CAT Scale vs Certified Scales: How to Weigh Your Truck
Knowing your gross and axle weights before you roll is one of the cheapest insurance policies in trucking. This guide covers when to weigh, how CAT Scale works, reading a ticket, and sliding your tandems to fix an overweight axle.
Quick Answer
A CAT Scale is a private, certified scale at thousands of truck stops where you pay roughly $13–$15 to weigh and about $3–$4 to reweigh the same day. It tells you your gross weight and weight on each axle group so you can fix an overweight problem — by sliding your tandems or fifth wheel — before a state weigh station finds it. Uncertified lot scales can give you a rough number, but only a certified scale produces a ticket you can stand behind. Find one near you in our truck scales directory.
Why and When to Weigh
A loaded tractor-trailer in the U.S. and Canada is generally capped at 80,000 pounds gross combination weight on the Interstate system without a permit. Hit that number on a state scale and you are looking at fines that climb fast — many states charge per pound over, and a few hundred pounds over a single axle limit can cost more than a tank of fuel. Weighing first turns a potential citation into a 15-minute fix.
Weigh when any of these is true:
- ✓You loaded heavy freight. Anything near max payload — beverages, paper, steel, liquids, canned goods — deserves a scale ticket before you leave the shipper's area.
- ✓You did not see the load. Drop-and-hook or a pre-loaded trailer means you are trusting someone else's count and placement.
- ✓The freight could have shifted. Partial loads, rolling product, or a load that settled in transit can push one axle group over.
- ✓You are crossing into a state with aggressive enforcement. If your route runs past open weigh stations, a $14 ticket beats a roadside fine and a delay.
You want two numbers: your gross (everything together) and your per-axle weights (steer, drives, trailer tandems). A truck can be legal on gross and still be over on the drives or trailer because the load is sitting in the wrong place.
Bridge Law and Axle Limits
Federal limits for a standard five-axle rig are straightforward to memorize: 12,000 lb on the steer axle, 34,000 lb on the drive tandems, and 34,000 lb on the trailer tandems, with an 80,000 lb ceiling overall. Many steer axles and tires are actually rated higher, and some states allow up to 12,000–13,200 lb on the steers, but 12,000 is the safe planning number.
The Federal Bridge Formula is the wrinkle that catches new drivers. It limits how much weight you can carry on a group of axles based on how far apart those axles are spread. The tighter your axles are bunched together, the less weight that group is allowed to carry, because closely spaced heavy axles stress a bridge deck more. This is exactly why your trailer tandem position matters: sliding the tandems does not just shift weight between axle groups, it can also change whether you are bridge-legal at all.
In practice, you do not have to do the math on the shoulder. Stay under the per-axle limits, keep your tandems in a reasonable spread, and weigh. If your steer, drives, and trailer are each legal and your gross is under 80,000, you are almost always fine.
How a CAT Scale Works
CAT Scale operates a network of certified scales at truck stops across North America. The platform has separate weigh pads so it can capture each axle group individually. Here is the routine:
- Pull onto the scale so your steer axle sits on the first pad, drives on the second, and trailer tandems on the third. Get the truck straight and fully on.
- Press the call button and tell the cashier your truck and trailer number. Or skip the intercom entirely with the Weigh My Truck app, which lets you pay and pull your ticket from the cab.
- Wait for the weights to register, then pull forward and park.
- Collect your ticket inside at the fuel desk, or get it instantly in the app.
A first weigh runs about $13–$15 depending on location. If you need to slide tandems and check again, a reweigh on the same scale, same day, same truck is only about $3–$4 — keep your first ticket and tell the cashier it is a reweigh. The Weigh My Truck app handles the reweigh discount automatically.
CAT backs its scales with the CAT Scale Guarantee: weigh legal on their certified scale, and if you still get an overweight ticket from an enforcement scale for the same weights, they will work with you to resolve the fine. That guarantee is the whole reason the certified ticket is worth more than a guess.
Reading Your Weight Ticket
A CAT ticket breaks your rig into three numbers plus the total. Here is what a typical legal five-axle ticket looks like and how to read it.
| Position | Example Weight | Federal Limit |
|---|---|---|
| Steer axle | 11,800 lb | 12,000 lb |
| Drive axles | 33,600 lb | 34,000 lb |
| Trailer axles | 33,400 lb | 34,000 lb |
| Gross | 78,800 lb | 80,000 lb |
That ticket is clean: every axle group is under its limit and the gross has room to spare. The number to watch is rarely the gross — it is the gap between your drives and your trailer. If your drives read 34,500 and your trailer reads 32,000, you are over on the drives even though your gross is fine. That imbalance is what you fix by sliding tandems.
The ticket also prints the date, time, location, and scale number. Hang onto it. If you reweigh, the cashier needs the original to give you the discount, and the dated ticket is your documentation if you roll across a scale later.
Fixing an Overweight Axle
You have two adjustments: the trailer tandem slide and the fifth wheel slide. Most of the time you will use the trailer tandems.
Sliding the Trailer Tandems
Sliding the tandems changes where the trailer's weight is supported. Move the tandems back (toward the rear) and you take weight off the trailer axles and put it onto the drives. Move them forward (toward the nose) and you do the opposite — weight comes off the drives and lands on the trailer. Each pin hole on a typical 53-foot trailer shifts roughly 250 to 500 pounds per axle group, so it is a fine adjustment, not a sledgehammer.
Tandem slide cheat sheet
- •Drives heavy, trailer light: slide tandems forward to load the trailer.
- •Trailer heavy, drives light: slide tandems back to load the drives.
- •Remember bridge law: sliding tandems all the way forward can put you out of legal axle spacing in some states even if the weights look good.
The mechanics: park on level ground, set the trailer brakes, release the slide pins (manual handle or air-release valve), then bump the tractor forward or back in low gear to walk the trailer on its locked tandems. Re-seat the pins, tug-test to confirm they locked, and raise the landing gear if it was down. Then reweigh.
Sliding the Fifth Wheel
The fifth wheel shifts weight between your steer and drive axles. Slide it forward to put more on the steers, back to take weight off them. Use it when your steers are heavy or light but the trailer is fine. Most drivers leave the fifth wheel set and solve weight problems at the tandems, but knowing both gives you full control over how the load sits.
Certified vs Uncertified Lot Scales
Not every scale on a truck stop lot is the same animal. A certified scale — like CAT — is inspected and tested for accuracy by state weights-and-measures officials, and it produces a legal-weight ticket. An uncertified lot scale, sometimes found at warehouses, grain elevators, or some terminals, gives you a number but is not held to the same accuracy standard and the ticket carries no weight as documentation.
Uncertified scales have their place. If a shipper has a wheel scale or a platform scale on site, it is great for a rough check before you leave so you know whether you even have a problem. But before you bet a fine on your weights, get onto a certified scale. The difference in cost is a few dollars; the difference in confidence is the CAT guarantee versus a shrug.
Browse certified and self-service scales near your route in the NearbyTruckStops scales directory, and check amenities at the stop while you are there with our truck stop amenities comparison.
CAT Scales vs Weigh Stations
These two get confused, but they serve opposite purposes. A CAT Scale is voluntary and on your side: you pay to learn your weights so you can fix problems privately. A weigh station is run by the state for enforcement — officers compare your weights to legal limits and can write tickets, order you to shed weight, or place you out of service.
| Factor | CAT Scale | Weigh Station |
|---|---|---|
| Purpose | Self-check before you drive | State enforcement |
| Cost to you | ~$13–$15 (reweigh ~$3–$4) | Free to pass, costly if over |
| Outcome if overweight | Slide tandems and fix it | Fine, delay, or out-of-service |
| Documentation | Certified ticket + guarantee | Citation if in violation |
The smart play is simple: if you are running heavy and a weigh station is ahead, weigh at a CAT Scale first. A few dollars and fifteen minutes buys you certainty that you will roll across the state scale legal.
Frequently Asked Questions
How much does it cost to weigh at a CAT Scale?
What is the difference between a CAT Scale and a weigh station?
Is a CAT Scale weight legal proof of my weight?
How do I fix an overweight drive or trailer axle?
Find a Certified Scale Near You
Browse certified truck scales along your route and weigh before you reach the next open weigh station.