How to Slide Tandems (and How Much Weight Moves)

Slide the trailer tandems forward, toward the tractor, to move weight off the drives and onto the trailer axles; slide them back to put weight on the drives. How much each hole moves depends on your trailer, load and hole spacing, so the helper below works it out from two of your own scale tickets.

How to slide tandems

1. Weigh first. Get a scale ticket and write down the steer, drive and trailer tandem weights.
2. Pick a safe spot. Pull onto level ground, out of traffic, where sliding is allowed.
3. Set the trailer brakes only. Pull the trailer air supply so the trailer wheels hold, with the tractor brakes released.
4. Pull the release handle. Pull the slider release handle and lock it open, then look to confirm the locking pins are out.
5. Move the tractor slowly. Backing up slides the trailer body back over its wheels, which moves the tandems forward. Pulling ahead moves them back. Count the holes.
6. Lock and look. Release the handle so the pins drop in, then get out and check that every pin is fully engaged.
7. Tug test. With the trailer brakes still set, gently pull against them to make sure the slider is locked.
8. Weigh again. Go back over the scale and check every axle, tandem and the gross.

Follow your trailer maker's and your company's procedure where they differ. Never stand near the wheels or between the tractor and trailer while the trailer is moving.

Slide helper

Weigh, slide a known number of holes, weigh again. The helper works out your own pounds per hole.

Ticket A (before sliding, lb)

Drive tandem

Trailer tandem

Ticket B (after sliding, lb)

Drive tandem

Trailer tandem

Holes moved between the tickets

Target for each tandem (lb)34,000 lb is the federal tandem limit (23 CFR 658.17(d)). Use a lower number if you want a margin.

Work it out

The fifth wheel works the same way

A sliding fifth wheel shifts weight between the steer and the drives. Sliding it forward adds weight to the steer and takes it off the drives; sliding it back does the opposite. Calibrate it the same way, with two tickets.

What you are aiming for

Federally, each tandem is limited to 34,000 lb, any one axle to 20,000 lb and the gross to 80,000 lb, and moving the tandems changes the spacing the bridge formula uses (23 CFR 658.17). Check the result in the axle weight calculator. Some states also limit kingpin-to-rear-axle distance.

FAQ

Which way do I slide tandems to take weight off the drives?

Slide the trailer tandems forward, toward the tractor, to move weight off the drives and onto the trailer axles. Slide them back, toward the rear of the trailer, to put weight on the drives and take it off the trailer tandem. Weigh again after every slide, because the load decides how much moves.

How much weight does one hole move?

There is no official number. It depends on the trailer, the load and how far apart the holes are, so a figure you read online may not match your trailer. The helper on this page works out your own pounds per hole from two scale tickets taken before and after sliding a known number of holes.

Is it legal to slide tandems all the way back?

Federal rules do not set a slide position, but some states limit the distance from the kingpin to the rear axle, and the bridge formula still applies to the new spacing. Check your state's rules for the roads you are running before you slide all the way back, and weigh again afterward.

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Sources

• 23 CFR 658.17, Weight (eCFR)
• FHWA, Bridge Formula Weights (FHWA-HOP-19-028)
• FHWA, state truck size and weight laws (Appendix B)

Disclaimer: For general information. Federal limits from 23 CFR 658 and 49 CFR; state limits, permits and enforcement vary. Check your state's CDL manual and DOT before you rely on a number. Not legal or tax advice.

Updated Nov 13, 2026. See something wrong? Tell me.