Diesel Place banner

Towing calculations

5K views 49 replies 8 participants last post by  fvstringpicker 
#1 ·
I have a 2004 GMC Sierra 2500HD 4x4 crew cab short box with a 6.6L I am looking at new trailer so and I need to know the capacity of my truck. I made the following chart based on specs and actual weights measured.

Please look at it and add your two cents. Some "advice" I have been given would suggest I can haul a trailer twice as heavy as my truck, that can't be right.
 

Attachments

See less See more
1
#38 ·
I found this on the California dmv site:

(c) The maximum wheel load is the lesser of the following:
(1) The load limit established by the tire manufacturer, on the tire sidewall.
(2) A load of 620 pounds per lateral inch of tire width, as determined by the manufacturer's rated tire width on the tire sidewall. The steering axle, however, must go by the load limit by the tire manufacturer.

so by his chart, he can not exceed 2843lbs on the rear axle, at least by California law.
 
#39 · (Edited)
620 x 5.5" tread width is 3415 lbs x two tires = 6830 lbs on rear axle.
Our tires are generally wider than this which is the tire manufacturers "margin of safety".

However if the sidewall states a lower weight that is the limit.
 
#40 ·
What is the minimum/maximum single axle weight limit that States must enforce on the Interstate System?
It is 20,000 pounds or a higher grandfathered weight.

May States set weight limits on the Interstate System at less than the Federal maximum weight limits?
No. When Interstate System weight limits were raised to the current levels in 1974 (20,000 pounds single axle, 34,000 pounds tandem axle, 80,000 pounds overall gross weight limits, plus bridge formula limits), States were not required to raise their limits accordingly, although most did. However, six contiguous States in the Mississippi Valley, referred to as the "barrier States," did not and effectively limited the weight for all vehicles moving across them to their own limits. This was changed in 1982 when Congress established Interstate System weight limits as minimums as well as maximums.

Pulled this from the FHWA sites link I posted. There is way more information about commercial towing and what is allowed and expected. Also covers logs, resets, etc etc.
 
#41 ·
I wonder if there is a determination regarding axle weight that is separate from
tire weight? Who knows? The California dmv site I looked at also had the same info that you are posting here, but this excerpt that I quoted was right below that info.
 
#43 ·
I do find it more than a coincidence that my GAWR RR is set exactly to the pound of the Tire Rating. Obviously the mechanic suspension can take more weight but I doubt better tires will change the Rating.

Most of the government sites specifically say better tires and air bags/extra leaf springs don't change the Rating. With the Diesel engine it's the GVWR that is the easiest to exceed.

I am currently towing a 26 foot 5 th wheel with no pull outs weigh in 5500 lbs dry and a 550 lbs pound hitch weight. My truck hardly notices it.

I am thinking about purchasing this trailer.


My current trailer has been across Canada and USA. I don't just go to the local lake, I travel. I have driven Rogers Pass in the winter, Grants pass in the rain at night and the Coquihalla highway in the heat of summer. I worry about loading and braking not so much from a legal stand point but more of safety one. Not all planned vacations work out the way we intended.
 
#42 ·
I have never checked all states rules because it was explained to me that the FHWA rules supersedes all. I have towed and been weighed in all the lower 48 states and DC with no problems however.

All this stuff proves is you can legally tow most any RV, doesn't mean EVERYONE should. Very large trailers take a distinct skill set and awareness to safely transport because of the length, height, and vision challenges. Wind and weather conditions should be noted and planned for, you can't just stop "anywhere". It is very easy to end up on a surface street with trees too low, corners too tight to negotiate, and no room to turn around. My own personal fifth wheel is only a 27' Wildcat so that I could maneuver it onto my Kentucky hunting property. Not trying to insult anyone but in my opinion you should "work your way up" to a large trailer.
 
#44 ·
You will have no problems towing that trailer, legally or otherwise.

With our era trucks the differences between one ton and 3/4 ton are few basically steel wheels only for one ton and more leaf springs. Rearend is geared the same with the same bearings. I have been told and read on here the frame is also the same but honestly never followed up on that. Again I have 521,000 miles doing this with the original engine(never had a valve cover off), original transmission (I did install a stock LML converter $400), original rearend. My truck is set up just like in my sig. These trucks will handle large amounts of weight safely and reliably.
 
  • Like
Reactions: TiredFarmer
#49 ·
Maybe so, but they don't look the same, possibly due to parallax error cuz of the dual wheels.
 
#50 · (Edited)
This is the information I wrote down a couple of weeks ago on the 2500 and 3500. Couldn't find anything specifically on a dually so you're most likely correct about the dually. Whatever the case, no doubt a 3500 dually is going to carry a hell of a lot more weight than a 2500 SWD.





Genuine GM AXLE SHAFT - 2015 GMC Sierra 3500 HD (20920666)
Genuine GM AXLE SHAFT - 2015 GMC Sierra 2500 HD (20920666)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top