Sliding Tandems for Weight Distribution

Each pin hole on a trailer tandem slider shifts approximately 400-500 lbs of weight between the drive axles and the trailer axles. The holes are spaced roughly 6 inches apart. Moving 5 holes (about 30 inches) shifts approximately 2,000-2,500 lbs. The exact amount varies based on load distribution, trailer length, and fifth wheel position.

If your drive axles are overweight and your trailer axles are light, slide the trailer tandems BACKWARD (toward the rear of the trailer). This moves weight off the drive axles and onto the trailer axles. Remember: wherever the tandems go, the weight follows them away from there — slide back, weight moves to trailer; slide forward, weight moves to drives.

Yes. Many states have bridge laws that limit the distance between the kingpin (fifth wheel) and the rear axle of the trailer. California requires a maximum of 40 feet kingpin to rear axle. Other states have different requirements. Sliding tandems too far back may put you in violation of bridge laws even if your axle weights are legal.

Weigh first, then slide if needed. Get your initial weights at a CAT Scale, determine which axle group needs adjustment, slide the appropriate number of holes, then reweigh to confirm. The $3 reweigh fee is worth the confirmation. Never assume the weight shift was correct without verifying on the scale.

Frozen tandem pins are common in winter and after long highway runs. The wrong move is to repeatedly slam the trailer brakes and rev the engine — that bends pin assemblies and can crack the slider rail. The right sequence: (1) Confirm trailer brakes are set, tractor brakes released, and the pin handle is fully pulled out and locked back. (2) Apply firm steady pressure forward against the trailer in low gear; if the pins don't release in 3-4 seconds, stop. Don't keep grinding. (3) Reverse 1-2 feet to relieve pressure on the pins, then try again. (4) If still stuck, get out and check the pin handle is actually locked — most 'frozen pin' calls turn out to be a partially-engaged handle. (5) WD-40 or PB Blaster sprayed directly into the pin holes from below works on actually-frozen winter pins; let it sit 5 minutes. (6) Last resort, tap the handle linkage gently with a rubber mallet — never a steel hammer. If pins still won't budge after all that, the slider mechanism likely needs a shop visit. Forcing them risks a $1,500+ slider rail repair.

Most class 8 box trucks (24-26 footers) have fixed axles, not sliding tandems — weight distribution is managed by where you stack the load inside the box, not by adjusting the chassis. Step-deck trailers DO have sliding tandems, and the rules above apply, but two things differ from a standard 53' van: first, the deck transition (where the high deck steps down to the low deck) creates a natural weight concentration point that limits how far back you can slide before the load itself becomes the constraint. Second, oversize loads on step-decks frequently require permits that lock your tandem position — a 12' wide load with a permit specifying 'tandems no more than 36 feet from kingpin' means you can't simply slide back to balance axles, you have to repack. Flatbeds with spread-axle configurations (10' axle spread vs the standard 4'-6') are governed by federal bridge formula rather than typical 34,000 lb tandem rules — they can carry up to 40,000 lbs on the spread axle group, and you don't slide them at all. Always check your trailer type before assuming the standard 53' van sliding-tandem rules apply.