Tongue Weight Rating

Ron Gratz wrote:

LarryJM wrote:
I look at this a a fairly straight comparison with the tongue wt. being the weight of the bikes and the WDH system and bars being the same as the bike rack.

I don't see any comparison at all. A bike rack is not a weigh distribution hitch. It does not have the ability to remove load from a receiver the way a WDH does. This thread is about tongue weight rating when using a WDH.

I have also read that once you get things hooked up any wt. you add to the TV behind the axle should be considered as "additional" tongue wt.

I've read a lot of stuff on the internet which I consider to be nonsense. If weight behind the rear axle is considered to be "tongue weight", does that mean it also must be subtracted from the receiver's tongue weight rating? I think not.

I guess the way I look at it is that the receiver is designed to support a certain dead wt in direct load bearing or WDH bearing which is the actual load on the receiver.---

The actual vertical load on the receiver is weight of WDH plus tongue weight minus load transferred to TT's axles. In most cases the load transferred to the TT is greater than the weight of the WDH. That means the actual vertical load on the receiver would be less than the tongue weight.

---You could hook up your WDH system and not engage the WDH portion and I guess the question is do you ignore the 100lbs approx of the WDH and bars against the receiver weight carrying capacity and if so why or where does it go.

If you use a WDH as a "weight carrying" hitch, the question is -- how much weight of hitch already is included in the "weight carrying" tongue weight rating?
I'm guessing that the people who establish receiver ratings are aware that, when used in WC mode or WD mode, there will be a WC or WD hitch installed in the receiver. And, I'm guessing that the weight of a typical WC or WD hitch already is included in the receiver's rating.

Ron

Ron, I read through this post (http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/14265335.cfm) and I can’t say I understand the physics or where the formulas come from, but I get the gist of how the WD hitch distribute weight between the TT and TV axles. What I didn’t realize (fully) is, when installed, WD hitches do not change tongue weight. This was mentioned a couple times throughout this thread and it took a bit for that to sink in. I’m still not sure I understand why that is, but I can accept it.

The reason I didn’t catch on to that at first (and this goes to the OP’s original question) is on my old truck (1/2 ton Silverado) the sticker on the receiver read something like 600 lb. TW and 1,200 TW with a WD hitch. (The class V hitch on my new TV doesn’t say that—it just says 1,500 lb. TW) So somehow (through the magic of physics) adding a WD hitch increases the amount of tongue weight you can apply to the receiver.

So my question is, if a given hitch is rated for a tongue weight of (for instance) 600 lbs. and WD hitches do not change tongue weight, how does adding a WD hitch increase the allowable TW to (for instance) 1,200 lbs.? I’m sure there’s something I’m not seeing here.