Moving up to a Ram 2500.. but have some weight questions..
Hello again,
I'm an engineer and I like equations that balance. But I am up against two differing sets of equations that are NOT matching. I was hoping to get some feedback here...
summary
After renting and borrowing several travel trailers with our 2014 Expedition EL (w/ HD Tow Pkg), we are now in the process of moving up to a RAM HD truck. Currently looking at the 2014+ RAM 2500. We don't want a dually, and we have a family of five. We're looking at a 2500 Crew Cab. The 3500 SRW increases payload but not much more. But it's payload on the 2500 that I'm concerned about. I have read so many posts, and talked to so many people, about pin weights, pin weight ratios, axle ratings, etc, that my head is spinning. Some say ALL my numbers need to be in-spec. Others say axle ratings and gcwr are what matters and tow vehicle gvw's are simply for class categorization of a vehicle.
But -- let's go through a specific example:
truck: 2014 Ram 2500 CTD 4dr 4x4 SRW Long Bed 3.42 (using this fantastic post!)
5th wheel: Highland Ridge LF295FBH (Mfgr Website)
kingpin weight ratios
I hear folks say 20-25% trailer UVW, some say 20-25% trailer GVW. However manufacturers ratings go as low as 15% UVW on their spec sheets! In the RV above, the mfgr shows a 1,351lb hitch weight which is only 15% of UVW's 8,995lb ...
gvwr/payload vs axle ratings
From what I can find, the axle ratings generally seem to add up to more than the gvwr. The vehicle listed above has a gvwr of 10,000lbs but a combined axle rating of 12,500lbs. Payload is calculated by gvwr - curb weight, which equals 2,180lb; but if you calculate payload as axle rating - curb weight, you more than double to a whopping 4,680lbs!
calculation differences
payload vs axle ratings makes a huge difference in kingpin weight ratios, using the examples above. With the two calculation methods described above, there are two possible outcomes. But first some assumptions:
gcwr is totally fine: tv curb weight (7,818) + rv gvwr (10,995) = 18,813.... WAY under the tow vehicle's gcwr of 25,000; Also, rv gvwr (10,995) is also way under tow vehicle's max tow capacity (17,010).
family+in-cab stuffs: 600lb for axle calculations, or 450lb (600-150) for payload calculations (b/c http://www.rambodybuilder.com specifically says the 2014 Ram 2500 payload number includes a 150lb driver)
5th wheel hitch: ~150lb
using payload method: 2,180 - 450 - 150 = 1580lb
using axle rating method: 4,680 - 600 - 150 = 3930lb
Wow! That's a huge difference!
trying to close the loop
Using the payload method, I can only tow the highland 295FBH with between a 14-17% kingpin weight ratio (14% of gvwr, around 17% of uvw). However, if I use the axle rating method, I can easily tow it *fully loaded* (10,995lb) with a 25% kingpin weight ratio (2750lb) and still have another 1,180lb of safety margin!
This is a HUGE difference. And there are plenty more RV's that fit into this scenario with something like a 2014 RAM 2500.
..dane
EDIT: fixed rv link
I'm an engineer and I like equations that balance. But I am up against two differing sets of equations that are NOT matching. I was hoping to get some feedback here...
summary
After renting and borrowing several travel trailers with our 2014 Expedition EL (w/ HD Tow Pkg), we are now in the process of moving up to a RAM HD truck. Currently looking at the 2014+ RAM 2500. We don't want a dually, and we have a family of five. We're looking at a 2500 Crew Cab. The 3500 SRW increases payload but not much more. But it's payload on the 2500 that I'm concerned about. I have read so many posts, and talked to so many people, about pin weights, pin weight ratios, axle ratings, etc, that my head is spinning. Some say ALL my numbers need to be in-spec. Others say axle ratings and gcwr are what matters and tow vehicle gvw's are simply for class categorization of a vehicle.
But -- let's go through a specific example:
truck: 2014 Ram 2500 CTD 4dr 4x4 SRW Long Bed 3.42 (using this fantastic post!)
5th wheel: Highland Ridge LF295FBH (Mfgr Website)
kingpin weight ratios
I hear folks say 20-25% trailer UVW, some say 20-25% trailer GVW. However manufacturers ratings go as low as 15% UVW on their spec sheets! In the RV above, the mfgr shows a 1,351lb hitch weight which is only 15% of UVW's 8,995lb ...
- Question: Is the mfgr being misleading, or is this RV "designed" to be pulled with a 15% kingpin hitch ratio?
gvwr/payload vs axle ratings
From what I can find, the axle ratings generally seem to add up to more than the gvwr. The vehicle listed above has a gvwr of 10,000lbs but a combined axle rating of 12,500lbs. Payload is calculated by gvwr - curb weight, which equals 2,180lb; but if you calculate payload as axle rating - curb weight, you more than double to a whopping 4,680lbs!
- Question: Why do the combined axle ratings so often *exceed* the tow vehicle's gvw?
calculation differences
payload vs axle ratings makes a huge difference in kingpin weight ratios, using the examples above. With the two calculation methods described above, there are two possible outcomes. But first some assumptions:
gcwr is totally fine: tv curb weight (7,818) + rv gvwr (10,995) = 18,813.... WAY under the tow vehicle's gcwr of 25,000; Also, rv gvwr (10,995) is also way under tow vehicle's max tow capacity (17,010).
family+in-cab stuffs: 600lb for axle calculations, or 450lb (600-150) for payload calculations (b/c http://www.rambodybuilder.com specifically says the 2014 Ram 2500 payload number includes a 150lb driver)
5th wheel hitch: ~150lb
using payload method: 2,180 - 450 - 150 = 1580lb
using axle rating method: 4,680 - 600 - 150 = 3930lb
Wow! That's a huge difference!
trying to close the loop
Using the payload method, I can only tow the highland 295FBH with between a 14-17% kingpin weight ratio (14% of gvwr, around 17% of uvw). However, if I use the axle rating method, I can easily tow it *fully loaded* (10,995lb) with a 25% kingpin weight ratio (2750lb) and still have another 1,180lb of safety margin!
This is a HUGE difference. And there are plenty more RV's that fit into this scenario with something like a 2014 RAM 2500.
- Question: Before I purchase the truck, how do I reconcile these two vastly different outcomes?
..dane
EDIT: fixed rv link
