Proposed changes to brake readjustment limits published

The Federal Motor Carrier Safety Administration (FMCSA) has issued a proposed rule that would revise the clamp and rotochamber brake actuator readjustment limits in the Federal Motor Carrier Safety Regulations.

The proposal - issued in response to a request from the Commercial Vehicle Safety Alliance (CVSA) - would also clarify the application of the readjustment limits and correct an error in cross-referencing a manufacturing standard.

In early 2007, the CVSA asked for changes to the brake actuator stroke readjustment limits in 49 CFR Sec. 393.47(e), arguing that they were inconsistent with those found in:

- Appendix G, the annual (periodic) inspection standards.

- Society of Automotive Engineers’ (SAE) International Recommended Practice J1817 (SAE J1817), which is incorporated by reference under Sec. 393.47(e).

- CVSA's North American Standard Out-of-Service Criteria.

According to the CVSA, Sec. 393.47(e) “specifies readjustment (stroke) limits based on 80 percent of the rated (full) strokes listed in SAE J1817,” which causes discrepancies between the two standards. Consequently, “the enforcement and/or noting of Sec. 393.47(e) violations by cross-referencing the regulation to 80% of SAE J1817 … is proving problematic for inspectors and industry,” the CVSA wrote.

The FMCSA says the differences are only a small fraction of an inch, but acknowledged that they cause confusion and agreed to the recommended changes.

The agency did not, however, agree to another change the CVSA recommended. The CVSA pointed out that Sec. 393.47(e) considers a brake with the stroke at the readjustment limit to be out of adjustment. In contrast, both Appendix G and the OOS Criteria state that the brake travel must exceed the readjustment limit for the brake to be considered out of adjustment.

“An s-cam brake that is at the readjustment limit when it is cold will be beyond the readjustment limit when it gets hot,” the FMCSA noted. “FMCSA believes that vehicles should not be dispatched with brakes at the readjustment limit, because those brakes will be found to be beyond the adjustment limit - and out of compliance with the regulations - if evaluated during a roadside inspection after the brakes have become hot due to operational use.”

The proposed rule includes a revision to Appendix G to make it consistent with Sec. 393.47(e) on this issue, so that motor carriers take action when a brake is at the adjustment limit. In addition, the CVSA requested that FMCSA revise Sec. 393.53, Automatic brake adjusters and brake adjustment indicators, to reference the trailer manufacturing standards in Sec. 571.121.

FMCSA is accepting comments on the proposal until November 1, 2011.

Comments referencing docket number FMCSA-2010-0257 may be submitted online at