Why you SHOULD be able to tow more than sticker outside of the mountains

[PyrPatriot]

I came to this realization posting in another thread.

Just spitballing. Have no idea if this is the right thought process to the topic so posting for more learned folk to chime in


The towing limitation is based on weight, cooling being the thing to overcome. The rating, as far as I can tell, is under the SAE J2870 standard of towing determination (revised in 2016 and again in 2020, for what it's worth, interesting to note but I don't know the difference because I'm not paying $83 to access the publication https://www.sae.org/standards/content/j2807_202002/)

Here are the main test methods trucks would be measured on as per J2807:

• Cooling capability on a long highway upgrade modeled on the Davis Dam grade on Arizona SR 68 at 100 degrees temperature outside;
  • The Davis Dam Grade Arizona State Route 68 is a stretch of road that starts in the Davis Dam area of the Colorado River, close to Laughlin, Nevada, and Bullhead City, Arizona, with an elevation of just about 550 feet. This stretch of highway travels through the Black Mountains and climbs to Highway 93 near Kingman, Arizona. The section used for the SAE J2807 Highway Gradeability Test starts just past the intersection of SR 68 and Highway 95 outside of Laughlin and climbs to more than 3,500 feet (3000ft change) in just 11.4 miles.
    
  • In addition to a hot climate outside the truck, the test requires the air conditioning system to be set at maximum cold, with outside air selected (not recirculating) and the fan running at full blower speed.
• Launch and acceleration performance on a level road and a 12 percent upgrade;
  • a truck must be able to launch and travel 16 feet (5 meters) uphill, five times in a row, in 5 minutes or less. Then, the truck and trailer has to be able to complete the same test while launching up a 12 percent grade in Reverse.
• A truck-and-trailer combination must be able to drive at 40 mph (35 mph for dualies) and never drop below that speed until the end of the test segment at the peak of Union Pass.
  
• Combined handling performance – understeer and trailer sway;
  • Understeer (the opposite of fishtailing) is measured at three different levels of Front Axle Load Restoration (FALR), which is a calculation of how much the load on the front axle changes.
• Combined braking performance – stopping distance and parking brake-hold on grade; and
  • Combos with a maximum tow rating of more than 3,000 pounds are required to stop completely from 20 mph in 80 feet or less. During this stop test, the trailer must remain within an 11.5-foot-wide lane throughout the entire stop. In addition to the active testing, the parking brake must be able to hold the truck and trailer firmly in place both upward and downward on a 12 percent grade when it is at the maximum GCWR.
• Structural performance for the vehicle and hitch or hitch receiver.

It assumes

• For light-duty full-size pickups (GVWR < 8,500 lbs.), SAE J2807 assumes that the tow vehicle includes any options with higher than 33 percent penetration;
• It assumes there is both a driver and passenger in the vehicle, each weighing 150 pounds;
• It assumes that tow vehicles also include up to 70 pounds of aftermarket hitch equipment (where applicable); and
• For conventional trailer towing, SAE J2807 assumes that 10 percent of the trailer weight is on the tongue.

Citations
https://jalopnik.com/the-engineering-behind-the-jeep-gladiators-tow-rating-1833657453
https://jalopnik.com/what-is-sae-j2807-what-does-it-mean-for-trucks-1593305929
http://www.trucktrend.com/how-to/towing/1502-sae-j2807-tow-tests-the-standard/

The JT is a GVRW of 12,500lbs so it fits the requirement. Assuming 300lbs of occupants means that weight can be disregarded from payload deducting from towing capacity. So for non-12% grade towing I'll be fine with my Max Tow, family and gear, and a 7000lb trailer. Will it struggle? probably. But the point is when you consider HOW FCA determined their claimed towing numbers you see that without the grueling conditions the JT Max Tow is capable of MUCH more towing, I'd estimate 8000-9000lbs if you have only hills to go over and it's just you. Add 20% towing capacity by eliminating the 12% grade, and maybe another 10% if it isn't sweltering hot outside and you don't have Max A/C on. For the Sport Max Tow that is 9,945, and of course without a 150lb passenger that's 10,095lbs of towing. In theory. I'm not gonna try it. The hitch is only a class 4 (10k lbs) and I'll stay well within the limits there. But now I don't feel so bad towing 8000lbs on my own, or fully utilizing the truck by loading my family and gear up, and maxing out payload with a 7500lb trailer.

Edit: keeping the GCWR of 12,500lbs is important. That limit, like the axle weight rating, is mechanical and not based on tricks. 12,500-7650+300 = 5150 means your gross vehicle weight needs to be 5150lbs. I think the JT sports are around 4700lbs. So 5150lb of GCVWR left, less 4700 = 450lbs. so you can have that 7650lb trailer and you in the vehicle, that's it. Because 10% of the tongue weight is 765lbs, which is 300lbs over the payload at that point.


Something doesn't add up

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[futzin']

But now I don't feel so bad towing 8000lbs on my own, or fully utilizing the truck by loading my family and gear up, and maxing out payload with a 7500lb trailer.

You may not feel bad now, but you will if you actually do it.

 

[PyrPatriot]

You may not feel bad now, but you will if you actually do it.

wasnt there a member here who overloaded his JTR by 700lbs and over towed by 1000lbs over a mountain and did just fine?

 

[futzin']

I have towed 9K before (with a truck rated for 10K). No way I'd even consider 8+ with any current JT. Been towing trailers for roughly 25 years, albeit most 6K-ish. Used to tow 6K with a Suburban rated for 6K; neither I nor the truck liked it. Maxed out is right! Never again . . .

 

[PyrPatriot]

I have towed 9K before (with a truck rated for 10K). No way I'd even consider 8+ with any current JT. Been towing trailers for roughly 25 years, albeit most 6K-ish. Used to tow 6K with a Suburban rated for 6K; neither I nor the truck liked it. Maxed out is right! Never again . . .

thank you for your input. This is exactly why I posted my thoughts on the subject, to elicit response from those with more experience

 

[futzin']

I'm not the ideal person to expound on towing; I like a certain amount of cushion when towing. For example, for my purposes I'm considering 5K about the max for a JTR. I wouldn't tow that if the JTR max was 5K. Others have different expectations/comfort levels/depth of pockets for repairs.

That being said, if I towed 5K with gear in truck and found it comfortable, then I might run up to 6K or so without gear but that would prolly tap me out. Just my take. There are plenty of guys who'll tell tales of towing crazy weights with 4 cyl. Rangers or whatever.

 

[Professor57]

100 degrees C temperature outside

Uh, water boils at 100 degrees C. I hope they mean 100 F!

 

[PyrPatriot]

Uh, water boils at 100 degrees C. I hope they mean 100 F!

You know, the article did not specify, I put it in as I was typing because of my science background. Given the American article, it is likely F. C has been removed.

That said, 100C is 212F, and isn't normal engine/transmission temperature 195-212F?

 

[bgenlvtex]

Many, many, many, too many variables to give an empirical evaluation and resulting hard and fast number.

All of that means nothing if you are going to tow for any appreciable distance.

7000lbs for a 100 miles, you'll be tired of that before you get back.

7000 lbs for 3000 miles? You'll never do that again.

Manufacturer tow ratings are proprietary and largely unsubstantiated numbers designed to sell something to someone who has no idea what he is buying. They are only slightly more than entirely meaningless.

 

[PyrPatriot]

Many, many, many, too many variables to give an empirical evaluation and resulting hard and fast number.

All of that means nothing if you are going to tow for any appreciable distance.

7000lbs for a 100 miles, you'll be tired of that before you get back.

7000 lbs for 3000 miles? You'll never do that again.

Manufacturer tow ratings are proprietary and largely unsubstantiated numbers designed to sell something to someone who has no idea what he is buying. They are only slightly more than entirely meaningless.

Possibly. My biggest takeaway is what the Jeep CAN do. Up until now the "rule of thumb" was to tow only 60-70% of the tow rating if going over anything but a short trip. That mean about 5000lbs for the Max Tow. But if the JT can actually tow 9500lbs under gentler conditions, well then 6000-7000 seems MUCH more reasomable

 

[bgenlvtex]

Possibly. My biggest takeaway is what the Jeep CAN do. Up until now the "rule of thumb" was to tow only 60-70% of the tow rating if going over anything but a short trip. That mean about 5000lbs for the Max Tow. But if the JT can actually tow 9500lbs under gentler conditions, well then 6000-7000 seems MUCH more reasomable

The manufacturers decision making flow chart goes like this :

How much can we advertise this truck to tow without it self destructing?

Can we self certify that using the SAE standard?

OK good that's it.


My point is entirely that as you cross that 5k mark, driver effort will increase exponentially to the point where it won't matter IF it will tow it, because you won't want to tow it a second time, again assuming it is for any appreciable distance.

 

[PyrPatriot]

ou won't want to tow it a second time,

Explain, please. Is it from frustration of the vehicle struggling? Going slow? What makes it so bad?

 

[bgenlvtex]

Explain, please. Is it from frustration of the vehicle struggling? Going slow? What makes it so bad?

Once the weight of the towed item exceeds the weight of the tow vehicle, the operator effort goes up substantially on vehicles not specifically designed to mitigate that effort.

This is one of those cases where you can study numbers to your hearts content, but when you try to apply that numerically supported logic you find out there are intangible modifiers to your numerically supported logic.

Or in more direct terms tow ratings are largely a bunch of horse shit.

For more years than I care to consider I when given the choice have applied the 60% of tow rating rule. That rule is proprietary, unsupported my manufacturer ratings, and is based entirely on experience. I'm not telling you it is an absolute or correct for you, only what I have learned and will continue to apply.

The commute between my two addresses is a little over 4k miles. If I can't keep my trailer significantly under 4k pounds, I'll scrap the project entirely and move to a different tow vehicle (Power Wagon).

 

[PyrPatriot]

I think this article says just because you should be ABLE to doesn't mean you should DO it

https://auto.howstuffworks.com/auto...pacity/information/truck-towing-capacity1.htm
When you ask your truck to pull more than it was meant to -- exceeding its towing capacity -- a number of things start to happen: The brakes begin to fade, the added weight contributes to tire failure, and the extra work required of your engine causes it to overheat, which, in turn, overloads the drivetrain and shortens the life of your transmission. Although you may not see the effects of exceeding towing capacity at first, the gradual wear and tear will lead to eventual failure. The best case scenario is repeated trips to the repair shop; the worst is a major wreck...the extra weight pulling on the back of your vehicle significantly hampers your braking ability and steering control. When the back of your truck is loaded down, the front tires come up, causing them to lose some traction with the road. Without those front tires firmly on the ground, you'll definitely see a negative impact on your stability and handling. Your truck's brakes, which were designed to stop a limited amount of weight, will either take much longer to slow the vehicle down in an emergency or they simply won't work at all.


For me, I am happy knowing that if I need to try and yank a 9000lb vehicle out of a ditch, I won't destroy my JT doing so. Or if I need to tow at GCVR (900lbs loaded truck + 6250lbs trailer) I should be fine and not worry about the extra extra wear because the JT was designed to do more than that

Edit: keeping the GCWR of 12,500lbs is important. That limit, like the axle weight rating, is mechanical and not based on tricks. 12,500-7650+300 = 5150 means your gross vehicle weight needs to be 5150lbs. I think the JT sports are around 4700lbs. So 5150lb of GCVWR left, less 4700 = 450lbs. so you can have that 7650lb trailer and you in the vehicle, that's it. Because 10% of the tongue weight is 765lbs, which is 300lbs over the payload at that point.


Something doesn't add up. Does the GCVWR include a 150lbs driver and 150lb passenger like the test does?


12500 (GCVWR) -6250 (GVWR) = 6250lbs. So 1500lbs payload at best (for simplicity) means 735lbs of payload left with a 7650lb trailer. Looks like it's just the family in the truck. ALL the gear goes in the trailer!

 

[robertm55]

I have towed heavy trailers in the past. I always had a 2500 Silverado, or at minimum 1500 ram until now.
When I was purchasing my new travel trailer it was 2 months AFTER I purchased my Rubicon gladiator. That being the case, I decided that I would not get any trailer with a dry weight over 5000 lb.
Figure fully loaded trailer (water,gear etc.) Truck with two adults and two dogs would still keep me at a very comfortable weight.
All that said, I have pulled it over 12000 miles so far. Always very comfortable, no issues whatsoever (weight transferring hitch and properly adjusted brake controller).
I would not ever try to pull a 9000 lb trailer with my jt. Just not worth it.
I would definitely be afraid of crosswinds and emergency manuevers.

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