determining pin weight

RCMAN46 wrote:

Cajun Bill wrote:
Okay sports fan, OP here. Got 'er done this morning.

Truck only:

steer axle 4400
drive axle 2920

total weight 7320

truck and fiver:

steer axle 4220
drive axle 5460
trailer axle 9720

total weight 19400

Note: people weight--driver 275 lbs. (no derog comments please)
gray and black tanks empty, fresh water--approx 15 gallons
fuel tanks 1/2 full (13 gal. diesel)

Other info---according to my truck manual, GCWR is 22,000 lb, so my 19400 is well within limits. Max trailer weight according to manual is 14,200 lbs and at 12,080, that gives me over 2k more carrying capacity and since the trailer has almost everything I normally carry except groceries and clothes. The most passenger weight I might have is an additional 460 lbs.

Now, what is my pin weight? 5460-2920= 2,540 lbs.???? And if that is close, am I within limits?

Your true pin weight is 2360.

You have a truck on the scales that weighs 7320 (4400+2920)
Now imagine the truck is still on the scales and you lower the trailer pin on to the truck. Now the truck weighs 9680 (4220+5460) You had to add 2360 to get the truck to weigh the 9680.

Believe what you want but your actual pin weight is 2360.

Your pin percentage is pin/trailer. 2360/12080=.195 or 19.5%. A little low for a 5th wheel to handle well and not chuck.

Your hitch must be a couple inches behind the centerline of the rear axle or there was no driver in the truck during the second weighing.



This is why it is important to know actual pin weight.

Another way to look at this. Truck and trailer weighs 19400 and the truck weighs 7320. That means the trailer weighs 12080.
The trailer axle weight was 9720. Pin =total trailer-trailer axle.
12080-9720=2360.

But to be accurate there can be no loading changes between weighing's. The same people, fuel or anything else has to be in the truck both times.

OP here. The hitch is located just slightly ahead of rear axle on truck. Everything essentially stayed the same, (maybe burned a gallon of diesel going get the fiver) and I was on the scale in both instances (on the steering axle part of the scale in both instances).

So lets assume the pin weight is 2360, not 2540 as I calculated. 180 lbs. is no big deal IMHO. If it's 2360, am I within limits? And no, I don't know my rear axle recommended limit cuz I don't see it in the book.

The whole purpose of this exercise was to see if possibly, maybe, sorta kinda, could my pin weight be causing the belts on my rear truck tires to slip? and yes, I always pull the fiver with max pressure (80 psi) in the rear tires.