I'll offer another opinion.
According to Reese, (and they have said this for at least the last 11 years I know of) Reese states that weight in the truck behind the rear axle is to be applied to the sizing of the WD bars.
This is a 4 meg Reese WD catalog file if you hit on it.
www.reeseprod.com/support/catalogs/Cequent-2015-06-Weight-Distribution.pdfSee the last page, page D-20 on the PDF.
Reese wrote:
The hitch weight formula for determining the load
which the hitch must carry:
HITCH WEIGHT* = TONGUE WEIGHT +
VEHICLE CARGO LOAD BEHIND REAR AXLE
OK, so that is what Reese has said for some time now. But, they do not describe to you how that actually works into the sizing of the WD bars. They leave it wide open for you to interpolate or just buy larger bars to cover any anticipated truck bed loads.
Now to the setup.
If you check your
unhitched truck front fender heights or axle weights
with the truck bed loaded and you hitch up and adjust the WD hitch to return the front end to unhitch height/weight, then the load on the WD bars is only from you adjusting the hitch.
OTOH If after you had adjusted the hitch as described above;
And you add extra weight to the truck bed behind the truck rear axle which is a large enough weight and or far enough behind the axle to lower the back of the truck, this can change the hitch head angle relationship to where it was originally adjusted to and add a level of tension to the WD bars. How much tension rise in the WD bar depends on how much the hitch head angle changed.
That is the only way I can figure (right now at least) why they feel you need to upsize the WD bars. If there are other ways, please point them out.
John
