Took a trip to the CAT scales

[slowmover]

Originally Posted by nilesrob

Totally get the headache thing. Here are my results. Any thoughts appreciated!

The trailer tows great, although the tail end of my TV seems to hang a little low when hooked up...

Good job on acquiring scale tickets.

The FA is the crucial first step in establishing a proper baseline.

FA, solo: 5,040-lbs

This is what we also want with the trailer hitched and WD activated.

Trailer hitched, no WD: 4,560-lbs (480-lbs removed)

Trailer hitched, WD active: 4,760-lbs (280-lbs short of best)

Further adjustment needed, IMO.

FORD, IIRC, recommends a 50% "return" when WD activated which you about meet. I'd rather go to 100% (or as close as hitch will do it). Check their guidelines for your model truck as that should be the background to your decisions/adjustments (as with GVWR, GAWR, etc, etc).

More:

RA increased by 1,480-lbs w/o WD activated.

With WD activated, 200-lbs "went" to the FA and only 40-lbs to TT axles.

Just not enough leverage by the WDH, yet.


(The Ron Gratz Chart)

Weighing #1 -- TT attached and Weight Distribution Activated

Let Front Axle Load be "FA1" 4760

Let Rear Axle Load be "RA1" 5160

Let TT Axles Load be "TT1" 5660

Then, while in same position on scales, take
Weighing #2 -- TT attached and Weight Distribution Not Activated

Let Front Axle Load be "FA2" 4560

Let Rear Axle Load be "RA2" 5400

Let TT Axles Load be "TT2" 5620

Then, drive off scales and drop TT. Return to scales and take
Weighing #3 -- TV only -- TT Not Attached

Let Front Axle Load be "FA3" 5040

Let Rear Axle Load be "RA3" 3920

From the above values, you can calculate:

TV weight = FA3 + RA3 8960

Gross Combined Weight = (FA1 + RA1 + TT1)
- should also be equal to (FA2 + RA2 + TT2) if scale weights are correct

15,580

15,580

TT Weight = Gross Combined Weight - TV Weight

15,580 - 8960 = 6,620


Tongue Weight = (FA2 + RA2) - (FA3 + RA3)

9960 - 8960 = 1,000

TW = 15%

Load Transferred to TT Axles
when WD System in Activated = TT1 - TT2

40-lbs

With a 1k TW we'd more likely see around 240-lbs shifted to the trailer axles once the FA weight is "restored" to it's solo value.

While "level" is really only important for the trailer (independent suspension; we want both axles loaded the same as they would not be if the trailer were nose high or low; braking, etc), and slight tail down no big deal for the TV, a better set of adjustments to your hitch will probably pick up the tail a bit.

But there is no doubt that the steering and braking will be improved by further tweaks to the WDH. The more the load on the TT tires, the better will be the combined braking of the rig. Not to mention best anti-sway.

Once done, with new scale tickets, one can also look at TV tire pressures for best performance within vehicle manufacturer guidelines, and check that TT tires still have a 12-15% load reserve against the WD activated scale value divided by four (TT tires are always to be at maximum sidewall pressure, cold).

Perfect is hard to achieve for some rigs . . but the closer one comes the better will the combination rig perform. And this eliminates a lot of guesswork if in the future "something" doesn't seem right anymore (ask BoondockDad about whether it was his worn hitch or his new tires causing a hoochie-koochie dance with his rig on a great thread from a little while back. Eliminating problems because one has solid numbers is a real boon).

Unless you sell either, or greatly change the loading of one or both vehicles, this baseline is good for many years to come. Just check it every so often the same way. A stack of scale tickets -- updated & clipped in your logbook -- is your very good friend. Confidence in a rig is in real time from real numbers . . but confidence itself cannot be measured accurately when it comes to the test. Give it some more work. It'll be the best beer you ever earned (you'll say to yourself someday).

.

[nilesrob]

Rednax, awesome advice. I will make some adjustment to the WD, and next time by a scale will give it a whirl. Thx for the thoughts and recommendations.

[KYAirstream]

Originally Posted by Inland RV Center, In

To be safe the maximum difference of weights between the front and rear axle, should be no more than 10 percent.

Andy

I was digging through threads about cat scale weights, and was hoping some clarification could be provided about this 10% rule? Does it mean that there should be no more than a 10% weight difference between the weights of front and rear TV axles? That is, when hitched with weight distribution, if the front TV axle weighs in at 3000lbs, then the rear TV axle shouldn't weigh more than 3300lbs?

Or is it that the unhitched front and rear TV weights shouldn't differ by more than 10% from the hitched front and rear TV weights? That is, if unhitched the front axle TV weight is 3000 lbs, then hitched it shouldn't be less than 2700 lbs nor more than 3300lbs? And likewise for the rear TV axle...

[bwpaint]

following --good info on thread

[slowmover]

The spread of WD weight between FF and RR axle on the tow vehicle is ideally no more than ten percent, with the bias toward the RR.

This in achieving a spread of the TW equally across the three axle sets.

[KYAirstream]

Just so there is no confusion, would you mind providing an example using numbers?

[KYAirstream]

Also, I assume FF refers to front of TV and RR to rear?

[ghaynes755]

Here's the weight calcs in an excel file. Formulas based on the Ron Gratz methods.

Cat Calc Sierra 2500 5-3-14.xlsx

[KYAirstream]

Thanks for the spreadsheet. I look forward to plugging in some numbers.