The problem nobody feels
A driver notices a tractor pulling. A trailer out of alignment produces almost no feedback at the wheel. It runs slightly crabbed down the road, scrubbing rubber off its own tires and pulling at the tractor's drives, and the first symptom is usually a tire bill nobody can account for.
That is what makes this service easy to skip and expensive to keep skipping.
What goes wrong
- Axle alignment to the centerline. An axle sitting out of square makes the trailer track at an angle to the direction of travel.
- Axle to axle alignment on a tandem or tri-axle, where one axle fights the other.
- Kingpin to axle alignment, which sets how the whole trailer follows the tractor.
- Damage. Curb strikes, dock impacts, overloading, and simple age in a hard-working trailer.
How to spot it
- Trailer tires wearing on one side, or one axle wearing faster than another.
- The trailer visibly tracking off to one side when you watch it follow the tractor.
- Drive tires on the tractor wearing in a pattern that alignment of the tractor alone does not explain.
- Trailer tires being replaced noticeably more often than the rest of the fleet's.
Align the unit, not the vehicle
The useful principle here: a tractor and a trailer are one system. Aligning the tractor while ignoring a trailer that tracks crooked fixes half the problem and leaves the half that is harder to see.
Where a fleet runs trailers that swap between tractors, which is most fleets, a crooked trailer spreads its wear around the whole fleet rather than staying with one unit. Finding it means looking at the trailers rather than the trucks.
See heavy-duty truck alignment, offered at 40 Purcell locations, and fleet services for scheduling both together.
What it protects
- Trailer tire life, which is the direct saving.
- Tractor drive tire life, which is the one people miss.
- Casings, since irregular wear can cost a casing its retread life. See retreading.
- Fuel, because a crabbed trailer is a trailer being dragged slightly sideways for every loaded mile.
What to tell the store
- The trailer type and axle configuration.
- The wear pattern, by axle and by side.
- Whether the trailer has been hit, overloaded, or had axle work.
- Whether the tractor is being aligned at the same time, which is usually the sensible order.