When applying for oversized permits, accurate axle spacing measurements are essential. State regulations require precise distances between axles, as well as overall truck and trailer dimensions, to determine permit requirements. In this guide, we’ll walk you through the correct way to measure axle spacings, overall length, and kingpin to rear axle distances, ensuring that your permits are processed without delays. For a video walkthrough, you can also watch our tutorial here.
Why Accurate Axle Spacing Measurements Matter
For oversized and overweight loads, every state requires specific axle measurements to determine load distribution and weight compliance. The key measurements include:
- Axle-to-axle spacing – Distance between the center of each axle hub.
- Overall vehicle length – Total bumper-to-bumper measurement.
- Kingpin to rear axle – Critical for trailer stability and compliance.
Step-by-Step Guide to Measuring Axle Spacing
Before you begin, you’ll need:
🗸 Measuring tape (long enough for accurate readings)
🗸 Flags, sticks, or markers to mark axle hub centers
- Place a marker on the ground directly under the center of each axle hub, This makes it easier to measure accurately without estimating distances
Once the hubs are marked:
- Start from Axle 1 to Axle 2 – Measure from the center of one hub to the center of the next hub.
- Continue the same process for Axle 2 to Axle 3, Axle 3 to Axle 4, and so on.
- If your measuring tape is too short, break the distance into two sections, measure separately, and add the numbers together (A + B = Total Distance).
Pro Tip: Always record each measurement precisely and double-check before submitting permit applications.
Measuring Overall Vehicle Length
Another critical measurement is the total bumper-to-bumper length.
- Start from the front bumper of the truck and measure all the way to the rear bumper of the trailer.
- This must be a straight-line measurement from front to back.
- Include any load overhang if applicable.
Why It Matters: Oversized load permits often have maximum allowed lengths, and incorrect measurements could lead to violations or permit denials.
How to Measure Kingpin to Rear Axle Distance
This is one of the most important measurements for permits, and it’s required by most states.
Step 1: Identify the Kingpin
- The kingpin is the pin that locks into the fifth wheel of the truck.
- Place a marker directly under the kingpin.
Step 2: Measure to the Rear Axle
- Measure from the kingpin to the center of the last axle hub, This gives you the kingpin-to-rear-axle measurement
Finally, by following these guidelines we provided, you’ll avoid permit delays, prevent compliance issues, and ensure your oversized load is approved for transport.
