Shocks wear slowly over time and varies dependent upon operating environment. Worn shocks are defined as those that have lost over half their dampening performance, allowing for excessive wheel hop, permitting up to 4 times greater tire load variance. Average Life of Truck Shocks are 150,000 miles for Steer and 225,000 miles for rear.
The ATA-Truck Maintenance Council findings (RP643) reports that “Fleets have found it beneficial to install new shock absorbers when installing new tires, to maximize tire life.”
*U.S. Department of Transportation and OECD – DEVINE analysis of Modern Truck Air Suspension found that once the shock worn past 50% dampening performance, road wear damage increased by over 20% as a result of increased air-ride tire load variance creating a jack-hammer type effect between the tire and pavement, in turn severely reducing tire life as well.
*SAE Study 962152 “Worn Shocks contribute to wheel hop and or greater tire load variance x4 = (+/- 80%)”, the primary effect of which is scalloped tires. Worn shocks are defined as those that have loss over half their dampening performance.
*TMC RP#643 recommends that shocks be replaced on regular maintenance schedule, preferably at the same time tires are replaced. (See Industry Study Link)