Tire Wear on Set Back vs Set Forward Steer Axles
Posted by dolan from cookeville, TN, US on January 29, 2008
Werun trucks with set back ster axles and set foward axles, the set back axle truck wears tire out faster that the forwards do. We run the same tire on both. Can you tell me why this happens?
I forwarded your question to Mike Beckett, President of MD Alignment. Mike knows more about tire wear than anyone I know.
"First you get a more effective transfer of loads to the steer axle with a set back vs a normal axle set. This does not mean more than about 500 lbs per tire in load but it is a more consistent transfer and this will have some minor effect. The larger effect is the turning angle on set back front axles. Most set forward axles turn 20 to 25 degrees as compared to 30 to 50 degrees on set back axles.
This increase in steering angle increases the "ackerman" effect on Toe when the vehicle in in a turn. A sharper steering angle and more toe on turns causes the vehicle to turn shorter circles and therefore it is more maneuverable but it does this at the expense of tire life. In my experience, on line haul trucks the net difference in tire life is about 10 to 15% between the two.
If you want to change this, adjust the steering stops on the axle to reduce turning angle and see how much you save. Just remember that the truck will require larger areas to turn around."
