This SAE Recommended Practice shall cover mechanical- readjust stroke indicators for actuators with visible exposed pushrods and electrical-readjust stroke indicators for all air-brake actuators. This device shall indicate the foundation brake(s) may require adjustment or service when inspected per vehicle manufacturer's procedures. A measurement shall be made to determine actual stroke measurement for any system not factory calibrated. Stroke indication accuracy of an air-brake actuator can be assured only when all of its components are supplied by the original brake actuator manufacturer.
This standard is being revised as part of the 5 year review process. Most of the revisions are updates to format and wording only. The tolerance for the placement of the stroke indicator band was changed to + 0.0 -3.8 mm (+0 -.15 in) tolerance instead of +0.0 to 3.8 mm (+0 to .15 in). The minus tolerance means the indicator will begin to show from readjust stroke (max.) to 3.8 mm (.15 in) before the readjust stroke is reached. The old tolerance would allow the indicator to begin showing at readjust stroke or up to 3.8 mm (.15 in) after readjust stroke has been reached. The minus tolerance does not reduce the effectiveness of the indicator, but the old plus tolerance may allow for reduced brake effectiveness beyond the stated readjust point.