Class A Towing capacity

Lbligh, I am curious to know what the criteria is for any of the particular load limits? Is it a wear limit? Is it a stress limit, where if exceeded, it will immediately have catastrophic failure?

A perfect example would be my front differential. It is a Dana 70. If you look at the specs, it gives 2 numbers. One is a continuous operation and the other is a peak limit. Basically what those numbers mean is that the differential is expected to last X amount of miles if a continuous load of 2500 ft-lbs. It is rated for a peak torque load of 7000 ft-lbs. Basically if you exceed the peak torque, you will break teeth. That means you can exceed the continuous load rating and not break anything, but you will shorten the life. So if you use this axle in a towing situation, the tow rating will be based on the expected average torque load, because they want to get decent wear. So if you exceed the tow rating, what happens? NOTHING, except you will probably slightly shorten the life of the differential. So in this single example of one component, in this specific case, exceeding the tow rating is not catastrophic.

That is what tow rating are. If you have a 5000 lbs tow rating, and you tow 5001 lbs, does that mean you are taking a serious chance at causing a problem? Lets not be silly. Ratings are based on worse case scenario. IF you are more cautious about how you treat the vehicle, you can compensate for the limits of a rating up to a point.

jwoodie wrote:

lbligh wrote:

jwoodie wrote:
Does anybody here believe that 5,000 or 10,000 pound tow ratings are the result of an exact mathematical calculation? These are obviously general guidelines with a built in fudge factor. Otherwise, slight variations during the manufacturing process would result in some failures even when below the "maximum tow rating."

I am not suggesting that these rating be ignored, only that they be taken with a grain of salt when evaluating the towing capability of your rig. For example, dead tongue weight, weight distributing and four-down towing hitches are drastically different towing propositions, as are terrain, elevation, braking capacity and driver experience.

That being said, I would not greatly exceed the specified ratings for fear of voiding warranty and/or insurance coverage.

Indeed a lot of engineering and "exact mathematical calculation" goes into rating capacities including GCWR. Statements like "these are obviously general guidelines with a built in fudge factor" sound ridiculous. Folks that run around and ignore ratings sure make a good argument to require CDL licensing standards to all motorhomes.

Now... if someone would like to see a good snapshot of just how ratings can change depending on various factors (axle capacities etc.) take a few minutes and visit the link below. A very good condensed piece of information to educate some who may want to learn something. The detailed specification information starts on page six of the file. While these specifications are for the 2014 Ford F53 chassis, the same kind of engineering goes into any motorhome chassis or commercial vehicle.

https://www.fleet.ford.com/resources/ford/general/pdf/brochures/Class_A_brochure-2014_LoRes.pdf

Safe travels.

Amazing how these mathematical calculations come out to exactly 5,000 or 10,000 pounds. Statistically impossible, of course.

I am not sure if you have a problem with math/numbers or reading or possibly both? Or maybe you didn't even bother to look at the documents or possibly don't understand them? Out of the six examples shown, only one came in with a 5,000 lb number. None had 10,000 lbs. In fact, the range was 4,000 lbs to 7,000 lbs. Maybe you need to look again?

Safe travels.

lbligh wrote:

jwoodie wrote:
Does anybody here believe that 5,000 or 10,000 pound tow ratings are the result of an exact mathematical calculation? These are obviously general guidelines with a built in fudge factor. Otherwise, slight variations during the manufacturing process would result in some failures even when below the "maximum tow rating."

I am not suggesting that these rating be ignored, only that they be taken with a grain of salt when evaluating the towing capability of your rig. For example, dead tongue weight, weight distributing and four-down towing hitches are drastically different towing propositions, as are terrain, elevation, braking capacity and driver experience.

That being said, I would not greatly exceed the specified ratings for fear of voiding warranty and/or insurance coverage.

Indeed a lot of engineering and "exact mathematical calculation" goes into rating capacities including GCWR. Statements like "these are obviously general guidelines with a built in fudge factor" sound ridiculous. Folks that run around and ignore ratings sure make a good argument to require CDL licensing standards to all motorhomes.

Now... if someone would like to see a good snapshot of just how ratings can change depending on various factors (axle capacities etc.) take a few minutes and visit the link below. A very good condensed piece of information to educate some who may want to learn something. The detailed specification information starts on page six of the file. While these specifications are for the 2014 Ford F53 chassis, the same kind of engineering goes into any motorhome chassis or commercial vehicle.

https://www.fleet.ford.com/resources/ford/general/pdf/brochures/Class_A_brochure-2014_LoRes.pdf

Safe travels.

Amazing how these mathematical calculations come out to exactly 5,000 or 10,000 pounds. Statistically impossible, of course.

Even though my 35' DP has a 10,000 pound hitch it is transmission limited to 5,000lb unless you believe that the Allison transmission is conservatively rated. Some of the new Freightliners have the 2500 Allison (mine is the 2100) and are rated to pull quite a bit more. At least I have trailer truck running gear so control has never been an issue, I don't even feel the trailer back there. I do have a good brake controller and use the trailer brakes. Gassers typically have a lot more rear overhang and will bounce your trailer more on bumps. Keep that in mind if you have a fragile load.

jwoodie wrote:
Does anybody here believe that 5,000 or 10,000 pound tow ratings are the result of an exact mathematical calculation? These are obviously general guidelines with a built in fudge factor. Otherwise, slight variations during the manufacturing process would result in some failures even when below the "maximum tow rating."

I am not suggesting that these rating be ignored, only that they be taken with a grain of salt when evaluating the towing capability of your rig. For example, dead tongue weight, weight distributing and four-down towing hitches are drastically different towing propositions, as are terrain, elevation, braking capacity and driver experience.

That being said, I would not greatly exceed the specified ratings for fear of voiding warranty and/or insurance coverage.

Indeed a lot of engineering and "exact mathematical calculation" goes into rating capacities including GCWR. Statements like "these are obviously general guidelines with a built in fudge factor" sound ridiculous. Folks that run around and ignore ratings sure make a good argument to require CDL licensing standards to all motorhomes.

Now... if someone would like to see a good snapshot of just how ratings can change depending on various factors (axle capacities etc.) take a few minutes and visit the link below. A very good condensed piece of information to educate some who may want to learn something. The detailed specification information starts on page six of the file. While these specifications are for the 2014 Ford F53 chassis, the same kind of engineering goes into any motorhome chassis or commercial vehicle.

https://www.fleet.ford.com/resources/ford/general/pdf/brochures/Class_A_brochure-2014_LoRes.pdf

Safe travels.

Even though my 35' DP has a 10,000 pound hitch it is transmission limited to 5,000lb unless you believe that the Allison transmission is conservatively rated. Some of the new Freightliners have the 2500 Allison (mine is the 2100) and are rated to pull quite a bit more. At least I have trailer truck running gear so control has never been an issue, I don't even feel the trailer back there. I do have a good brake controller and use the trailer brakes. Gassers typically have a lot more rear overhang and will bounce your trailer more on bumps. Keep that in mind if you have a fragile load.

Does anybody here believe that 5,000 or 10,000 pound tow ratings are the result of an exact mathematical calculation? These are obviously general guidelines with a built in fudge factor. Otherwise, slight variations during the manufacturing process would result in some failures even when below the "maximum tow rating."

I am not suggesting that these rating be ignored, only that they be taken with a grain of salt when evaluating the towing capability of your rig. For example, dead tongue weight, weight distributing and four-down towing hitches are drastically different towing propositions, as are terrain, elevation, braking capacity and driver experience.

That being said, I would not greatly exceed the specified ratings for fear of voiding warranty and/or insurance coverage.

Daveinet wrote:
Actually Lbligh, you did not read the post you quoted thoroughly. He just stated the trans was a big piece of the towing capacity, not that the trans size was exclusive limitation. We do know the trans is the only limit in some situations. obviously not all, but if someone did research on their particular coach, they could find that out. I think the point of the post was give an example, not make a universal conclusion.

I believe that maybe you need to go back and read the post? I am sorry, but the post specifically stated "the hitch rating AND the transmission" were in the posters view the two items most responsible for the rating. Having an MH3000 transmission may indeed be one part of the chassis manufacturers criteria in setting GCWR capacity. The point is that having an MH3000 transmission does not immediately provide for any GCWR rating. Clearly a coach could be equipped with the MH3000 and have the manufacturer set a GCWR that would limit the capacity well under 10,000 lbs. Folks simply need to understand how to read their Federal certifications labels and abide by them. Thinking that a visit to their local welding shop to in their mind upgrade their towing capacity is a fools dream and places others in jeopardy.

Safe travels.

Actually Lbligh, you did not read the post you quoted thoroughly. He just stated the trans was a big piece of the towing capacity, not that the trans size was exclusive limitation. We do know the trans is the only limit in some situations. obviously not all, but if someone did research on their particular coach, they could find that out. I think the point of the post was give an example, not make a universal conclusion.

ferndaleflyer wrote:
Ibligh is just exactly what I was referring to----he knows it all and has probably done none of it. On the other hand I have been doing it for over 40 years I guess, usually over 30,000 or so miles a year, never had an accident, (no accident when ball broke) never a citation, and never had any problems related to towing happen to the DP or the trailer. But from my experience in the past few years with this unit it tows up mountains, stops when asked to, and does just as I expect it to. Anyone can have an accident no matter how hard you try to avoid it.....Maybe you should walk through the pits at an automobile race and take a look at what is towing what especially here in NC where we are allowed to be 90ft long. Oh and some hitches are rated at 20,000lbs. That is 10 tons!!!!!!

Maybe you were not paying attention? As I have said here, I have been in the truck business for over 40 years. I was the Director of operations with a truck fleet in excess of 11,000 units. So I guess I have done it and have been paid well to do it. You might want to watch what you say when you have no idea on what you are talking about? Just a thought...