Heavy Duty Trucking, September 2018

HDT SEPTEMBER 2018 32 WWW TRUCKINGINFO COM early 1600 vehicles were put out of service for brake violations during the Commercial Vehicle Safety Alliances unannounced Brake Safety Day in April On April 25 52 U S and Canadian jurisdictions conducted 11531 roadside inspections on commercial motor vehicles and 138 of the inspections ended in an out of service violation about the same as for a Brake Safety Day event held in September of last year Just weeks later law enforcement officials and brake safety experts were on hand at the CVSA Brake Safety Conference in Schaumburg Illinois offering detailed information on what officers look for during brake inspections plus tips to help drivers make sure their vehicle is ready to pass muster if it is selected for inspection Based on that meeting here are some refresher tips on inspecting your trucks air brakes Getting started Always check brake adjustments when brakes are cold Stroke measurements will be longer when brakes are hot due to heat expansion of the brake drum Your first inspection act is to identify the chambers and confirm their size based on the square inch area of the chamber diaphragm Brake chamber size can be determined by locating size markings engraved on both the clamp and body of the chamber If those markings are illegible you can also use a specially designed caliper to get the correct size measurement of the chamber Commercial vehicle brake chambers range in size from 6 to 36 with 30 the most common size in use Steer axle brakes are generally smaller ranging in sizes from 12 to 20 As a rule of thumb larger size chambers are typically used on heavier axles Once youve got the chamber size locked in you have to determine if youre dealing with standard or long stroke chambers This is important because the adjustment limit for a long stroke chamber can be as much as inch 13 mm longer than the stroke length on a standard chamber Long stroke chambers can be identified visually in three ways The airlines attach to a square shaped If you need a general idea as to whether your brakes are adjusted correctly and dont have time to carry out a full formed inspection you can measure the freestroke of a brake port on the brake chamber body Standard brake chambers have round airline ports A trapezoidal shaped tag placed under the clamp bolt that indicates the brake chambers maximum stroke dimension but not the brake adjustment limit Markings on the brake chamber body that indicate it is a long stroke chamber and only long stroke diaphragms are to By Jack Roberts Senior Editor jroberts@ truckinginfo com How to inspect truck air brakes Brake violations remain a common source of roadside citations and even crashes Heres a refresher course on the right way to make sure brakes are up to par SAFETY COMPLIANCE N PHOTO JIM PARK BRAKE ADJUSTMENT LIMITS CLAMP TYPE BRAKE CHAMBERS SIZE OF CHAMBER MARKING OUTSIDE DIAMETER ADJUSTMENT LIMIT MAX STROKE 6 None 4 1 2 115mm 1 1 4 32mm 1 3 4 45mm 9 None 5 1 4 133mm 1 3 8 35mm 1 7 8 48mm 12 None 5 11 16 144mm 1 3 8 35mm 1 7 8 48mm 16 None 6 3 8 162mm 1 3 4 45mm 2 1 4 57mm 16L L stamp on cover stroke tag 6 3 8 162mm 2 51mm 2 1 2 64mm 20 None 6 25 32 172mm 1 3 4 45mm 2 1 4 57mm 20L L stamp on cover stroke tag 6 25 32 172mm 2 51mm 2 1 2 64mm 24 None 7 7 32 183mm 1 3 4 45mm 2 1 2 64mm 24L L stamp on cover stroke tag 7 7 32 183mm 2 51mm 2 1 2 64mm 24LS Square ports tag cover marking 7 7 32 183mm 2 1 2 64mm 3 76mm 30 None 8 3 32 205mm 2 51mm 2 1 2 64mm 30LS Square ports tag cover marking 8 3 32 205mm 2 1 2 64mm 3 76mm 36 None 9 205mm 2 1 4 57mm 2 3 4 70mm SOURCE CVSA