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Old 09-01-2016, 04:51 AM   #15
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Originally Posted by drdarrin View Post
The difference is that by upgrading the hitch, you have removed the weak link, as you so aptly pointed out, and probably haven't exceeded any of the Gross ratings on either the truck or trailer.
My point is, what is the difference between upgrading the hitch and then exceeding the Tow rating vs upgrading the tires and then exceeding the Axle rating?. Many people may perceive that both are equally ok.
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Old 09-01-2016, 07:30 AM   #16
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towing 5th vs trailer weight limits?

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Originally Posted by dayle1 View Post
My point is, what is the difference between upgrading the hitch and then exceeding the Tow rating vs upgrading the tires and then exceeding the Axle rating?. Many people may perceive that both are equally ok.


Neither is ok if you exceed any of the 5 gross ratings for your truck or trailer. But "tow rating" isn't one of them. Did you miss the fine print that says tow rating is an ESTIMATE and mutually exclusive of payload?

Perhaps a better comparison would be upgrading your 5er hitch from 15K to 20k. That doesn't increase any of your trucks capacities either but MAY increase what you can safely tow, assuming the hitch was a limiting factor. You still have to do the math.
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Old 09-01-2016, 07:50 AM   #17
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Neither is ok if you exceed any of the 5 gross ratings for your truck or trailer. But "tow rating" isn't one of them. Did you miss the fine print that says tow rating is an ESTIMATE and mutually exclusive of payload?
Which is exactly why you use one of the towing calculators I posted for each and every configuration your tow. It would be nice if there was an app for those.
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Old 09-01-2016, 08:22 AM   #18
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Originally Posted by drdarrin View Post
Which explains why a Ram with GVWR of 14,000, front GAWR of 5500, rear GAWR of 9750 and GCWR of 39100 has a max trailer weight rating of 31,210 lbs.
Tow rating is GCWR minus the empty weight of the tow vehicle, and ignores payload capacity, GAWRs and hitch capacity. So a tow rating of 31,210 pounds with GCWR of 39,100 simply means the tow vehicle can tow up to 31,200 pounds trailer only when the tow vehicle weighs 7,890 pounds or less - with hitch and driver and a full tank of fuel, but without the trailer.

In the real world with a tow vehicle that has tow rating of 31.200 pounds, if there is no weight in the tow vehicle except a full tank of fuel and a skinny driver, you can probably tow a wagon-style grain trailer that has almost no hitch weight and grosses 31,000 pounds without being overloaded.

But TTs average 13% tongue weight, and smaller 5ers average 17 to 18% kingpin weight, so tow ratings are severely overstated for RV trailers - because you will exceed the GVWR (and payload capacity) of the tow vehicle before you get close to the GCWR of the tow vehicle..
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Old 09-01-2016, 11:07 PM   #19
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The bottom line from what I understand is weight is weight. If some one has a ram 3500 6.7 hemi which is rated to tow 13k Really can not tow a TT or 5th difference n weight as weight is still weight when it comes down to it.
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Old 09-02-2016, 08:48 AM   #20
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There are two kinds of RV trailer weight = 1] the kind you pull and 2] the kind you carry.

GCWR indicates the max combined weight of a rig you can pull. Tow rating is GCWR minus the weight of the truck, so theoretically it's the max weight of a trailer you can pull with that tow vehicle. GCWR is accurate, but tow ratings are overstated because the manufacturers use the weight of the lightest vehicle they sell that meets the requirements of the GCWR (engine, transmission, axle ratio, cab/wheelbase, drivetrain, hitch weight rating) .

GVWR indicates the max weight you can carry on the tires of the tow vehicle, including hitch weight but not the weight of the trailer other than hitch weight. Payload capacity is GVWR minus the weight of the truck. GVWR is accurate, but payload capacity is overstated because the manufacturers use the weight of the lightest vehicle they sell that meets the requirements of the GVWR (tires, wheels, suspension, frame strength, braking capacity).

Almost all tow vehicles with single rear wheels (SRW) can pull more trailer weight than they can carry the hitch weight of that trailer.
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Old 09-02-2016, 10:23 PM   #21
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Spot on Smokey! This is why it seems silly to buy a 3500 or F350 SRW rather than DRW espically considering the cost is less than $1,500.
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Old 09-03-2016, 09:35 AM   #22
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Originally Posted by dayle1 View Post
My point is, what is the difference between upgrading the hitch and then exceeding the Tow rating vs upgrading the tires and then exceeding the Axle rating?. Many people may perceive that both are equally ok.
Many people are math challenged and logic challenged. They don't understand what "tow rating" means. Tow rating is not an engineered rating. It is simply GCWR minus the shipping weight of the tow vehicle, with nothing in the vehicle except a skinny driver and a full tank of fuel. And limited by the weight rating of the hitch. That's why the tow rating for a TT is often less than the tow rating for a 5er. 5er hitches are rated for a minimum of 15k and most are rated for 16k or more. But receiver hitches for towing a "bumper pull" trailer are usually rated for a lot less than 5er hitches. Some OEM receivers are rated for as little as 1,500 pounds, and most on half-ton pickups are rated for 5,000 pounds with a weight-carrying (WC) hitch and 10,000 pounds for a weight-distributing (WD) hitch.

GCWR is engineered. GCWR is the highest weight that can be pulled by the tow vehicle without exceeding any of the weight limits of the components of the vehicle. The primary components of GCWR are the power and torque of the engine, and the gearing. Gearing is relatively simple to change, so you can change the GCWR of any vehicle by changing the ring gear and pinion in the differential. Or if you are positive that the weight rating of the receiver hitch is the limiter to tow rating, then you can install a receiver with more weight limits and increase the tow rating up to the max of GCWR minus the weight of the vehicle.


Axle rating is a misnomer. It's gross axle weight rating (GAWR). It is not just the axle assembly, but is also based on the weight limits of all the components that make up the third member, including differential, axle shafts and bearings, tires, wheels and suspension. So to change the axle rating, you would have to change the component that is the limiter as to the GAWR. Hint: It's not the tires. It's not the wheels. And it's probably not the axle assembly. And if you're not a chassis engineer, you probably wouldn't have a clue as to what changes you would need to make to increase GAWR. But guaranteed that changing to heavier-duty tires will not change the GAWR on modern vehicles.
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Old 09-05-2016, 01:26 AM   #23
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Well said.
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Originally Posted by SmokeyWren View Post
Many people are math challenged and logic challenged. They don't understand what "tow rating" means. Tow rating is not an engineered rating. It is simply GCWR minus the shipping weight of the tow vehicle, with nothing in the vehicle except a skinny driver and a full tank of fuel. And limited by the weight rating of the hitch. That's why the tow rating for a TT is often less than the tow rating for a 5er. 5er hitches are rated for a minimum of 15k and most are rated for 16k or more. But receiver hitches for towing a "bumper pull" trailer are usually rated for a lot less than 5er hitches. Some OEM receivers are rated for as little as 1,500 pounds, and most on half-ton pickups are rated for 5,000 pounds with a weight-carrying (WC) hitch and 10,000 pounds for a weight-distributing (WD) hitch.

GCWR is engineered. GCWR is the highest weight that can be pulled by the tow vehicle without exceeding any of the weight limits of the components of the vehicle. The primary components of GCWR are the power and torque of the engine, and the gearing. Gearing is relatively simple to change, so you can change the GCWR of any vehicle by changing the ring gear and pinion in the differential. Or if you are positive that the weight rating of the receiver hitch is the limiter to tow rating, then you can install a receiver with more weight limits and increase the tow rating up to the max of GCWR minus the weight of the vehicle.


Axle rating is a misnomer. It's gross axle weight rating (GAWR). It is not just the axle assembly, but is also based on the weight limits of all the components that make up the third member, including differential, axle shafts and bearings, tires, wheels and suspension. So to change the axle rating, you would have to change the component that is the limiter as to the GAWR. Hint: It's not the tires. It's not the wheels. And it's probably not the axle assembly. And if you're not a chassis engineer, you probably wouldn't have a clue as to what changes you would need to make to increase GAWR. But guaranteed that changing to heavier-duty tires will not change the GAWR on modern vehicles.
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Old 09-05-2016, 06:19 AM   #24
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GCWR is engineered. GCWR is the highest weight that can be pulled by the tow vehicle without exceeding any of the weight limits of the components of the vehicle. The primary components of GCWR are the power and torque of the engine, and the gearing. Gearing is relatively simple to change, so you can change the GCWR of any vehicle by changing the ring gear and pinion in the differential.
Certainly there is a component limitation but GCWR is also engineered to a performance criteria that is unknown to the owner and not consistent across brands/years. Hence a ring/pinion change or tire diameter change alters GCWR or farmers/ranchers exceed stated GCWR for many years but at reduced speeds or performance levels.

Quote:
Originally Posted by SmokeyWren
Axle rating is a misnomer. It's gross axle weight rating (GAWR). It is not just the axle assembly, but is also based on the weight limits of all the components that make up the third member, including differential, axle shafts and bearings, tires, wheels and suspension. So to change the axle rating, you would have to change the component that is the limiter as to the GAWR. Hint: It's not the tires. It's not the wheels. And it's probably not the axle assembly. And if you're not a chassis engineer, you probably wouldn't have a clue as to what changes you would need to make to increase GAWR. But guaranteed that changing to heavier-duty tires will not change the GAWR on modern vehicles.
I agree this is a good general explanation but minimal investigation reveals that many times tires are the limiting issue with GAWR, at least with modern diesel PUs, where the only PN differences between 3/4 and 1 ton are tires, wheels and spring pack. But yes an owner cannot make any change that legally increases GAWR.
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