How to Extend Casing Life on a Truck Fleet

A truck tire has two parts that age at different rates. The tread is consumed by the road, and it is meant to be. The casing is the steel and rubber structure under it, and a casing that has been looked after can carry more than one tread over its working life.

That gap is the whole economic case for retreading. A fleet that buys a new tire every time the tread wears out is paying for a new casing each time, whether the old one was finished or not. A fleet that keeps its casings sound only pays for tread on the second and later lives.

The question a fleet manager is really answering, then, is not "how long do our tires last?" but "how many treads do our casings carry?" The habits below move that number.

Heat is what breaks a casing down from the inside, and under-inflation is what makes the heat. A tire running low flexes more with every revolution, and the flexing builds temperature in the sidewalls and belts where nobody can see it.

The damage is cumulative and quiet. A casing that has run low for months can look fine on the outside and fail inspection for internal separation when it finally comes off.

What works in practice:

• Check pressures cold, before the unit moves, against the specification for that position and load.
• Use one calibrated gauge per yard rather than whatever is in the cab, so readings mean the same thing across shifts.
• Treat a tire that keeps losing air as a problem to find, not a chore to repeat. A slow leak that gets topped up every morning spends its afternoons underinflated.
• Pay attention to duals. A low tire beside a correctly inflated partner carries less load and scrubs, and its partner carries more than its share.

Tread is the casing's protection. Once it is worn through to the belts, every stone and pothole goes straight into the structure. A tire run to the last few miles of its tread often comes off with damage that makes the casing unusable, which means those last miles cost the price of a casing.

Most fleets that retread set a pull point: a tread depth at which a tire comes off for retreading rather than staying on to wear out. The right figure depends on position, application and the casings you run, and it is worth agreeing with your store rather than picking one from memory. What matters is having a number, writing it down, and measuring against it at inspections.

A pull point only works if someone measures. Tread depth belongs on the same inspection sheet as pressure.

This is the single habit with the clearest effect on scrap rates. A tire that loses its air and keeps rolling under load is usually destroyed within a short distance, casing included. The driver who limps to the next exit to get somewhere convenient has, in most cases, turned a retreadable casing into rubber for disposal.

Make the rule plain to every driver: when a tire fails, stop where it is safe to stop, and call. Purcell runs 24-hour roadside assistance at 48 locations, and the article on emergency tire service covers the first minutes of a failure in more detail.

It also helps to tell the technician whether the tire was driven on after it went down. That information belongs with the casing when it is assessed.

A casing waiting for collection can deteriorate faster in a corner of the yard than it did on the truck. Three things do most of the harm:

• Sunlight. Ultraviolet light ages rubber at the surface.
• Standing water. A casing lying in water, or stacked so it collects water inside, invites corrosion of the steel and moisture where it does not belong.
• Ozone sources. Welders, electric motors and generators produce it, and rubber stored near them ages faster.

Keep pulled casings indoors or covered, off the ground, away from electrical equipment, and gathered in one place so collection is a single pickup rather than a search.

A casing that arrives with a note of its unit, position and service history can be assessed with more context than one that arrives anonymous. Over time those notes also show a fleet which positions and which tire lines give the most retreadable casings, and which keep failing inspection.

Purcell collects casings at 54 locations and retreads them at seven plants, including the plant in Potosi, Missouri at the company's founding address. A record that travels with the casing is useful at every step of that route.

The companion article on which retread casings pass inspection covers what the inspection looks for and why some casings do not make it.

• Cold pressure checked against specification, with a calibrated gauge.
• Tread depth measured against the fleet's pull point.
• Any tire that keeps losing air written up and fixed.
• Drivers briefed: when a tire fails, stop and call.
• Pulled casings stored dry, covered and off the ground.
• Each pulled casing marked with unit and position.

Fleets running a program through fleet services can build these checks into scheduled visits rather than relying on memory between them.