Air Brake Pushrod Stroke and Out-of-Service Screen

Whether a measured pushrod stroke is inside its chamber's readjustment limit, and whether the combination has enough defective brakes to be placed out of service. Each brake chamber has a published readjustment limit -- the stroke at which the brake is considered out of adjustment -- and it depends on the chamber type and size rather than on the vehicle: a standard type 30 clamp chamber sits at 2 inches and a long-stroke type 30 at 2.5 inches, so the limit is entered rather than assumed. Being AT the limit counts as defective, not merely being over it, which is the detail that turns a marginal brake into a violation. The vehicle-level rule is the one that decides whether the truck moves: when 20% or more of the combination's brakes are defective, the whole vehicle is out of service. On a five-axle combination with ten brakes, two defective brakes is exactly 20%, so a driver who finds one out of adjustment is one brake away from being parked, and three defective is 30% and the truck does not move until they are adjusted. Only at one defective brake, 10%, is the combination legal to operate, and it is a violation on the inspection report either way. That is the number worth knowing before the inspection rather than during it. A screen; the chamber manufacturer's published readjustment limit, the CVSA out-of-service criteria in full, and the inspector govern.

margin_in = readjustment_limit_in - measured_stroke_in; this brake is defective when measured_stroke_in >= readjustment_limit_in; defective_fraction_pct = defective_brakes / total_brakes x 100; out of service when the fraction is at or above 20%.

Pushrod stroke against the chamber's published readjustment limit (entered, not bundled: a standard type 30 clamp chamber is 2 in and a long-stroke type 30 is 2.5 in) and the 20%-of-brakes-defective out-of-service threshold of the CVSA out-of-service criteria, cited by name and not reproduced. At the limit counts as defective. The chamber manufacturer's limit, the criteria in full, and the inspector govern.

The comparison is arithmetic. The readjustment limit is entered by the user because it belongs to the specific chamber; no table of limits is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: readjustment_limit_in, measured_stroke_in, defective_brakes, total_brakes, margin_in, defective_fraction_pct

• At the limit is defective measured stroke AT the readjustment limit counts as defective, not only over itCVSA out-of-service criteria
• 20% rule a combination goes out of service when 20% or more of its brakes are defective; 2 of 10 is exactly 20%CVSA out-of-service criteria
• Limit is per chamber the readjustment limit belongs to the chamber type and size (type 30 clamp 2 in, long-stroke type 30 2.5 in), and is enteredchamber manufacturer data