'18 F-150 Car Trailer w/o WDH
05-18-2018, 07:45 PM
#21
Senior Member
A WDH does NOT remove weight from a hitch receiver and hitch. It only affects how the truck is carrying the weight ....most importantly...the front end and what it shifts to the trailer.. It doesn't change the weight on the tongue, just how the setup carries the weight. Confusing eh? One thing to keep in mind, the WDH only works if it has tongue weight to work with. Therefore, the tongue weight remains almost the same.
This comes from this site: http://www.rv.net/forum/index.cfm/fu...d/14265335.cfm
I can load my equipment trailer with tractor on it, and the front end of the truck only goes up 3/8 of an inch. That is with just over 700 lbs on the tongue. I am within safe limits of unloading the front end of my truck. Still can't figure out why I have a 4050lb rated front end lol. I am well beyond my rear GAWR and/or my payload way before I get beyond the capabilities of my Class IV hitch.
This comes from this site: http://www.rv.net/forum/index.cfm/fu...d/14265335.cfm
A weight distribution system enables a tow vehicle to more effectively handle the tongue weight of a trailer by removing some of the load from the tow vehicle's rear axle and distributing it to the tow vehicle's front axle and the trailer's axle(s). Note - When the WD system is engaged the actual tongue weight does not change. Recommended tongue weight is from 10% to 15%.
I can load my equipment trailer with tractor on it, and the front end of the truck only goes up 3/8 of an inch. That is with just over 700 lbs on the tongue. I am within safe limits of unloading the front end of my truck. Still can't figure out why I have a 4050lb rated front end lol. I am well beyond my rear GAWR and/or my payload way before I get beyond the capabilities of my Class IV hitch.
Last edited by Simnut; 05-18-2018 at 07:50 PM.
05-18-2018, 07:48 PM
#22
I'm not sure why you went to a comparison of the 145" WB vs a 157" WB? This comparison seems somewhat irrelevant to the discussion topic given that the 500 pound tongue weight applies down to the lightest 122"WB RCSB.
If you compare the extremes, the lightest duty 122 WB RCSB to the heaviest duty 164 WB HDPP, the additive affect of more front end weight and longer wheel base is substantial. And the 157" WB SCREWs are heavier in front than the 164 WB so they have nearly the same results. Either will be less affected by 800 pounds of tongue weight WC, than the lightest duty 122 WB RCSB is with 500 pounds tongue weight WC on a percent basis. And in the case of the 157" WB SCREW, it still has ~400 pounds more weight on the front end with 800 pounds WC tongue weight than the lightest RCSB has empty with no trailer. This is intuitive when you consider the front end of the longest, heaviest F150 variants start out ~700 pounds heavier (compared to lightest RCSB) and that weight is ~3ft further from the rear axle.
Last edited by Gladehound; 05-18-2018 at 08:00 PM.
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Simnut (05-18-2018)
05-18-2018, 08:14 PM
#23
There is another important point that has not been discussed. The wheel base effect really should be squared (which I didn't do anywhere above) because a longer wheel base reduces the amount of weight removed from the front, AND it reduces the amount of force that the front tires have to exert or resist in order to turn or stabilize the rear respectively. So everything to this point has been an underestimation of how much more WC tongue weight the longer, heavier variants of the F150 can handle with equal stability to the lightest RCSB.
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Simnut (05-18-2018)
05-18-2018, 08:19 PM
#24
Senior Member
There is another important point that has not been discussed. The wheel base effect really should be squared (which I didn't do anywhere above) because a longer wheel base reduces the amount of weight removed from the front, AND it reduces the amount of force that the front tires have to exert or resist in order to turn or stabilize the rear respectively. So everything to this point has been an underestimation of how much more WC tongue weight the longer, heavier variants of the F150 can handle with equal stability to the lightest RCSB.
05-19-2018, 07:51 AM
#25
I used those two trucks just for comparison just to show the amount of weight transferred based on WB. The difference between 122 and 163 is only about 50 lbs but yes comparing that as a % of FAW it becomes more relevant. A shorter WB becomes a factor because it moves the TV CG closer the hitch point. It takes less force to start lateral acceleration the closer the TV CG gets to the hitch point and rear axle(pivot point). You see the same thing on the trailer side, the closer the CG gets to the rear axle(pivot point) the more likely it is to sway.
Its actually nice to see someone acknowledge the importance of TV mass to towing stability as you show the importance of 400lbs FAW between f150 models. The TV with a higher unladen mass will help dampen sway faster than a lighter one especially when the extra mass is located over the front axles. The extra mass up front helps keep the CG forward when hitch load is added. Now imagine how much stability is gained when the front axle weight is 1000lbs + higher then a SCREW f150 as is the f250? A PSD f250 will be 1600lbs + . This why the f250 is a better choice regardless of a payload sticker. Payload ratings don’t really dictate towing stability contrary to what gets parroted on forums around the web. TV WB and mass are just two important characteristics of many that can effect towing stability. Take advantage of these two characteristics when you can.
As Simunt says a WD doesn’t move the hitch weight and this is true. Adding hitch mass shifts the vehicle CG rearward, applying WD does not shift the CG back forward where it once was before HW was added. This is the basis for reducing FALR% with a WD hitch.
Its actually nice to see someone acknowledge the importance of TV mass to towing stability as you show the importance of 400lbs FAW between f150 models. The TV with a higher unladen mass will help dampen sway faster than a lighter one especially when the extra mass is located over the front axles. The extra mass up front helps keep the CG forward when hitch load is added. Now imagine how much stability is gained when the front axle weight is 1000lbs + higher then a SCREW f150 as is the f250? A PSD f250 will be 1600lbs + . This why the f250 is a better choice regardless of a payload sticker. Payload ratings don’t really dictate towing stability contrary to what gets parroted on forums around the web. TV WB and mass are just two important characteristics of many that can effect towing stability. Take advantage of these two characteristics when you can.
As Simunt says a WD doesn’t move the hitch weight and this is true. Adding hitch mass shifts the vehicle CG rearward, applying WD does not shift the CG back forward where it once was before HW was added. This is the basis for reducing FALR% with a WD hitch.
Last edited by 8100hd; 05-19-2018 at 08:13 AM.
05-19-2018, 09:09 AM
#26
Senior Member
I had a 2004 Ram 2500 and it also had the 500/5000 numbers on the hitch. It was a class IV hitch. I had a 2011 Chevy 2500 that didn’t have the restriction but it had a class V hitch. You could see the hitch was much stronger. My guess is a 3/4 ton truck is built to take the heavier hitch weight where an F150 isn’t. So my opinion is the hitch is what requires the 500/5000 limits without a WDH but the truck limits it also.
05-19-2018, 09:24 AM
#27
700 pounds is the difference in the front ends of the lightest RCSB and many heavier variants of the F150. I don't know the max front end weight but wouldn't be surprised if a fully optioned out SCREW 6.5 bed would be 800 or 900 pounds heavier on the front than the lightest RCSB. 700 pounds is for my truck.
Mass is one of many factors. Where the mass is also important as noted above. Rigidity of the truck right down to the tire contact patch is also important as is traction. Traction seems to be an oft overlooked factor. In an extreme hypothetical example, with a completely rigid system and perfect traction, mass falls out of the equation. Back to the real word, a lighter very rigid truck with a higher coefficient of friction at the contact patch could overcome some disadvantage in mass. Needless to say, tire quality is important.
Mass is one of many factors. Where the mass is also important as noted above. Rigidity of the truck right down to the tire contact patch is also important as is traction. Traction seems to be an oft overlooked factor. In an extreme hypothetical example, with a completely rigid system and perfect traction, mass falls out of the equation. Back to the real word, a lighter very rigid truck with a higher coefficient of friction at the contact patch could overcome some disadvantage in mass. Needless to say, tire quality is important.
05-19-2018, 04:14 PM
#28
An F150 has a lot of advantages over an F250 for things other than towing and that's why people who do mixed duty buy them. I don't see ever bothering with a diesel F250 again. If I go bigger than the F150, I'll skip right over the F250 to get some real payload. Actually was thinking F550 with SRW conversion 40" tires, flat bed with custom storage boxes and a slide in camper.
05-19-2018, 06:11 PM
#29
A tires grip and traction increases with load though not proportional. You can’t increase traction by making something more rigid, you can’t substitute strength for mass. I don’t know of any currently produced trucks that are not rigid enough to handle a “reasonable” load or has poor lateral stability. As far as I’m concerned most manufacturers rate beyond reasonable pretty much across all classes of trucks not just 1/2 tons.
Last edited by 8100hd; 05-19-2018 at 06:32 PM.
05-19-2018, 06:46 PM
#30
I had a 2004 Ram 2500 and it also had the 500/5000 numbers on the hitch. It was a class IV hitch. I had a 2011 Chevy 2500 that didn’t have the restriction but it had a class V hitch. You could see the hitch was much stronger. My guess is a 3/4 ton truck is built to take the heavier hitch weight where an F150 isn’t. So my opinion is the hitch is what requires the 500/5000 limits without a WDH but the truck limits it also.