ish pounds for every 2in of tire size.

 

[WXman]

After speaking with my friend at Jeep the biggest difference between the max tow and Rubicons lower capacity is the tire size. Some is spring rate but he said the majority of it is the tires.
So you loose 600ish pounds for every 2in of tire size.

No offense, but your friend hasn't got a single clue what he's talking about. Tires are all stamped with a load rating. Size has nothing to do with it.

The factory tires on a JT Rubicon have a load rating of 2,755 lbs.

The factory tires on a JT with the Max Towing package have a load rating of only 2,469 lbs.

If the difference between the two trims were tires, the Rubicon would have a payload capacity of at least 572 more lbs.

But, in actuality, the real difference between the two is the coil springs used, and the curb weight. Rubicon and Max Tow both have identical GVWR, but the lighter curb weight of the Max Tow allows it to have better hauling/towing numbers, and the coil springs handle loading well.

 

[PyrPatriot]

No offense, but your friend hasn't got a single clue what he's talking about. Tires are all stamped with a load rating. Size has nothing to do with it.

The factory tires on a JT Rubicon have a load rating of 2,755 lbs.

The factory tires on a JT with the Max Towing package have a load rating of only 2,469 lbs.

If the difference between the two trims were tires, the Rubicon would have a payload capacity of at least 572 more lbs.

But, in actuality, the real difference between the two is the coil springs used, and the curb weight. Rubicon and Max Tow both have identical GVWR, but the lighter curb weight of the Max Tow allows it to have better hauling/towing numbers, and the coil springs handle loading well.

Thank you

 

[ShadowsPapa]

No offense, but your friend hasn't got a single clue what he's talking about. Tires are all stamped with a load rating. Size has nothing to do with it.

The factory tires on a JT Rubicon have a load rating of 2,755 lbs.

The factory tires on a JT with the Max Towing package have a load rating of only 2,469 lbs.

If the difference between the two trims were tires, the Rubicon would have a payload capacity of at least 572 more lbs.

But, in actuality, the real difference between the two is the coil springs used, and the curb weight. Rubicon and Max Tow both have identical GVWR, but the lighter curb weight of the Max Tow allows it to have better hauling/towing numbers, and the coil springs handle loading well.

Yes, but....... tire size can come into play when you run taller tires and thus change the final engine RPM to road speed number. Bigger tires means the engine has less advantage and has to work harder, generating more heat - taxing the already nearly maxed out cooling system on these. The grill was an internal struggle on these things, as was the front exposure to air getting in due to the thing already having been certified structure-wise. So it was a balancing act.
You need to keep the engine in the peak power band, and the transmission from working hard and running hot, cut shifting down, etc. - that all generates heat and according to one of those involved, heat was a major issue with the towing and payload capabilities. It was the final hurdle.
Taller tires on a vehicle where all else is exactly the same puts the engine itself at a disadvantage and would be akin to putting the 3.xx gear ratio in a max tow Jeep - it would take away some ability.
But you are of course right on that's not THE difference.
I looked at the dry weight differences and that's not all of it either because the numbers don't add up. Part of it, but not all - the math doesn't work out.
Anyway, the tires are a minor thing compared to the different springs and such - the Rubicon and Overland have their "niche" and are built for different things. It makes sense that the SPORT be the towing version.

In short you aren't going to put the Sport tires on the Overland or Rubicon and make them towing capable like the Sport.
There's spring RATE differences, vehicle weight differences (to stay within the AXLE ratings - and that's another issue- axles.... it's more complex than just one thing or another. I wonder about the axle bearing part numbers, for example. I've done my share of maintenance and found that two pickups of the same year and same level (3/4 ton compared to 3/4 ton) may take different AXLE bearings based on the towing and payload capabilities. Axle diameter, so much to consider.
I believe max tow has a different wattage fan system and thus requires that honking big capacity alternator. 240 amps is a lot of output for that small truck indicating to me that sucker kicks out some BTUs and requires hefty fans.
You can't convert one to the other by swapping a couple simple parts. Just doesn't work that way.

 

[PyrPatriot]

Yes, but....... tire size can come into play when you run taller tires and thus change the final engine RPM to road speed number. Bigger tires means the engine has less advantage and has to work harder, generating more heat - taxing the already nearly maxed out cooling system on these. The grill was an internal struggle on these things, as was the front exposure to air getting in due to the thing already having been certified structure-wise. So it was a balancing act.
You need to keep the engine in the peak power band, and the transmission from working hard and running hot, cut shifting down, etc. - that all generates heat and according to one of those involved, heat was a major issue with the towing and payload capabilities. It was the final hurdle.
Taller tires on a vehicle where all else is exactly the same puts the engine itself at a disadvantage and would be akin to putting the 3.xx gear ratio in a max tow Jeep - it would take away some ability.
But you are of course right on that's not THE difference.
I looked at the dry weight differences and that's not all of it either because the numbers don't add up. Part of it, but not all - the math doesn't work out.
Anyway, the tires are a minor thing compared to the different springs and such - the Rubicon and Overland have their "niche" and are built for different things. It makes sense that the SPORT be the towing version.

In short you aren't going to put the Sport tires on the Overland or Rubicon and make them towing capable like the Sport.
There's spring RATE differences, vehicle weight differences (to stay within the AXLE ratings - and that's another issue- axles.... it's more complex than just one thing or another. I wonder about the axle bearing part numbers, for example. I've done my share of maintenance and found that two pickups of the same year and same level (3/4 ton compared to 3/4 ton) may take different AXLE bearings based on the towing and payload capabilities. Axle diameter, so much to consider.
I believe max tow has a different wattage fan system and thus requires that honking big capacity alternator. 240 amps is a lot of output for that small truck indicating to me that sucker kicks out some BTUs and requires hefty fans.
You can't convert one to the other by swapping a couple simple parts. Just doesn't work that way.

And I am not wanting to convert a sport to a Rubicon, just want to get more performance off-road than a Sport, and more towing than a Rubicon offers. It seems there should be a sliding scale to this: 35s will drain this much towing/power, 37s will drain this much more but give this much better clearance, etc.

 

[ShadowsPapa]

I don't think you are going to find such a thing. and so much depends on what you will be towing. For example, me towing a car hauler at 4600-5000 would notice more difference in a tire change than someone towing a small camper or a boat or jet skis at say, 3000-4000 pounds. Some may make a change and suggest they don't really feel much difference at all, others may say it changed things a lot - wind resistance, height of the load - I see in the Jeep documents that there's even a spec for the "frontage" of the towed load - meaning they are considering the wind resistance that an enclosed trailer would offer vs. one that's open like mine.
I just don't think you are going to find a simple solution - but in the end, if I'm wrong I sincerely hope someone demonstrates that!!
I live to learn.........

 

[PyrPatriot]

I don't think you are going to find such a thing. and so much depends on what you will be towing. For example, me towing a car hauler at 4600-5000 would notice more difference in a tire change than someone towing a small camper or a boat or jet skis at say, 3000-4000 pounds. Some may make a change and suggest they don't really feel much difference at all, others may say it changed things a lot - wind resistance, height of the load - I see in the Jeep documents that there's even a spec for the "frontage" of the towed load - meaning they are considering the wind resistance that an enclosed trailer would offer vs. one that's open like mine.
I just don't think you are going to find a simple solution - but in the end, if I'm wrong I sincerely hope someone demonstrates that!!
I live to learn.........

That’s fair. I am just trying to make sure I dont booger up anything in my first jeep/truck. I ruined my Honda Element by overloading it, not knowing any better. Hoping to learn from folks with actual experience. There must be plenty of people who added larger tires and lifted their gladiators, I cant imagine that none of them didnt tow at least 50-65% of their Jeep’s rating.

 

[ShadowsPapa]

That’s fair. I am just trying to make sure I dont booger up anything in my first jeep/truck. I ruined my Honda Element by overloading it, not knowing any better. Hoping to learn from folks with actual experience. There must be plenty of people who added larger tires and lifted their gladiators, I cant imagine that none of them didnt tow at least 50-65% of their Jeep’s rating.

And I am following as who knows- I may some day want a bit more tire under mine. It's Iowa, we get snow, sometimes deep snow and I don't like moving it so drive through it and have a fairly long driveway, especially from my shop area. It's not my first "Jeep" or my first "Jeep truck" (had a Comanche) but will be the first of this sort - so I can't say I'd never have a bit of fun with it or want to make some changes.
I totally relate and get it. Besides, these are too expensive to screw up! LOL

 

[Oscar Indy]

My friend is the guy responsible for the capacity numbers. I'll take his word over yours. Shadows nailed it with the gearing. 560 pounds of trailer weight means little to springs when they only get a fraction of that in the form of tounge weight.

 

[ShadowsPapa]

Now I need to figure out this bit about 33, 35, 37 and so on. I am used to buying tires by rim size and profile - not height.
So when someone says a 33" tire - what the heck?
What "height" if that's what we are discussing is the STOCK Overland tire?
Say I put 33's on my Overland when I get it - what would be the difference?
I know of a full set of Goodyear Wrangler Duratrac tires on 17" wheels (I suspect they came off a Jeep Wrangler - haven't asked)
The guy says they'd be fine on a stock Overland with no lift at all. But I have no clue what my JT will come with so other than the aggressive tread (he says they are great in snow - he runs them on his Wrangler) I know nothing about the size differences.

 

[Oscar Indy]

Now I need to figure out this bit about 33, 35, 37 and so on. I am used to buying tires by rim size and profile - not height.
So when someone says a 33" tire - what the heck?
What "height" if that's what we are discussing is the STOCK Overland tire?
Say I put 33's on my Overland when I get it - what would be the difference?
I know of a full set of Goodyear Wrangler Duratrac tires on 17" wheels (I suspect they came off a Jeep Wrangler - haven't asked)
The guy says they'd be fine on a stock Overland with no lift at all. But I have no clue what my JT will come with so other than the aggressive tread (he says they are great in snow - he runs them on his Wrangler) I know nothing about the size differences.

It's easier than the metric crap because it's total height. A 33 is 33in diameter. So your overland has 31ish tires. A 33 will be 2 full inches taller.

 

[ShadowsPapa]

It's easier than the metric crap because it's total height. A 33 is 33in diameter. So your overland has 31ish tires. A 33 will be 2 full inches taller.

But that's where the confusion comes in - nowhere does the tire say "I'm a 33" tall tire". Nowhere on the Gladiator specs showing tire size for any of them, Overland included, does it say "these are 31" tires".
No, they say 18" rims, 255/70R15 so where the heck is anyone getting the DIAMETER out of that?
Looking at that - where does it say it's a 31" tire? Where does the guy that's saying the tires he has are 33" tall - where on the tire does it say 33" tall?

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