Fuel figures are the evidence nobody reads
Fleets collect fuel data and use it to compare drivers. The same data will identify a crooked trailer, and almost nobody uses it that way.
The reason it works is that a trailer out of line is being dragged slightly sideways for every mile, and that costs fuel continuously and predictably. It does not vary with weather, traffic or mood the way driver behavior does. It is simply always there.
The thing to look for is therefore not a bad figure. It is a figure that changed and stayed changed, on the same route with the same loads, with no other explanation. That pattern points at something mechanical, and on a combination the trailer is the end nobody checks.
For a fleet that swaps trailers, the comparison is even more useful: if the poor figures follow a particular trailer rather than a particular tractor, you have found it without measuring anything.
What gets measured
Axle alignment to the kingpin, the relationship between axles on a tandem or tri-axle, and the condition of the suspension and mounting hardware.
Heavy-duty truck alignment is offered at the same store, so the combination can be measured rather than one end of it.
Confirming it on the tires
Once the fuel data has pointed at a trailer, the tires will confirm it. Look across each axle rather than at one tire: a trailer out of line wears opposing edges on the two sides, which is a pattern you only see by comparing left against right.
The other confirmation costs nothing. Have somebody follow the combination on a straight road and look at whether the trailer sits squarely behind the tractor or slightly to one side.
Winter adds a reason
A trailer that is already being dragged sideways is using grip it may want on a slick surface, and a trailer that steps out is harder to recover than one that stays in line.
That is an argument for doing the measuring before the season rather than after it, alongside everything else on the winter list.
About this store
The Loveland store carries trailer tires and every other Purcell category, opens at 7:00 AM, and is managed by Joe Servin. Denver and Colorado Springs also align trailers.
See the national trailer alignment page for all 36 locations.