A truck on a weigh-scale platform at dusk, trailer tandems and chrome wheels lit by amber light

Tandem Slide Calculator

Scale ticket in, holes to slide out. Then reweigh.

Axle Weight & Tandem Slide Calculator

Enter your scale-ticket weights and get how many holes to slide the trailer tandems, and which way. A rule of thumb, not a substitute for the scale.

Pounds per hole

How sliding the tandems moves your weight

Sliding the trailer tandems is the fastest fix for an overweight axle, and it is also where a lot of drivers guess and then make a second trip across the scale. The mechanics are simple once you picture what is actually happening, and a calculator like this one turns your scale ticket into a specific move: which direction, and how many holes. What it cannot do, and what no calculator can do, is tell you that you are legal. Only the scale does that, which is why the one rule that never bends here is to reweigh after every slide.

Why sliding moves weight at all

Think of the trailer tandems as a fulcrum under a long load. The weight ahead of that fulcrum has to be carried somewhere, and it splits between the tandems and the kingpin, which sits over the tractor's drive axles. When you move the fulcrum, you change the split. Slide the tandems forward, toward the kingpin, and they sit closer to the bulk of the load, so they pick up more of it and the drives carry less. Slide them back, toward the rear, and they carry less while the drives carry more. Nothing is added or removed; weight just shifts between the two groups.

Which way to slide

That gives you a simple pair of rules. If your trailer tandems are heavy, slide them back to shed weight onto the drives. If your drive axles are heavy, slide the tandems forward to pull weight onto the trailer. The calculator reads your scale ticket, figures out which group is over, and tells you the direction and the number of holes to move. It also checks the group you are shifting weight onto, so it can warn you when fixing one axle would only push the other over, a sign that the freight itself needs to move.

Pounds per hole is an estimate

Each hole on the slider moves roughly a fixed amount of weight between the two groups. A common figure is about 250 pounds per hole, and some trailers move closer to 400. But this is genuinely a rule of thumb: the real figure depends on your trailer, its suspension, the load, and how the freight is stacked. That is why the calculator lets you choose 250 or 400 or enter your own number, and why the hole count it gives you is a starting point rather than a promise. Treat a two-hole answer as two holes, then verify.

What sliding cannot do

Sliding the tandems only rebalances the drives and the trailer tandems. It does not change your gross weight, so if you are over 80,000 pounds, no slide will save you; weight has to come off or move. It also does very little to your steer axle, which is adjusted mainly by the fifth wheel, a separate slide. When the calculator sees an over-gross ticket, it says so plainly rather than sending you sliding back and forth chasing a number you cannot reach.

Always reweigh

This is the part that keeps you out of trouble. A calculated slide gets you close, but a certified scale is the only thing that tells you the truth about your axle weights, and it is what enforcement reads. Make your move, pull back onto the scale, and confirm every group is legal before you head for the highway. This tool is an advisory aid to help you plan the move; it is not a compliance record, and it is not a scale.

Worked slide examples

Frequently asked questions

Which way do I slide the tandems to fix an overweight axle?
If your trailer tandems are overweight, slide them back toward the rear: that moves weight off the tandems and onto the drive axles. If your drive axles are overweight, slide the tandems forward toward the kingpin: that moves weight off the drives and onto the trailer tandems. The calculator tells you the direction and the number of holes for your scale ticket.
How much weight does one hole move?
It depends on the trailer, but a common rule of thumb is about 250 pounds per hole, and some trailers move closer to 400. The calculator lets you pick 250 or 400, or enter your own figure if you know your trailer. Because it is only an approximation, the number of holes is a starting point, and you must reweigh after every slide.
Why do I always have to reweigh?
Because pounds-per-hole is an estimate that changes with your specific trailer, suspension, load, and how the freight is stacked. A calculated slide gets you close, but only a certified scale tells you whether you are actually legal. Never take a calculated result on the road without confirming it on the scale.
Can sliding the tandems fix an overweight gross?
No. Sliding the trailer tandems only moves weight between your drive axles and your trailer tandems; it never changes your total gross weight. If your gross is over 80,000 pounds, no amount of sliding will help. You have to remove weight or redistribute it, and the calculator flags this case for you.
Does sliding the tandems change my steer axle weight?
Barely. The steer axle is adjusted mainly by the fifth wheel, which is a different slide. Moving the trailer tandems mostly rebalances the drives and the trailer tandems, so this calculator focuses on those two groups. If your steer axle is the problem, that is usually a fifth-wheel adjustment or a loading issue.
What are the legal axle limits?
Under the federal limits in 23 CFR 658.17, the maximum gross is 80,000 pounds, a single axle is limited to 20,000 pounds, and a tandem axle group to 34,000 pounds. Steer-axle limits vary by tire and axle rating and are often around 12,000 pounds. States and bridges can impose their own limits, so treat these as the federal baseline and check your route.