A trailer parked loaded is still being worked
Seasonal operations park trailers with weight on them. A grain trailer that does not get emptied right away, a float with a machine left on it between jobs, a trailer loaded and ready for a run that keeps getting pushed back.
Nothing is moving, so nobody counts it as use. The suspension is holding that load the whole time, the springs are compressed, and the tires are carrying weight at one spot on their circumference for weeks.
Two consequences follow. Suspension components that spend long periods under load settle differently from ones that cycle, which over seasons contributes to a trailer sitting and tracking differently from how it left the factory. The tires also develop flat areas, which usually recover and sometimes do not if the period was long enough and the pressure low enough.
What that means practically
Empty a trailer if it is going to stand, where the work allows it. It is free and it removes the whole issue.
Where it has to stand loaded, check the pressures before it moves rather than after. A tire that has been flat-spotted and is also under-inflated is the one that fails on the first road run of the season.
Measure the trailers that stand loaded most. If a fleet has one that is always the parked one, that is where to start.
What gets measured
Axle alignment to the kingpin or coupling, the relationship between axles on a tandem, and the condition of the suspension and mounting hardware. The national trailer alignment page covers the signs worth looking for.
Heavy-duty truck alignment is at the same store, so a combination can be measured rather than one end of it.
About this store
The Jonesboro store carries trailer tires and every other Purcell category, opens at 7:00 AM, and is managed by Tony Kuehnel.
See the national trailer alignment page for all 36 locations.