CAT Scale discrepancy

[ttavasc]

We took delivery last week of a new Jay Flight SLX 195RB Baja. Upon leaving the dealer I swung by the CAT scale to get an empty weight on the trailer before we start loading it up. I had previously weighed the TV with just myself and a full tank of fuel with the following results:

Steer Axle - 3440
Drive Axle - 2580
Total - 6020

Here are the weights with the TT attached but without WD engaged - includes battery and full 30lb propane tank (and unknown to me at the time a full fresh water tank ):

Steer Axle - 3320
Drive Axle - 3320
Total TV - 6640

Trailer Axle - 3020
GCW - 9660

I thought the TV numbers with the TT attached looked high and upon closer inspection of the TT I discovered the dealer sent me off with a completely full fresh water tank which sits all the way forward in the box. I have a Sherline Tongue scale so I used that to measure the tongue weight at the coupler with the trailer level. That came out to 420lbs. My hitch set-up is 60lbs.

So I'm trying to understand why the Total TV is ~160lbs more than what I would expect given the Sherline scaling the tongue at 420lbs. Also, a couple of weeks ago I hauled a bunch of scrap to the metal recycler. The scale there weighed my TV at 6000 on the way out which seems to agree with the first scaling of the empty TV at the CAT scale.

I've heard that the CAT scales are usually set for 20lb increments but sometimes are changed to use larger increments. It was a pretty busy day and I had to wait for a number of big rigs to roll through before I got my turn . Is it possible that a larger scale increment could cause the discrepancy? I don't see anything on the scale ticket that would indicate what increment it was calibrated for so I'm guessing one would need to ask the scale operator about that.

Given that the fresh water tank was full this scaling really isn't useful for me and I am planning to make another pass with the tank empty in order to get the proper baseline. But I do want to make sure I understand how to interpret the CAT scale values properly. At this point I think I am trusting the Sherline scale for an accurate tongue weight which is why I got it in the first place.

Appreciate any input or advice regarding this. Thanks!

[Grumpy]

In a way it was good that the fresh tank was full at least you know the dealer tested everything. Just forgot to empty it.

[RedHorse1]

Were you alone when you weighed the TT/TV combination? It does look like the numbers don't line up very well. The 420 from the tongue scale is real close to the 15% we'd expect. Not sure about different sensitivity on the scale but I'd expect not. I'd assumed the scale read in 10# increments but not really sure.
Was it the same scale for both weighings? Interesting to see what the weighing shows.

[ttavasc]

Originally Posted by RedHorse1

Were you alone when you weighed the TT/TV combination? It does look like the numbers don't line up very well. The 420 from the tongue scale is real close to the 15% we'd expect. Not sure about different sensitivity on the scale but I'd expect not. I'd assumed the scale read in 10# increments but not really sure.
Was it the same scale for both weighings? Interesting to see what the weighing shows.

Yes - I weighed the TT/TV combo using the same scale as the empty TV and with the same load criteria for the TV as in the first TV-only scaling - mainly nothing but myself and a full tank of fuel as I would drive from the pump to the scale after topping off.

I've done some more searching this afternoon trying to find where I had read about the different increments. While I didn't find what I had originally read I did see other posts that concurred with some scales using a larger increment amount such as 100lbs. If that was the case then it could account for the apparent discrepancy as it could be as much as 198lbs higher for the TV.

I may look around for another place to weigh. While this CAT scale is really convenient it's also pretty busy most of the time and may not be the best choice for my needs.

[Seann45]

Did you have the same amount of fuel in the tow vehicle both times?

[ttavasc]

Originally Posted by Seann45

Did you have the same amount of fuel in the tow vehicle both times?

Yep - same amount of fuel. The scale is the other side of the lot from the fuel pumps so I top off the tank and then go over to the scale.

[Subaru297]

If you can find a quiet time to go back to the scale and weigh just your trailer tongue while it sits on the Sureline and the scale at the same time that would be interesting. Or weigh something of a known weight to test your Sureline.
If everything was the same then one of the scales has to be off.
Assuming the CAT scale was zeroed each time and there was no mud sitting on it from a big rig it should be accurate. They must be maintained to a certain accuracy standard.

Cheers

[ttavasc]

Originally Posted by Subaru297

Or weigh something of a known weight to test your Sureline.

I did weigh something of known quantity on the Sherline - mainly myself. It was accurate compared to the what I weighed on the bath scales beside it. So I'm pretty comfortable with the Sherline at this point. I am planning on making another run to the scale after I empty the fresh water tank and make a couple adjustments to the hitch. Just not sure if I'll go back to that one or try another one that's not that much further away.