Semi Truck Weight Adjusting – How to Balance Axles Safely

A complete guide on how to adjust weight on a semi-truck using tandem slides, fifth wheel adjustments, suspension controls, and safe load positioning techniques.

📅 Published on 2025-12-17 | ✍️ Semi Trailer News Technical Desk

Image: Driver checking axle weights on a semi-truck

Balancing weight on a semi-truck is one of the most critical tasks for safe and legal operation. Incorrect axle weights can lead to steering loss, reduced braking efficiency, excessive tire wear, DOT violations, and dangerous trailer sway.

This guide explains exactly how drivers adjust weight using tandem slides, fifth wheel adjustments, suspension systems, and proper cargo placement.

1️⃣ Why Weight Adjustment Matters

Every axle on a semi-truck has a legal limit. Even if the total weight is under 80,000 lbs, the truck can still be illegal if one axle group exceeds its limit. Proper weight distribution ensures:

• stable steering on highways
• even tire wear
• maximum braking performance
• fuel efficiency
• safe cornering and reduced rollover risk

2️⃣ Standard Axle Weight Limits (U.S. Federal Guideline)

• Steer axle: 12,000 lbs
• Drive axles: 34,000 lbs
• Trailer tandems: 34,000 lbs
• Total GVWR: 80,000 lbs

The most common overweight problems come from incorrectly loaded pallets or improper tandem positioning.

3️⃣ Methods to Adjust Weight on a Semi-Truck

🔸 Sliding the Fifth Wheel

This moves weight between the steer axle and drive axles.

• Move forward → increases steer axle weight
• Move backward → increases drive axle weight

🔸 Sliding the Trailer Tandems

This controls the balance between drive axles and trailer axles.

• Move tandems forward → more weight on trailer axles
• Move tandems backward → more weight on drives

🔸 Adjusting Load Placement Inside the Trailer

Drivers and loaders must position heavy cargo centered and low. Uneven side loading leads to sway and rollover risk.

4️⃣ Signs of Incorrect Weight Distribution

• Steering feels too light or heavy
• Trailer swing during turns
• Slower braking response
• Drive wheels losing traction
• Excessive tire heat

5️⃣ How Air Suspension Helps Balance Weight

Modern air suspensions automatically equalize weight between axles, but drivers must still:

• check air gauge readings
• ensure equal pressure between bags
• avoid overload even with air assist

Air suspensions help but do not override axle weight laws.

6️⃣ Final Checklist Before Hitting the Road

• Verify axle weights on a certified scale
• Check suspension leveling
• Ensure load is centered and secure
• Confirm tandems are locked in place
• Double-check gross vehicle weight

Proper weight adjustment protects equipment, improves fuel economy, ensures legal compliance, and keeps drivers safe on the road.

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