Mismatched LS and SS Brake Chambers on the Same Axle

Research pertaining to mismatching LS and SS brake chambers on the same axle resulted with two sources of information addressing this issue. The one source being The Maintenance Council (TMC) through their Recommended Practice Bulletin RP 635 (copy attached) recommends not to mismatch LS and SS brake chambers on the same axle as this could cause brake imbalance and system interference (page RP635-4). The second source Haldax (recently acquired Holland/ Anchorlok) through their Service Bulletin relative to Spring Brake Identification (copy attached) contains a warning to never interchange LS components with SS components as performance and stroke may be seriously affected. Part 396.3 (a) (1) FMCSR indicates all carriers shall maintain parts and accessories in a safe and proper operating condition at all times.

New Issue: With the new technology relative to LS chambers it appears from the research provided the issue of mismatched LS and SS chambers on the same axle needs to be addressed. Clarification: Clarification is sought to determine if Part 396.3 (a) (1) addresses the issue of mismatched LS and SS chambers on the same axle or, if this issue should be addressed through amendment to the regulation to include the new technology. Urgency: This issue needs to be addressed as there has been a least one incident and likely more. According to the information attached this would appear to be a safety

Request, if Part 396.3 (a) (1) addresses this type of infraction the defect be included in the OOSC as item 1. a (8) and be identified as one defective brake. Suggested wording could be" Mismatch long-stroke and standard-stroke brake chamber on the same axle". If applicable suggest this type of defect also be included in item 1.b. (2) (a) with suggested revised wording "Air chamber sizes including long-stroke and standard-stroke".