Tandem Slide Calculator
Type in the three weights off your scale ticket. Get how many holes to slide, which direction, and what your axles will weigh after the move — before you pay for a reweigh.
Enter your weights and hit WEIGH IT
How the tandem slide math works
Sliding your trailer tandems moves weight between your drive axles and your trailer tandems — it never changes your gross. Slide the tandems forward (toward the cab) and weight comes off the drives onto the tandems. Slide them back (toward the rear) and weight moves off the tandems onto the drives.
≈ 250 lb/hole on 4″ centers · ≈ 400 lb/hole on 6″ centers
Example: drives at 35,120 lb are 1,120 lb over the 34,000 limit. On 4″ holes that's 1,120 ÷ 250 = 4.5, so slide 5 holes forward. Your drives land around 33,870 lb and the 1,250 lb moves to the trailer tandems — the calculator checks they stay legal too.
Limits used: 12,000 steer · 34,000 drives · 34,000 tandems · 80,000 gross (federal Interstate limits). Watch state bridge law — California, for example, limits kingpin-to-rear-axle to 40 feet, which can cap how far back you can slide.
FAQ
Which way do I slide if my drives are heavy?
Forward, toward the cab. The tandems move closer to the freight, so they pick up weight and your drives shed it. Tandems heavy? Slide back, toward the rear.
How much weight is one hole worth?
Rule of thumb: about 250 lb per hole on 4″ centers, about 400 lb on 6″ centers. Trailers vary — check your rail. When in doubt, slide one extra hole and reweigh.
What are the legal axle limits?
Federal Interstate limits: 12,000 lb steer (typical tire rating), 34,000 lb drive tandem, 34,000 lb trailer tandem, 80,000 lb gross. Some states allow more off the Interstate; bridge law adds spacing rules.
I'm over gross. Can sliding fix it?
No. Sliding only redistributes weight between axle groups. Over 80,000 gross means dropping freight, burning fuel weight, or an overweight permit.