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Old 01-14-2013, 08:28 PM   #1
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Confused about tow ratings

This question is probably answered somewhere but I can't find it. How can you have a safety margin of 680 lbs on truck front axle and 800 on rear axle and be over max on gross vehicle weight by 420 pounds. I assume there is a simple explanation but I can't figure it out. Thanks.
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Old 01-14-2013, 10:03 PM   #2
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Rogerl,
The GVWR is not figured like on the class 8 trucks, which is the sum of the GAWR's. On pickups and some medium duty trucks (like the F550 Fords) the sum of the GAWR's are greater than the GVWR. It is confusing, but that is the way the industry is rating the pickups. Hope this helps, I know it is not a thorough explanation, but it is all I know.
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Old 01-14-2013, 10:10 PM   #3
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Same way on my F-250, 9800lb GVWR but going by the axle ratings I'd have over 11,000lbs. I'm guessing it has to do with braking/handling and a healthy safety margin requested by the corporate lawyers.
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Old 01-14-2013, 10:42 PM   #4
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Same way on my F-250, 9800lb GVWR but going by the axle ratings I'd have over 11,000lbs. I'm guessing it has to do with braking/handling and a healthy safety margin requested by the corporate lawyers.
I am licensed in my province for the total of both axle rating. More then my boddys pre 2005 duellies.
With the 14000 lbs tag on the unit puts it very close to a total of 26k lbs.
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Old 01-14-2013, 11:03 PM   #5
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All good points.

However the newer gen 2500 3500 trucks GVWR is comming close to the sum of the GAWRs just as our bigger class trucks.

I see many F350 SRW GVWRs just a couple of hundred pound over the sum of the GAWRs. Same with a couple of the F250 models.

Also GM 2500/3500 GVWRs are close to the sum of the axle ratings. Ram just released their '03 Ram Body Service Guide weights and payload specs today but with their higher RAWR numbers IMO they will be no different than GM or Ford in that respect.

In many cases using GVWR to figure loads on the rear axle, is over loading the rear axle on certain models.
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Old 01-15-2013, 06:50 PM   #6
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Quote:
Originally Posted by daveshan View Post
Same way on my F-250, 9800lb GVWR but going by the axle ratings I'd have over 11,000lbs. I'm guessing it has to do with braking/handling and a healthy safety margin requested by the corporate lawyers.
Engine size (HP and torque) also has a great impact on towing specs.
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Old 01-16-2013, 12:34 PM   #7
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Quote:
Originally Posted by Rogerl
Confused about tow ratings
Yep, you're confused.

Your topic title is tow ratings, but your questions involve weight ratings (GAWR and GVWR). Not the same thing.

You should go by the GVWR of the tow vehicle when matching tow vehicle to trailer. On pickups and vans and SUVs, you cannot add GAWRs and come with GVWR. If you never exceed the GVWR of the tow vehicle, you will only rarely exceed the front or rear GAWRs - never on a Ford but maybe on some lesser brands.

For RV trailers, the front GAWR is rarely a concern. The rear GAWR is not really a concern either, because if you will almost always exceed the GVWR before you get close to the rear GVWR of the tow vehicle.

Example: 2012 F-150 4x2 SuperCrew with 6.5' bed:
CAT scale said:
Steer axle = 3360 (FGAWR = 3750)
drive axle = 3840 (RGAWR = 3850)
-----------------
GVW = 7,200 (GVWR = 7100)
===================

So I was slightly overloaded over the GVWR, but not overloaded over either the front or rear GAWR.
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Old 01-16-2013, 01:21 PM   #8
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The manufacturers provide a GVWR for multiple reasons but mostly to provide users with a safe load capacity for the cars and trucks as they leave the factory in their stock configuration. Usually the limiting factor is the load capacity of the stock tires provided by the factory.

With even with a "super duty" truck its E rated tires are at most 3200@80 PSI for a rear load maximum of 6400 lbs. minus the 2700 lb. rear weight of the truck for a payload rating of 3700 lbs. in the bed. Tires and rims can be changed and in so doing either increase the safe payload capacity or seriously decrease it. So the factory weight ratings provide a safe zone for operation with a new and unmodified truck only.

For towing purposes the manufacturers' GCWR is a more useful measure as it takes into account the limitations of the engine and its systems (lubrication and cooling) and the transmission, drive train, axles, differential gears, frame, and suspension, which need to handle the working loads generated by moving the tow vehicle and its passengers and the towed trailer and its load, and the safe working capacity of the vehicles braking components. The only way to safely increase this value for hauling is to change the gears in the differential(s).

For example a current year GM truck with the gas V8 engine and 4.10 gears has a 25% higher tow rating and GCWR than the same truck with 3.73 gears. Changing the gears from 3.73 or taller gearing will increase the weight that can be towed without reducing the life of the truck's engine and transmission.

Easy enough to see how this plays out in the truck wars as each manufacturer vies to claim the king of the mountain title with the greatest GCWR. Note the changes made from the prior year's truck with regard to the engine, transmission, cooling system, and in particular to the truck's frame and to the size of its brakes.

The rear end itself of a Ford or Ram or GM 3/4 truck has a axle and wheel bearing capacity of more than 9700 lbs. and and that would enable a theoretical payload of up to 7,000 lbs., IF the rims and tires could handle the load. Easiest way to insure that they can is to double the number of rims and tires at the rear of the truck and enlarge the rear fenders, i.e. a "Dooley". At that point the weak link becomes the leaf springs and so more are added to turn the truck into a "1-ton" pickup.
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Old 01-16-2013, 01:24 PM   #9
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Nothing that the owner can do changes the GVWR, GAWR or GCWR ratings that the manufacturer applied to a particular vehicle. One can put 19.5" duallies on a 4 cylinder Ford Ranger, but the GVWR/GAWR sticker in the driver's door jamb isn't changed a bit.

It's really pretty simple. Why not buy the right truck for the job to begin with, or buy a towable RV that's within ALL the manufacturer's ratings of the truck?

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Old 01-16-2013, 10:56 PM   #10
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Nothing that the owner can do changes the GVWR, GAWR or GCWR ratings that the manufacturer applied to a particular vehicle. One can put 19.5" duallies on a 4 cylinder Ford Ranger, but the GVWR/GAWR sticker in the driver's door jamb isn't changed a bit.

It's really pretty simple. Why not buy the right truck for the job to begin with, or buy a towable RV that's within ALL the manufacturer's ratings of the truck?

Rusty
I can and my truck a 3/4 ton is licenced to carry more load then a pre 2005 F350 that my 2 friends own. They have advized me to lower it to save on registration but no way I need every lbs. My RVs do not load the tires enough to be concern but Ford springs are for ride so I had to add supporting plies. They were added by previous owner, I just left it that way and it is just a bit stiffer then previous GM.
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Old 01-16-2013, 11:00 PM   #11
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Originally Posted by Ray,IN View Post
Engine size (HP and torque) also has a great impact on towing specs.
As does the transmission rating.
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Old 01-17-2013, 04:46 AM   #12
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I can and my truck a 3/4 ton is licenced to carry more load then a pre 2005 F350 that my 2 friends own. They have advized me to lower it to save on registration but no way I need every lbs. My RVs do not load the tires enough to be concern but Ford springs are for ride so I had to add supporting plies. They were added by previous owner, I just left it that way and it is just a bit stiffer then previous GM.
Licensing it for X or X + 10,000 lbs doesn't change the manufacturer's ratings for the truck. Neither did the spring modifications. What it's licensed for and what the manufacturer rated it for are two entirely different subjects. You just paid more money to the state (or province, in your case) for permission to place more weight on their roads. Your driver's door sticker didn't change one iota.

I might be able to license that Ford Ranger I spoke of for 30,000 lbs GCW and 15,000 lbs GVW, but that doesn't make it one bit more mechanically capable of performing the work.

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Old 01-17-2013, 09:35 PM   #13
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Caissiel didn't say he had his truck registered at those high GCW so why bring it up. What you describe would be a illegal commercial registration anyway so why make that silly point. IMO you don't want to go there.

In some states and provinces a truck owner is required to register a private use truck at a GVWR/or GVW or tonnage or some type of weight. And no its not a commercial thing.

Many states as my state has no registered weight requirement for a private use truck. Were simply allowed to carry weight up to the sum of the GAWRs/tire caps (RAWR in particular) and pull whatever weight we feel comfortable pulling.

In BC for example a private use truck is required by law to have a registered GVWR. It may be the truck makers GVWR or the sum of the truck makers GAWRs as caissiel mentioned.

Now about GCWR. There is no GCWR identified/placarded/certification placard on a truck. A simple gear change/engine swap/tranny swap/etc by the owner can change a trucks GCWR.

The only certified weights on our trucks are GVWR and the GAWRs.
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Old 01-18-2013, 04:24 AM   #14
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Caissiel didn't say he had his truck registered at those high GCW so why bring it up.
Because some states require non-commercial trucks to be registered for a GVW and others require registration for a GCW (combined weight of truck and whatever it's towing). My point is, and remains, that the ability to register a truck with the state/province for a particular GVW or GCW has nothing whatsoever to do with the manufacturer's ratings or actual capabilities of that particular truck.

My point regarding the Ford Ranger is that upgrading the wheels/tires or even the rear axle has done nothing insofar as the truck's frame, drivetrain, cooling capacity, etc. to increase their capabilities. Therefore, the statement by some that the LEO is merely going to look at the tire ratings and determine weight capability from the sum of those misses the point that the truck's actual load carrying (or, for that matter, towing) capabilities are a function of far more than just its tire ratings.

As I said, if one is buying a truck, why not buy one that is rated by the manufacturer for the job at hand? Why in the world would one spend the money on a truck that is going to operate over its GVWR, rear axle GAWR or GCWR from the git-go? Get the right tool for the job.

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