Gross Vehicle Weight vs. Axle Weight

Contents

• Gross weight
• Single and tandem axle weight
• Steer, drive, and trailer axle groups
• How cargo and equipment position affect distribution
• Why bridge formula still matters
• Sources

Gross weight

Gross vehicle weight is the total weight of the vehicle or combination at the time it is weighed. For a tractor-trailer, it is the sum of the steer, drive, and trailer axle readings shown on the scale ticket.

The federal Interstate gross limit for most combinations is 80,000 lb. This is a ceiling — a vehicle that passes all axle group checks but exceeds 80,000 lb gross is still overweight.

Single and tandem axle weight

Federal and state rules treat a single axle, a tandem axle group, and larger multi-axle groups as separate legal categories, each with its own limit:

• Single axle: 20,000 lb maximum under the federal Interstate framework.
• Tandem axle: 34,000 lb maximum per tandem group under the federal Interstate framework.

A truck can pass the gross weight check and fail an axle group check at the same time. This is one of the most common overweight situations in practice.

Example: A combination weighs 79,000 lb gross — under 80,000 lb. The scale ticket shows the drive tandem at 35,100 lb. The gross is fine; the drive tandem exceeds the 34,000 lb limit. The truck is overweight on the drive group despite passing the gross check.

Steer, drive, and trailer axle groups

Each axle group on a standard tractor-trailer has its own applicable limit:

• Steer: The front axle of the tractor. Compared to the single-axle limit and tire or equipment ratings.
• Drive: The tandem group under the tractor. Usually the heaviest group on a loaded combination. Compared to the tandem limit and bridge formula.
• Trailer: The tandem group under the rear of the trailer. Also compared to the tandem limit and bridge formula.

A scale ticket that shows steer, drive, trailer, and gross is providing four separate data points. Each one must be compared to the right legal category, not to each other.

How cargo and equipment position affect distribution

The weight on each axle group is not fixed. It shifts based on:

• Cargo position inside the trailer: Cargo loaded toward the front of the trailer adds weight to the drive axles. Cargo loaded toward the rear adds weight to the trailer axles.
• Fifth-wheel position: Sliding the fifth wheel forward adds weight to the steer axle and reduces drive weight. Sliding it back increases drive weight and reduces steer weight.
• Trailer tandem position: Sliding trailer tandems toward the rear reduces drive weight and increases trailer weight. Sliding them forward does the reverse.

These adjustments can sometimes bring an overweight axle group into compliance without removing cargo — but only if the total gross weight is also within the applicable limit. A re-weigh after any adjustment is the practical confirmation step before continuing.

Why bridge formula still matters

FHWA’s bridge formula connects axle spacing, axle count, and allowable weight. Even when steer, drive, and trailer axle groups are each individually within their limits, the spacing between groups can still produce a bridge formula violation for the full combination.

Read Bridge Formula Explained before treating any gross weight figure as the whole compliance answer. For worked numerical examples, see Bridge Formula Calculation Examples.

For a state comparison entry point, use Axle Weight Limits by State.

Sources

This page uses FHWA Federal Size and Weight Regulations and FHWA Bridge Formula Weights. State pages provide field-level state sources where reviewed.