OOSC, Part II, Item 1. a. Defective Brakes - Inoperative Brake (PBBT Reading)

For several years the PPBT user’s forum has been discussing creating a wheel end criteria based off of PBBT tests when the brake output is 0, meaning the brake is not showing any brake force at all or completely inoperative. An adhoc committee was put together to discuss this topic in further depth at the Spring Workshop in New Orleans 2025. The committee met on 06/24/25, 09/03/25, and 09/18/2025 and was comprised of members from law enforcement, FMCSA, industry, and the PBBT vendors Link and NEPEAN (VIS). During the Denver Annual Conference in 2025, it was decided unanimously by the PBBT users group to submit an issue request to the vehicle committee for more consideration on a wheel end criteria. Dan Cleary from NEPEAN presented to the users group in Denver. Dan discussed the original specification for PBBTs dates back to 1998 and it has not been updated. A PBBT test is done at a low speed to capture the maximum brake force. Dan indicated rolling resistance was included in the NEPEAN test because it does contribute to stopping the vehicle. LINK does not and has never include rolling resistance in their calculation. After discussion, it was decided to request NEPEAN to show a 0-reading based solely on the brake force and remove the rolling resistance from the calculation. This decision was due to the brake force as being defined as: The force that the outer diameter of the tire imparts on the road surface as a result of the brakes being applied.

If an inspector cannot find the reason for the 0-reading for a completely inoperative brake, but the overall vehicle(s) passes 43.5, the vehicle has no violations and receives a CVSA decal and the vehicle can proceed with a clean inspection report. This only applies when the inspector cannot find the reason why the brake is completely inoperative. This is obviously in conflict with highway safety but is what is currently in practice.

The request would be that when the brake is completely inoperative and the test shows a 0- reading for brake force during a PBBT test, it could be documented as a violation and that wheel end would be included in the 20% brake criteria as one defective wheel end. Again, this will only apply when the inspector cannot find the reason why the brake is completely inoperative, and the test shows a 0-reading. In the cases where the inspector can find the reason for the inoperative brake, they can document the violation at the wheel end for that reason which is the current practice.