The Strategic Weight Bump
For savvy shippers and 3PL consultants, the NMFC Item 171 (Bumping Rule) is one of the few legal ways to manipulate freight class in your favor. Most shippers assume that less weight always equals a lower price. However, in density-based pricing, falling just short of a density threshold can leave you stuck in a much more expensive freight class. The Bumping Rule allows you to declare an artificially higher weight on your BOL to "bump" your shipment into the next density tier and secure a lower rate.
The Threshold Game
Freight classes change at specific PCF intervals (e.g., 6 PCF, 8 PCF, 10 PCF). If you are at 7.9 PCF, you are Class 125. If you bump to 8.0 PCF, you drop to Class 100.
Legal Compliance
Item 171 is an official NMFTA rule. You aren't "tricking" the carrier; you are officially declaring a higher weight to access a density-based incentive rate.
Math Example: How Bumping Saves Money
Shipment A: 720 lbs | 100 Cubic Feet | 7.2 PCF
Actual Class: Class 125
Rate: $1.50/lb = $1,080
Strategy: Bump to 800 lbs to reach 8.0 PCF.
New Class: Class 100
New Rate: $1.10/lb (Hypothetical Class 100 rate)
Final Cost: 800 lbs × $1.10 = $880
Total Savings: $200 by declaring 80 lbs of "ghost" weight.
Strict Rules for Bumping
You cannot use the bump rule for everything. It strictly applies to commodities with sub-provisions that explicitly mention density-based tiers. You must also declare the "Bumping Rule" on the original Bill of Lading. You must state both the actual weight and the "declared weight" necessary to achieve the lower class. If you don't document it correctly, the carrier will re-rate you back to your actual weight and higher class.
Find Your Bumping Point
Are you dangerously close to a density threshold? Use our calculator to find your exact PCF and see if a "bump" could save you hundreds.
Calculate Density Tiers ⟶