The MEI Self Setting Slack Adjuster (S-ASA) is a development of the ASA and offers various technical advantages.
The most obvious difference to the ASA is that the control arm of the S-ASA can be fixed to the anchor bracket at any point within its arc of rotation (-16 to +130 degrees).
This makes the S-ASA easier to fit than the ASA because there is no need to ensure that the control arm of the S-ASA is rotated to its maximum point of rotation before fixing it. This eliminates a major source of error at the point of fitment.
It also means that one S-ASA reference can be used in place of more than one ASA reference: one variable S-ASA control arm replacing a series of fixed ASA control arms - thus allowing a range reduction.
However, although superficially the same as the ASA, the internal mechanism of the S-ASA is different to that of the ASA and three major benefits follow from these differences:
Firstly, the 'o' ring and gasket seals that prevent ingress of dirt and moisture are even more effective than those of the ASA.
Secondly, the S-ASA design does not employ a one way clutch spring which is the eventual point of failure in most ASAs.
Thirdly, the rate at which the S-ASA adjusts is more sensitive and gradual than in the ASA, thus avoiding over adjustment into a drum expanded by heat and therefore achieving optimal lining to drum clearance.
Hover over the image below to see an exploded view of the MEI Self Setting Slack Adjuster.