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MHay's avatar
MHay
Explorer
Aug 25, 2020

Help Deciphering CAT Scale Weights

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.
  • RobWNY's avatar
    RobWNY
    Explorer
    Aug 25, 2020
    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).
  • routeforty's avatar
    routeforty
    Explorer
    Aug 25, 2020
    Not an expert at this, but I think we need more info-truck size(1/2 ton 3/4 ton etc) load range of tires on truck and trailer, weight rating of axles and tires on trailer., For me all those weights would mean I'm good to go, but I have a diesel dually.
  • MHay's avatar
    MHay
    Explorer
    Aug 25, 2020
    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).

    Yeah, I'm not sure about that either. I just chalked it up to an accuracy issue with the scales.
  • MHay's avatar
    MHay
    Explorer
    Aug 25, 2020
    routeforty wrote:
    Not an expert at this, but I think we need more info-truck size(1/2 ton 3/4 ton etc) load range of tires on truck and trailer, weight rating of axles and tires on trailer., For me all those weights would mean I'm good to go, but I have a diesel dually.


    It's a 2020 Expedition Max.

    Payload: 1,700
    Front GAWR: 3,450
    Rear GAWR: 4,380
    GCWR: 15,200
    Max Trailer Weight: 9,000

    Notably the rear GAWR is exceeded in the current setup, which is the reason I'm asking if I can expect to be able to move more weight off the rear axle with a WDH.
  • Grit_dog's avatar
    Grit_dog
    Navigator
    Aug 25, 2020
    OP first realize it’s not an exact science and if it tows well Currently then it’s a good setup. Couple hundred lbs on any axle is not significant or really noticeable. If the front end isn’t floating and the back of the truck doesn’t need more weight removed (sagging) and it drives good, you’re good!
    I’m confuse though between pass 2 and 3 your trailer axle weight Should be very close to the same, whether the truck or the Jack is holding up the trailer tongue. Or is that the entire trailer weight in pass 3 including the jack?

    And yes it won’t hurt to take more weight off the rear of the truck. If you have reasonable capacity in your wdh.
    It also won’t hurt Your vehicle to leave it where it’s at.
  • MHay's avatar
    MHay
    Explorer
    Aug 25, 2020
    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.
  • wing_zealot's avatar
    wing_zealot
    Explorer
    Aug 25, 2020
    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.
  • RCMAN46's avatar
    RCMAN46
    Explorer
    Aug 25, 2020
    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).


    I will assume the OP used a CAT scale.

    CAT scale weights are in 20 lb multiples. If you look at the OP's weights they are in 20 lb multiples.

    I checked several of my CAT scale receipts and they were all in 20 lb multiples.

    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.
  • RobWNY's avatar
    RobWNY
    Explorer
    Aug 25, 2020
    RCMAN46 wrote:
    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).


    I will assume the OP used a CAT scale.

    CAT scale weights are in 20 lb multiples. If you look at the OP's weights they are in 20 lb multiples.

    I checked several of my CAT scale receipts and they were all in 20 lb multiples.

    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.

    That tells me the scales aren't calibrated. It shouldn't matter. A 20 pound increment transferred from one scale to a different scale because of a weight distribution system doing what they're supposed to do doesn't make the weight just disappear. it should take that 20 pounds from one scale and it should show up on another scale.
  • MHay's avatar
    MHay
    Explorer
    Aug 25, 2020
    RobWNY wrote:
    RCMAN46 wrote:
    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).


    I will assume the OP used a CAT scale.

    CAT scale weights are in 20 lb multiples. If you look at the OP's weights they are in 20 lb multiples.

    I checked several of my CAT scale receipts and they were all in 20 lb multiples.

    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.

    That tells me the scales aren't calibrated. It shouldn't matter. A 20 pound increment transferred from one scale to a different scale because of a weight distribution system doing what they're supposed to do doesn't make the weight just disappear. it should take that 20 pounds from one scale and it should show up on another scale.


    Yes, confirming it was a CAT scale.

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