Help Deciphering CAT Scale Weights

[MHay]

Hi all,

New to the forum, and to RVing. I want to make sure my WDH is adjusted properly. I took my rig and travel trailer (TT) to the scales this past weekend and did three passes: first was hooked with WDH bars in place, second with WDH bars released, and third was rig and trailer separated. The weights are below. What I'm trying to determine is whether or not I can get more weight off the rear axle and distributed to the front and TT axles. Weights displayed are in pounds.

1st Pass (Connected with WDH bars):
Steer Axle: 3,020
Drive Axle: 4,560
Trailer Axle: 6,560

2nd Pass (Connected without WDH bars):
Steer Axle: 2,740
Drive Axle: 4,960
Trailer Axle: 6,460

3rd Pass (Disconnected trailer from rig):
Steer Axle: 3,200
Drive Axle: 3,560
Trailer Axle: 7,400

From these measurements, I calculate the tongue weight to be 940 pounds (7,700-6,760). Comparing pass 1 with pass 2, using the current setup the WDH bars seem to add 280 pounds to the steer axle, take 400 pounds off the drive axle, and add 100 pounds to the trailer axle. Should I be aiming for more weight on the steer axle (it's 180 pounds lighter than normal drive weight), and less off the drive axle (1,000 pounds more than the normal driving weight). And with only 100 pounds being transferred to the trailer axle, it seems like there's more that could be moved there.

[MHay]

BarneyS wrote:


I would aim for getting the brackets at the right level so the bars rest evenly across the surface. Than I would tilt the hitch head rearward until I got the weight transfer that I wanted.

This all assumes that you trailers A frame can take the stress of the additional pressure the WD bars will put on it via the brackets. You have very strong, square, non tapered WD bars that are not too flexible. It is not unheard of for A frames to bend or break from excess WD pressure, especially when going through a dip like you would find at a gas station or other driveway or even some RR crossings. If your frame is a 6 inch frame or larger it should be ok.
Barney

I finally took the time to make some adjustments. I added the larger spacer to tilt the head back some more. I also dropped the frame brackets by one notch to relieve some tension and to level out the bars. I tried it out at that setting and it “felt” like there was too much tension. I could see the bars bending when tensioned and there was lots of additional popping noises when driving. I then lowered the brackets one more notch and that seemed to be a good balance.

I stopped at the scales yesterday on our way home from a trip and the numbers confirm that the weight has been spread to the TV front axle and TT axles. Note: trailer weight has increased by 420 pounds due to water and other cargo. Despite the extra weight the adjustments have still taken more weight off the rear axle and moved it to the front axle.

TV Front Axle: 3,120 (was 3,020)
TV Rear Axle: 4,480 (was 4,560)
TT Axles: 6,960 (was 6,560)
New Gross Weight: 14,560 (was 14,140)

I’m still 100 pounds above the rear GAWR for my truck, so I’m considering adding the last washer to tilt the head back to its max, leaving the frame brackets where they are, to see if I can squeeze anything else out of it.

[BarneyS]

MHay wrote:
Snip...
I'm using a Curt TruTrack hitch rated at 15,000 GTW and 1,500 TW. Currently I have the brackets on the trailer as high as they'll go. I have not tried tilting the hitch head yet, which I believe would apply more tension. As it is now, the trunion bars seem to be exerting lots of force on the angle brackets, to the point where they are wearing through the black paint on the front of the brackets and starting to mar them. Should I try tilting the hitch head back in an attempt to get more weight off the rear axle, or does it seem like I'm fairly maxed out already? Here's a link to the instructions: Curt TruTrack Hitch.

We're headed on a trip tomorrow, so I'll try to get a picture of the current setup once I'm hooked up.

You mention that the paint is wearing on the front of the L shaped angle brackets. You also state that the brackets are as high as they can be on the frame. That tells me that you should lower your brackets on the frame and then also tilt your hitch head rearwards. The spring bars should rest evenly on those brackets - not contact them just on the front edge or rear edge like they are doing now.

I would aim for getting the brackets at the right level so the bars rest evenly across the surface. Than I would tilt the hitch head rearward until I got the weight transfer that I wanted.

This all assumes that you trailers A frame can take the stress of the additional pressure the WD bars will put on it via the brackets. You have very strong, square, non tapered WD bars that are not too flexible. It is not unheard of for A frames to bend or break from excess WD pressure, especially when going through a dip like you would find at a gas station or other driveway or even some RR crossings. If your frame is a 6 inch frame or larger it should be ok.
Barney

[BenK]

Tilting the WD Hitch head only moves the bar farther away from the tongue mounted brackets...but...the bar spring rating does NOT change. Just bending it more and at some point, the bar may deform enough to never again have the same rating...less spring bar rating

Why asked what the bars are rated for. If you bars has enough spring rating, then tilting the head will be fine

Your WD Hitch uses the friction between the bar bottom side against the bracket and the wearing of the paint part of how it works

It will make metal on metal noise and too often read here that someone advises to grease/oil that union

Since friction is the main anti-sway component (not as much friction as a friction bar would provide) and adding lubrication an oxymoron...though many do so. I don’t recommend it...even knowing that several OEMs instruct to do so if the noise annoying

Your amount of ‘over’ weight on the rear axle isn’t going to have the rear axle fail instantly...just wear a bit more than if below the rating....butt....that will not have any head room for that occasional added weight

Edit...just remembered that some say the newer versions of this type of WD Hitch now has friction material on the bracket that the bar rides on. Now that is the same as traditional friction bars and should remove the metal on metal noise, but think it will still have some noise (haven’t seen one yet)

Maybe your OEM has an upgrade kit to add a friction pad on each side

[Grit_dog]

Good, you're on your trip and not pining over this. Still didn't answer the question of how it "looks" and how it "pulls".
Too much of the time, folks get wound up in splitting hairs on the numbers and, well, honestly that seems to only be a "thing" in the RV world.
If it was that critical, the other millions of light duty trucks pulling...whatever...around daily would need greater scrutiny.

[APT]

Good analysis so far. I agree that more WD force to take more weight off the rear axle should get you really close to the rear axle rating.

[MHay]

Thanks for all the great responses so far!

The GVWR for the Expedition is 7,720 based on the sticker on the door jamb. So based on these weights, I have a little room to spare (pass 1 with the WDH was 7,580 for vehicle weight).

The real issue is the GAWR for the rear axle. The rating is 4,380, but I'm sitting at 4,560. I'm using a Curt TruTrack hitch rated at 15,000 GTW and 1,500 TW. Currently I have the brackets on the trailer as high as they'll go. I have not tried tilting the hitch head yet, which I believe would apply more tension. As it is now, the trunion bars seem to be exerting lots of force on the angle brackets, to the point where they are wearing through the black paint on the front of the brackets and starting to mar them. Should I try tilting the hitch head back in an attempt to get more weight off the rear axle, or does it seem like I'm fairly maxed out already? Here's a link to the instructions: Curt TruTrack Hitch.

We're headed on a trip tomorrow, so I'll try to get a picture of the current setup once I'm hooked up.

[BenK]

Some IMHO comments...and CONGRATULATIONS on actually going out and weigh it. Note that every trip has a potential of different loading, so these numbers should be your base line. Another person & their ‘stuff’, find something along the trip and buy it for the trip home...things have a remarkable tendency to add and add...

What are your WD bars rated for ?

Agree with Barney, try to WD some weight off your TV’s rear axle and over to the TV’s front axle. Note that by doing that, you will also WD a bit more weight back onto the trailer tongue...that is how WD systems work. This will get your TV’s rear weight into a better place in regards to the RGAWR. This is why you need to know where you are in reference to the WD Hitch system bars ratings....do you have enough head room or are you already at their max rating?

The finally orientation of the whole setup, after all of the dials/knobs have been adjusted, is to have enough weight is WD’d to the TV’s front axle as per the manual (some require weight returned to some +/- of stock, others +/- height of stock...stock = before hooking up) and the trailer tongue level at it’s highest pointing and prefer pointing slightly down...they follow better that way

Forget the MTW (Max Tow Weight) listed for a TV. More marketing than anything and that they ‘wiggle’ the setup to get the highest trailer weight for their marketing brochures. The GCWR is better and since you have weighed the whole setup, take the sum of the TV’s axle weights and subtract it from the GCWR (note that GCWR is fairly new to the towing world and is subject to much discussion...many say it is only a performance thing...okay, hows about the ability to manhandle the setup during an emergency situation...of which all ratings has been designed for...among many other things)

Bottom line = I’d tow that with some adjustments and know it is at the limits. Therefore drive accordingly and enjoy the ride...

[Mickeyfan0805]

valhalla360 wrote:

What the GVWR on your truck? I did a quick check online and it looks like 7300lb but you are at 7580lb already but you might have a different model from what I found.

This is the piece of this conversation that I think is getting overlooked in all of this. What is your GVWR, and were you fully loaded, with both people and gear, when you got these numbers? You are not only over RAWR, but likely over your GVWR. If you weren't fully loaded, it means things only get worse from there. If this is a full load, WDH adjustment might help, but that depends on how much you are already dialed in - and you still may be be over weight. If you still have additional passengers or gear to load on top of the weights you are sharing, that just exacerbates the problem.

[valhalla360]

RobWNY wrote:
I'm confused how you lost 20 pounds completely using WDH bars (14,140 compared to 14,160 for the other two weight rating passes).

The specs for scales provide an error tolerance. 20lb is nothing on a truck (and yes, they typically error on the conservative side as truckers get upset if they get an over weight ticket). So with slightly different placement of the vehicle, a little fuel used or other minor changes, it may come up slightly different but still well within spec for the scale.

In the non-WDH, loading the rear axle picks up more weight because some of the front axle weight is moving back to the rear axle (think of the rear axle as the center of a teeter tautter. That also moves more of the trailer weight to the hitch for similar reasons (harder to explain as force distribution is a little more complicated as the WDH is applying a moment arm in the opposite direction around the hitch). This is perfectly normal. I don't have the stationary scale specs but I just checked and for weigh-in-motion systems I work with, the top spec allows 6%+- for GVW. Stationary has closer tolerances but still you aren't going to get it down to the nearest ounce.

Looks like you are about 180lb over on the rear axle. I don't think you can reasonably just crank down harder on the torsion bars to make that up.

I'm coming up with 840lb hitch weight (7400-6560 = 840) and 11% (840/7400). So I would be hesitant to shift weight to the back of the trailer to reduce hitch weight or you could create a sway issue.

Do you have cargo in the rear of the truck that could be moved to the trailer (without exceeding the trailer GVWR). Cargo in the rear of the truck is almost 100% going on the rear axle.

You can check details on the individual rear suspension parts and see what is creating the limitation on the RAWR. The Expedition is likely different but the F250 and F350 (SRW) were for many years identical except for the spring pack, so if you upgraded the springs, you effectively got a F350 (not in legal terms but in practical terms).

What the GVWR on your truck? I did a quick check online and it looks like 7300lb but you are at 7580lb already but you might have a different model from what I found.

[BarneyS]

MHay wrote:
As I think about the numbers some more, things don't add up to me. When using the weights in my original post to calculate tongue weight, I get 940 lbs. However, looking at the drive axle weight on Pass 2 (connected to trailer, no WDH bars), the change in axle weight is 1,400 lbs. from the unloaded weight (Pass 3). If tongue weight is 940, how is the axle weight increasing by 1,400 lbs. when hitched to the trailer without WDH bars? I might need a physics refresher to set me straight.

That increase is because the weight is being removed from the front axle when you put the trailer tongue on the ball. You get the weight of the tongue PLUS the weight from the front axle that was teeter-totter removed. Thus the scale shows the tongue weight plus the removed front axle weight. It is the goal of the weight distributing hitch to place all or most of that weight back on the front axle. In other words, your truck front axle should weigh the same AFTER hooking up the WD bars as it did solo BEFORE you hooked up the trailer.

In your particular case, I would try to adjust the hitch or take up some more on the WD spring bars to transfer some more weight forward.
Barney

[MHay]

JIMNLIN wrote:

I also checked some weights I got at my local garbage transfer station and they were also in 20 lb multiples.

Thus a difference of 20 lbs on separate weights can be expected.

OP...maybe I read it wrong about being over a RAWR I would take some weight off the trucks rear axle. A RAWR is the lessor of a wheel/tire/rear spring pack or the axle itself. Most trucks today weak link can be the OEM wheels or rear spring pack.

No, you read that correctly. I'm over by 180 lbs. which is why I was trying to figure out if I can move more off of the rear axle with the WDH, or just try adjusting the cargo in the trailer. 😞

[Mike134]

RobWNY wrote:
I'm confused how you lost 20 pounds completely using WDH bars (14,140 compared to 14,160 for the other two weight rating passes).

The scale can be off as much as 20lbs high or low and still be "certified" So it's possible to have a 40lb difference if the scale settles high one pass and low the second pass.

[JIMNLIN]

I also checked some weights I got at my local garbage transfer station and they were also in 20 lb multiples.

Thus a difference of 20 lbs on separate weights can be expected.

'zactly.
Just 20 lbs loss or gain is excellent scale numbers.
A first weigh may say 3005 lbs but the scale rounds off to the next highest at 3020 lbs.
The second weigh may say a 2996 lb but rounds off to 2980 lbs for a 40 lb difference.
Wind speed....failure to release the service brakes...fuel/water/liquid slosh in containers/how much fuel was used between re weighs.... can all contribute to different scale weights.

OP...maybe I read it wrong about being over a RAWR I would take some weight off the trucks rear axle. A RAWR is the lessor of a wheel/tire/rear spring pack or the axle itself. Most trucks today weak link can be the OEM wheels or rear spring pack.

[MHay]

wing_zealot wrote:
Your WDH is moving 400 lbs of weight out of a total of 940 lbs. That's 42% which is pretty **** good. Your tongue weight is also 12.7% which is good also. The only thing you can do is try to shift 150 lbs of weight inside the trailer so it's off the tongue and onto the trailer axle. If you can't do that, then It's just to much trailer for that vehicle.

Thanks -- that's the confirmation I wanted to get.

I guess I'm still trying to understand how 1,000 lbs. is being added to the axle when the WDH bars are on despite tongue weight being 940 lbs.