Tandem Slider Helper
Enter your scale weights and current tandem position to get a directional estimate on which way to slide.
Inputs
Recommendation
• Steer limit: 12,000 lb
• Drive limit: 34,000 lb
• Tandem limit: 34,000 lb
• Estimated shift: ~250 lb per hole between drives and tandems
• Sliding tandems will not fix an overweight steer axle
• Actual shift per hole varies by trailer — always verify on the scale
How Tandem Sliding Works
The tandem axle slider on a semi-trailer allows the rear axle group to be repositioned forward or backward along a rail. Sliding the tandems shifts weight between the drive axles and the trailer axles, helping drivers distribute load legally across all axle groups before hitting a scale.
Most trailers have tandem axle positions marked in increments of 4 inches, with anywhere from 10 to 20 holes depending on trailer length. Moving the tandems toward the front of the trailer shifts weight forward onto the drives. Moving them toward the rear shifts weight back onto the tandems.
Federal and State Axle Weight Limits
Federal bridge law sets the standard axle weight limits used in most states. The steer axle limit is 12,000 pounds, drive axles are limited to 34,000 pounds, and trailer tandem axles are also limited to 34,000 pounds. Gross vehicle weight cannot exceed 80,000 pounds on the Interstate highway system.
Some states have lower limits on certain roads and bridges. Always check state-specific rules when running off the Interstate, especially on state routes and county roads.
The 4-Inch Rule
As a general rule of thumb, sliding the tandem axles one hole (4 inches) transfers approximately 200 to 250 pounds between axle groups. This varies based on load distribution, trailer design, and cargo position. Use the calculator above for a more accurate directional estimate based on your actual scale weights.
Frequently Asked Questions
Which way do I slide my tandems to reduce drive axle weight?
Slide the tandems toward the rear of the trailer. This shifts weight back off the drives and onto the tandem axles. The calculator above will give you a directional estimate based on your actual weights.
Which way do I slide to reduce tandem axle weight?
Slide the tandems toward the front of the trailer. This moves weight forward onto the drive axles and off the tandems.
Can sliding tandems fix a steer axle problem?
No. Tandem sliding only redistributes weight between the drive axles and trailer axles. To fix a steer axle problem you need to reposition the cargo inside the trailer or adjust the fifth wheel position.
What is the kingpin to rear axle law?
Most states limit the distance from the kingpin to the center of the rear tandem axle group to 41 feet. This is a bridge law restriction. Exceeding it requires special permits in most states regardless of axle weights.