How accurate are the truck scales.

Trackrig wrote:
I believe all scales used for commercial purposes have to be certified by the state they're in so they should be pretty close.

Bill

It depends on the state. It is also important to understand that the term "certified" is nothing more than a piece of paper that says on a certain date, a known weight was applied to the scale and the scale's displayed weight was within the range specified.

The intervals at which the scales are checked varies. But it is usually no more than a year. In many places, it's a much shorter interval.
As someone who works on scale systems, I have found one of the easiest ways to check for a problem is to check for repeat-ability.(more on that later)
The actual device that measures the weight is fairly accurate, it does not usually lose its "calibration". Usually the on;y thing that affects it's readings is large temperature variations. (which is why it is a good idea to have the scales calibrated every quarter)

In a sense, these scales nothing more than mechanical devices designed to transfer the weight applied to the deck to one or more load cells. The load cells put out (actually reflect) a voltage based on the deflection of the strain gauge. Depending on the type of array, the voltage signal from many load cells are combined at the summing board. That signal is then sent to the scale.
As with any mechanical device, it needs maintenance. That is where variations come up.
So the best way to rule out a general problem, is to reweigh. Most accuracy problems with the scales start with some sort of mechanical bind between the scale deck and the load cells. Simply pulling completely off, then pulling back on at a slightly different location on the scale deck will expose binding issues. If there is a bind, you will not get the same reading. If the reading is the same, it is likely a mechanically sound scale.

When I purchased the TT the dealer set the hitch ball height set the chain at 7 links for a level TT. He mentioned when it was loaded with our stuff and water I may have to go up a link.

Sure enough when the groceries, clothes, bedding and camp gear etc. were added; to sit level require another link. It pulls fine, is very stable. Even in the Rockies last summer I never felt uncomfortable. Of course I am older and not to likely to push the performance envelop. The 9 link experiment just to see what would happen.

However, on my recent trip to the Ozarks last month, I went overboard with canoe, camping and fishing gear piled on and into the TV. It was not the TT tongue weight so much as the extra gear that put me over my Max cargo.

If the WDH was shifting any weight back to the front axle (and I would guess it was since you lost only 60 pounds)) then your TW is higher than 500 pounds and 8%. Some of the TW is shifted to the TT axles. I would guess TW is more like 600-625 pounds.

TT levelness is adjusted by the hitch head height and independent of TW or TW %.

It looks like you have two passes, truck alone and truck with TT with WD. Once more pass preferably with the same loading can provide actual TW as well as how well the WDH is adjusted. The third pass is truck with trailer on ball, no WD.

For your use, + or - 50lbs is probably not going to matter, but repeatability will. If you just get your truck weighted and then want to go back with your trailer, best to go to the same scale for both and then you are not wondering how the scales are different.

I think 40 lbs. would be more than accurate enough. That is only about five gallons of water.

Just for the sake of information, I wanted to know the tongue weight with the WD hitch at 9 chain links.

Truck only with cap and 100 lb. payload; front 3480, rear 2820, TT none. Total 6300 lbs.

Truck with cap, 100 lb. payload, WD hitch and TT; front 3420, rear 3380 TT 5540. Total 12,340.

From this I found that the WD hitch shifted all but about 60 lbs. back to the front axle. The rear axle gained 560 lbs. So, the total truck weight increase was 500 lbs. and if I add the 5540 TT axel weight; the 6040 lb. TT only had about 8 % of its weight on the tongue. Which resulted in the TT being nose high.

On vacation with a canoe, fishing gear and additional camping gear, I adjusted the TT for level at 8 links and the tongue weight was at almost 11 percent.

That is why I was curious to see if the CAT scales were accurate enough for such calculations and they are.

Once when I weighed my pickup and fifth wheel, I stopped with the truck & trailer on the second and third scale, and I was standing on the first scale (where the front tires should have been). It was not intentional; I just stopped short. When I got the result, the second and third scales read 10,400 and 9,800. The first scale read 140 pounds. My weight at the time was very close to 140 pounds.

Trackrig wrote:
I believe all scales used for commercial purposes have to be certified by the state they're in so they should be pretty close.

Bill

X-2 The scales are accurate and are what the industry relies on. There are several factors that affect a vehicle weight, fuel load when weighted or ice/snow load in the winter.

I don't think its the "legal weight" issue here as not too many 5ers and travel trailers would approach that limit, maybe some coaches but.....Its more an issue of knowing you're within the TVs limits and margin of safety. Should one be in an accident that weigh slip just might save your butt. Being able to prove that you weren't overloaded could come in handy. Not to mention any warranty claims on a broken axle or differential.

CAT Scale Offers an Unconditional Guarantee

If you get an overweight fine from the state after our scale showed you legal, we will immediately check our scale. If our scale is wrong, we will reimburse you for the fine. If our scale is correct, a representative of CAT Scale Company will appear in court with the driver as a witness.

It’s that simple, and just another reason why we are your #1 choice.

We guarantee it all! That’s right! We guarantee axle weights to be accurate as well as the gross weight.



The STATE would swear in court that their scale was correct, the CAT representative would swear their's is correct. That gives the driver a 50/50 chance the fine is thrown out. Probably a higher percentage of dismissal without it, still nothing more than "experts" arguing, and a 3rd party deciding someone else's fate.

Having said this..... I have seen numerous post on here that say LEGAL WEIGHT doesn't matter to the RVer. Even suggesting another attempt to stay legal will have you be accused of being weight police.

SO....I would say that the CAT scale is "close enough" to give you an idea of what you are hauling.

rbpru wrote:
I took my F-150 to the local Pilot CAT truck scales, centered it between front and rear axle scales and was surprised to learn front was 3480 lbs. the rear was 2820 lbs. The bed had 100 lbs. of potting soil in it and a fiberglass topper.

So the question is, does the location on the scales effect the weight? I was an equal distance on each scale. Also, what is the plus/minus poundage tolerance on the weight.

I went to 3 scales once on the same day with our truck and trailer - 1 Cat scale and 2 commercial highway scales. All were the same within 40 lbs but this doesn't account for the weight of fuel I burned up driving between scales. On another occasion, I found a local grain elevator to be within 20 lbs of one of the above highway scales. These scales are surprisingly accurate considering the amount of weight they are weighing. Info on scale accuracy here: link

Did you calculate your actual payload capacity versus what is shown on the door pillar sticker? Sometimes there can be quite a difference.