Quote:
Originally Posted by T and C
Mtnguy,
I puzzled over your post for a while. Then I went to a Ford F150 site and read that many owners have replaced their class III hitches with class IV hitches at a cost of about $300.
Then I went to bed.
When I awakened this morning it was obvious to me that my subconcious mind had worked on the problem while I slept. The answer just surfaced in my thoughts as I awakened.
Look at those numbers again. We have been thinking that the 500/5000 limit had to do with the shear strength of the bolts that attach the hitch to the truck. BUT...look at that 990/9900 figure. If you load the hitch at 501 pounds it will fall off?  But if you put a WDH on it will bear 990 pounds with no problem???
The answer is that both ideas are wrong. What Ford is regulating here, (to avoid liability), is SWAY. 500 and 990 are both exactly 10% of the weight limit they recommend. As we all know, the standard figure for the RV industry at large is that tongue weight should be limited to 10-15% of trailer weight.
But...TM's do not fit the average. Their axle configuration and low wind resistance both serve to limit sway beyond the normal limits. 
So, I am not going to sweat the 500# limit too much.
Now if I throw an extra can of beans in the trailer and then the hitch falls off, I'm wrong.
Tom |
Tom,
A hitch receiver supports more tongue weight with a WDH than without (as does the tow vehicle). Sway has a lot to do with on the road stability, but probably not much to do with the tongue weight carrying capacity of a hitch receiver.
Quote:
Originally Posted by T and C
Bill,
We were talking about the air bags preventing so much weight working the springs up and down. Matt feels that this harms their resiliance. The air bags support much of the weight the springs would have to bear. I am aware that they do not reduce axle weight.
On my older truck I frequently carried an overhead camper that weighed 1450 pounds. It put my weight right at gvwr with a tank of gas two passengers, and some stuff in the camper. w/o the air bags it would have sagged and rocked back and forth on the road. Not safe at all. So...I am used to having the bags in place.
Tom
|
Harm the springs? Bullfeathers. "Extra weight..."? Air bags make the suspension stiffer, but they don't change your rear axle weight or the weight rating your manufacturer provided. A stiffer suspension actually might give you additional rear axle weight carrying capacity. Or not, if there is a limiting factor that's something other than springs (like tires or the axles themselves). It's probably OK to have the airbags, given that they were made by someone who thought about these things. But you're potentially exceeding your rated rear axle capacity and you would be violating your manufacturer's warranty if you did that.
Ratings are guidelines, and I share your lack of concern about a can of beans. But a weight distributing hitch keeps the trailer tongue weight from unloading the front wheels, which air bags can't do. So, you're still reducing the weight on your front wheels where most of your braking and all of your steering happens.
Regardless, you've taken quite a leap from that lofty "erring on the side of caution" perch you were posting from earlier in this thread.