Hidden Tire Costs in Vehicles with three or more axles

If you are operating vehicles with three or more axles, you might have hidden costs caused by excessive tire wear

In case of two axle vehicle, the misalignment of the rear axle moves the thrust angle aside of the centerline of the vehicle which do change the drivability and tire wear will be somewhat higher, but not that significantly. BUT when you add third axle or fourth axle, the game changes dramatically. The yaw angle cannot be freely changed, as the misaligned axles or individual wheels are starting to fight each other, resulting accelerated tire wear and even tire blowouts.

In a case of large fleet, the tire wear rate is an important indirect indicator about the wheel alignment errors. Automatic tire wear monitoring will help to get the information without additional work.

In our customer’s bus fleet with 50 three axle buses, seven excessive tire wear problems were found. In the worst example, the tire lifetime at third axle left hand wheel was only 1.5 to 2 months. After some maintenance history investigation, it was found that 13 additional tires were spent during last two years.

Picture: The diameter chance of the third axle left hand wheel (Rear 2 Left) indicates excessive wear rate. The wearing starts again after the tire replacements

The older history did not include the reason for the tire change, was it due to low tread depth or failure, but the at least two latest tire replacements had a clear pattern. Tire replacement, excessive wear to low thread depth, puncture, tire replacement, excessive wear to low thread depth, puncture, and so on..

At the first thought the bus with lot of punctures might look just unlucky one, but that’s not really the case. When the tire wears fast it also gets hot and while hot, the tire is prone to punctures, especially when the tread depth is low.

Now when the tire wear rates are seen from the automated system, all the seven buses will be inspected to avoid excessive maintenance and fuel costs. Both will also lead to more sustainable bus fleet operation.

Kimmo Erkkilä, E3 Innovations Oy