Verification guide
CAT Scale Weighing Guide
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Quick answer
Weigh the rig loaded exactly as you travel. A CAT scale reports steer axle, drive axle and trailer axles separately, so one pass gives you loaded vehicle weight, trailer axle weight and axle loads. A second pass with any weight-distribution bars released and a third with the trailer uncoupled give you tongue weight by subtraction. Compare each figure with GVWR, front and rear GAWR, GCWR and the trailer’s GVWR.
What a scale actually confirms
A ticket gives you five things no estimate can: real loaded vehicle weight against GVWR, real front and rear axle loads against GAWR, real trailer weight against its own GVWR, real combined weight against GCWR, and — by subtraction — real tongue weight.
Why estimates drift
Percentage rules assume a typical weight distribution, and a trailer's tongue weight depends on where its axles sit and how it is loaded. Curb weights quoted online are often for a configuration that does not match your trim, drivetrain or options. Each error may be modest; stacked, they can be the difference between within the ratings and overloaded.
The three-pass method
Pass one: the whole rig on the scale, coupled and hitched exactly as you drive, so steer, drive and trailer axles all read at once. Pass two: the same, with any weight-distribution bars released. Pass three: uncouple, park the trailer clear, and weigh the tow vehicle alone. If you do not use a weight-distribution hitch, skip pass two. Ask for a re-weigh on passes two and three.
- Pass 1 gives axle loads as you drive, gross combination weight and trailer axle weight.
- Pass 2 gives the vehicle carrying the full tongue weight, with nothing moved by the bars.
- Pass 3 gives the vehicle without the trailer.
- Tongue weight = pass 2 vehicle total − pass 3 vehicle total.
- Loaded trailer weight = pass 1 total − pass 3 vehicle total.
Reading the ticket against your ratings
Take five numbers off the labels first: GVWR, front GAWR, rear GAWR, GCWR, and trailer GVWR. Then line each up against the ticket. Record the margin on each line rather than a simple pass or fail — the size of the margin tells you how much room you have for the gear you have not packed yet.
Using the scale to set a weight-distribution hitch
Compare the steer axle in pass three (uncoupled), pass two (bars released) and pass one (bars tensioned). The bars should restore the share of the front-axle drop your vehicle maker specifies; Ford specifies 50% for the F-150. If the front recovers too little, add tension; too much, back it off. This turns hitch adjustment from guesswork into a measurement.
When to weigh again
After any significant change: a new trailer, a new tow vehicle, a bed toolbox, a generator, a different loading routine, or a long trip with full tanks when you usually travel empty. For a rig that stays the same, once a season is a sensible habit.
Worked example
Worked example (hypothetical): reading a three-pass ticket
A half-ton and a travel trailer with a weight-distribution hitch, weighed loaded for a trip. GVWR 7,100 lb, front GAWR 3,700 lb, rear GAWR 4,100 lb, GCWR 15,000 lb, trailer GVWR 7,600 lb. All figures are illustrative.
| Line item | Weight | Where the number comes from |
|---|---|---|
| Pass 1 — steer axle | 3,180 lb | Against 3,700 lb front GAWR: 520 lb margin |
| Pass 1 — drive axle | 3,760 lb | Against 4,100 lb rear GAWR: 340 lb margin |
| Pass 1 — trailer axles | 6,140 lb | Bars tensioned |
| Pass 1 — vehicle total | 6,940 lb | Against 7,100 lb GVWR: 160 lb margin |
| Pass 2 — vehicle total, bars released | 7,000 lb | Carrying the full tongue weight |
| Pass 3 — vehicle alone | 6,050 lb | Trailer uncoupled and parked clear |
| Tongue weight | 950 lb | 7,000 − 6,050 |
| Loaded trailer weight | 7,030 lb | 13,080 − 6,050, against 7,600 lb trailer GVWR |
| Gross combination weight | 13,080 lb | Against 15,000 lb GCWR: 1,920 lb margin |
Every rating passes, but the margins are uneven: 1,920 lb spare on GCWR and only 160 lb on GVWR. The tongue weight came out at 13.5% of the loaded trailer. Subtracting pass 3 from pass 1 instead would have given 890 lb, 60 lb low, because the tensioned bars had moved that much onto the trailer axles.
What to compare on the ticket
| Ticket figure | Compare against | Where the rating is printed |
|---|---|---|
| Steer axle weight | Front GAWR | Certification label, door jamb |
| Drive axle weight | Rear GAWR | Certification label, door jamb |
| Vehicle total, coupled | GVWR | Certification label, door jamb |
| Trailer axle weight + tongue | Trailer GVWR | Trailer data plate |
| All axles combined | GCWR | Owner’s manual or towing guide |
| Tongue weight by subtraction | Hitch tongue rating | Label on the receiver |
| Axle weight vs tire capacity | Tire load rating | Tire sidewall and door label |
Record the margin on each line, not just pass or fail. A 100 lb margin and a 2,000 lb margin are very different situations.
Frequently asked questions
How do I measure tongue weight at a scale?
Weigh the tow vehicle with the trailer coupled and any weight-distribution bars released, then weigh the tow vehicle alone with the trailer uncoupled. The difference between the two vehicle totals is the tongue weight. With the bars tensioned the difference reads low, because part of the tongue load has moved to the trailer axles.
What does a CAT scale weigh session cost?
Prices are posted at each scale and vary by location. CAT scales offer a re-weigh on the same visit at a lower price than the first weigh, which keeps the multi-pass method cheap; ask for a re-weigh on the second and third passes.
Should I weigh with full or empty tanks?
Weigh the rig exactly as you travel. If you normally leave with a full fresh-water tank, weigh it full: water is 8.34 lb per US gallon, so a 40-gallon tank is 334 lb, and if the tank sits ahead of the trailer axles it raises tongue weight.
What do the three platform readings mean?
Steer axle is the tow vehicle’s front axle, drive axle is its rear axle, and the third platform reads the trailer axles. Their sum is the gross combination weight to compare with GCWR.
Why does my front axle get lighter when I hitch up?
Tongue weight sits behind the rear axle, which levers weight off the front. A weight-distribution hitch restores it. Comparing the steer-axle figure coupled and uncoupled shows exactly how much was transferred.