Axle Balance How to slide tandems

How to slide your tandems (and your fifth wheel)

The quick rules, the steps, and how to know how many holes to move

The rule: move the trailer tandems forward to take weight off your drives and put it on the trailer tandems. Move them back to do the opposite. Slide the fifth wheel forward to put more weight on the steer axle, or back to take weight off the steer and put it on the drives.

Which way to slide

Problem on the scale ticket	Fix
Drives over 34,000 lb, trailer tandems light	Slide trailer tandems forward (toward the nose)
Trailer tandems over 34,000 lb, drives light	Slide trailer tandems back (toward the doors)
Steer axle too heavy	Slide the fifth wheel back
Steer light, drives heavy	Slide the fifth wheel forward (watch steer limit and bridge)
Both tandems heavy	Sliding can't fix it: the load is too heavy. Rework the load.

Moving the trailer tandems toward the kingpin puts them more directly under the heavy part of the load, so they carry more of it and the drives carry less. Sliding them toward the rear lengthens that distance, so more of the trailer's weight rides on the fifth wheel and your drives.

Step by step

Weigh on a certified scale and keep the ticket. You need steer, drive and trailer tandem weights.
Decide which way to go. Too heavy on the drives: move the tandems forward. Too heavy on the trailer tandems: move them back.
Pull to a safe, level spot off the scale. Set the trailer brakes (red knob pulled) and keep the tractor brakes released.
Pull the slider release handle and make sure the locking pins come all the way out. Rock the tractor gently if they stick.
Back up slowly to move the tandems forward under the trailer, or pull forward to move them back. Count the holes as you go.
Release the handle and confirm every pin is locked through the rail. Do a tug test against the trailer brakes.
Check that you haven't gone past the state's kingpin-to-rear-axle limit, then re-weigh to confirm.

"Back up" and "pull forward" can feel backwards the first few times. With the trailer brakes set, the tandems stay put on the ground, and the trailer box slides over them. Backing the tractor pushes the box back, which moves the tandems forward under it.

How many holes to move

How much weight moves per hole depends on how much is in the trailer and where it sits. A heavy load moves more per hole than a light one. Axle Balance estimates the change for your load, tells you the hole count, and learns your real per-hole rate every time you log a scale ticket.

Don't slide past the legal limit

Many states limit the distance from the kingpin to the rear axle or the center of the rear tandem on 53 ft trailers, from 40 ft to 45 ft 6 in depending on the state, most often 41 ft. Sliding the tandems all the way back can put you over it. Check the tandem hole rules for every state before you slide back for weight.

Remember the bridge formula

Sliding tandems also changes the distance between your axle groups, which can change your legal weight under the federal bridge formula. On a 5-axle rig, the drive and trailer tandems can each carry 34,000 lb when the first and last axles of those tandems are at least 36 ft apart (FHWA). More in the bridge formula guide.

Know which way to slide before you get back on the scale. Axle Balance is a free calculator made by a trucker. Enter your scale ticket and it tells you which way to slide your tandems and how many holes, plus your fifth wheel. Works offline in the cab.

Open the free calculator

Estimates and general information only, not legal advice. Laws change and enforcement varies. Always confirm on a certified scale and with the state before you rely on it. See the Terms of Use.