Heavy Duty Trucking, March 2020

BRAKE MAINTENANCE is discovered In order to maintain proper balance a better strategy albeit costlier is to assure both axle sides are treated and repaired equally even when one side seems OK Brake balance is often overlooked because it is often manifested in unequal brake lining wear between the tractor and the trailer Because the tractor and trailer are rarely or never serviced together lining thickness inconsistencies remain unseen When axle lining thickness inconsistencies are evident from measuring the brake lining wear patterns brake imbalance is likely the cause This condition should immediately be addressed as one or more axles on one side of the truck or trailer is doing more braking work than the other possibly creating an unsafe condition The performance of braking systems is only as strong as its component parts The well being of drivers and the motoring public depends on each fleets braking system maintenance and inspection proficiency These proficiencies should extend all the way to the last line of defense the driver One last note Brakes do not stop trucks tires stop trucks Without well maintained tires the most robust braking system will be compromised Bob Stanton is a career fleet manager having spent 18 years in the private sector and 26 years in the public sector Today he operates his own fleet consulting firm based in Cumming Georgia Just as up to date training is essential in educating technicians on the latest PM processes the same is true for drivers Reinforcing the importance of a high quality pre trip inspection through training can be money and time well spent Unfortunately this step is often missed by fleets who prefer to presume their drivers are performing this task as thoroughly now as when they were testing for their commercial drivers license Proactive fleets conduct driver inspection workshops on a regular basis which includes the process of testing and adjusting brakes on tractors and trailers Unless drivers have specifically been trained under FMCSR 39625 they are prohibited from adjusting their brakes Fleets that train to this requirement recognize both the operational and safety benefits But again drivers should not be trying to adjust automatic slack adjusters Dont overlook brake imbalance Yet another brake system element that is often overlooked is balance In a tractortrailer application balance may be critical in brake operation Brake imbalance can result in a degradation of safety by compromising brake system performance If the combination braking system is mistimed or out of balance stopping distance may be greatly extended In a single truck or tractor application certain maintenance strategies include repairing brakes only on one side of the axle when an issue to apply the brakes allowing the technician or the driver to conduct a walk around to listen for air leaks and visually inspect tubing and connections for bulges or looseness Another use for this seemingly primitive tool is to check for wheel end play or wobble after removed wheels are reinstalled following the performance of brake or related wheel end maintenance such as lining bearing or seal replacement On the other end of the sophistication scale for brake inspection tools some state inspectors and fleets use a Performance Based Brake Tester PBBT in their inspection and or maintenance processes This tool includes the loaded weight of the vehicle per axle and calculates the effectiveness of the trucks actual braking performance under load While being a generally accurate test it also can pinpoint specific axles with braking system issues allowing focus on that axle specifically The drivers role It is an industry given that commercial drivers are required to perform a pre trip inspection But it is also an industry given that a typical drivers pre trip inspection is less comprehensive than most fleets would prefer and or admit Although the pre trip inspection is the first line of defense in preventing an inspection related out of service violation many drivers perform this function in a sub standard fashion and fleets suffer the consequences AIR DISC BRAKE MAINTENANCE I operated a fleet of 135 trailers equipped with air disc brakes in the late 1970s They were truly unique then With the proliferation of air discs on tractors and trailers today however any article on brakes cannot ignore them Air disc brakes are designed to be easily inspected and repaired Their only true complication A thorough inspection cannot be performed with the wheels on Using a mirror and a flashlight a cursory wheels on visual inspection can be performed routinely Its relatively simple as there are only few items to inspect at each axle end Technicians or drivers can visually inspect the brake chamber and hoses for structural integrity leaks or cracks There are no lube points to hit Using a flashlight and mirror the end caps covering the guides should be present The three wear indicators the hash marks on the casings the chamfer areas on both sides of the rotor and the thicknesses of the pads can all be visually inspected A wheels off inspection should include both the visual inspection above as well as a forced physical horizontal and lateral movement of the brake assembly to confirm the free travel of the components This can be performed by hand no tools are required In addition to their simplicity because air discs have no slack adjusters there is little chance of an inspector placing an air discequipped vehicle out of service for a brakerelated issue PHOTO WABCO A technician uses feeler gauges to measure the pad to rotor clearance on a Wabco Maxxus air disc brake to ensure the brake caliper is functioning properly HDT MARCH 2020 62 WWW TRUCKINGINFO COM