Retread or replace? Working it out on cost per kilometre

Retread or new is decided on cost per kilometre, not on purchase price. Divide what the tyre costs you by the kilometres it delivers, subtract the value of the casing you get back at the end, and compare the two pence-per-kilometre figures. A premium new tyre at twice the price of a retread is cheaper if it runs more than twice as far and leaves a casing worth retreading.

That is the whole method. The rest of this guide is about using reliable operating data.

Price divided by kilometres is the base. Four other things move the answer, and three of them usually favour the more expensive tyre.

• Casing value at removal. A tyre that comes off as a retreadable casing has a residual value. A tyre that comes off as scrap has a disposal cost. That swing is real money and it belongs on the ledger of whichever tyre earned it.
• Fuel. Rolling resistance differences between tyre classes are large enough on a trunking vehicle to outweigh the whole price difference. On urban stop-start work they matter far less.
• Downtime and roadside cost. One motorway call-out, with the vehicle stood and a customer’s delivery late, buries the saving on a set. This is why casing quality is not an abstract virtue.
• Removal depth. A tyre pulled at 4 mm to protect the casing has delivered fewer kilometres than one run to the legal limit, but it has delivered a casing. Count both.

Feed the two options into the cost per kilometre calculator with the kilometre figures your own removals actually show, not the manufacturer’s expectation. A fleet that measures removals has a decisive advantage over one that argues about invoice prices.

An all-steel truck casing is an asset with a second life in it, and often a third. Treated as scrap it is worth nothing and costs money to remove. Treated as stock it offsets a meaningful share of the replacement cost.

Casing management means knowing which casing came off which vehicle, at what depth, in what condition, and where it went. In practice that is: pull tyres at a set removal depth rather than at failure, inspect at removal rather than at the retreader, keep casings dry and out of sunlight, and track the rejection rate. A fleet whose casings are being rejected at the retread plant has a maintenance problem somewhere upstream, and the rejection rate is the cheapest diagnostic available.

Retreaders also apply an age limit to casings, and the limit varies between plants and between markets. Agree it with yours before you build a policy around it rather than assuming a number.

A good casing has an intact belt package with no separation, sound sidewalls with no cord damage, undamaged beads, no heat history, and no repairs beyond what the retreader accepts. Maintenance and handling affect whether a casing can be reused.

• Running flat or seriously under-inflated. The single biggest casing killer. Sidewall flex generates heat, heat breaks down the rubber-to-steel bond, and the damage is internal and invisible. A tyre run flat for a short distance is finished as a casing even if it looks fine and holds air afterwards. This is also the mechanism behind zipper failures during inflation, which is why a run-flat tyre is inspected in a cage or not at all.
• Repeated under-inflation. Slower version of the same thing. Twenty per cent low for weeks does not blow the tyre out; it cooks the casing quietly and shows up as a rejection months later.
• Sidewall cuts and kerbing. Once the cut reaches cord, the casing is scrap. Urban delivery and yard work destroy more casings this way than tread wear ever will.
• Impact breaks. Potholes and kerb strikes at speed pinch the casing between the object and the rim flange. The break is often only visible from the inside.
• Bad repairs. External string plugs, unpatched punctures, oversized repairs and repairs in the shoulder or sidewall will all be rejected. A correctly done two-piece repair from the inside, within the retreader’s size limits, generally will not be.
• Regrooving into the belt. Only on tyres marked REGROOVABLE, only to the maker’s template. Cut too deep and an asset becomes scrap in ten seconds — see reading the sidewall.

Pre-cure, sometimes called cold cure, bonds an already-vulcanised tread strip to the buffed casing with a layer of cushion gum, curing the bond in an autoclave at a relatively low temperature. The original sidewall and its markings survive, tooling costs are low so pattern choice is wide, and the casing sees less heat. Mould-cure, or hot cure, applies uncured rubber to the casing and cures it in a rigid mould, producing a new tread and new sidewall surface — the tyre looks like a new tyre, and the shoulder and sidewall are renewed rather than left as found.

Both processes are capable of excellent results and both are capable of poor ones. In service, the plant’s inspection discipline and the quality of the casing going into it matter more than which process it uses. Consider the retreader’s inspection and quality controls alongside the curing process.

Trailer: yes. This is the classic retread position and for most fleets it is uncontroversial. High static loads, moderate speeds, no traction or steering demand, and the axle where scrub and kerb damage make an expensive new tyre hard to justify.

Drive: it depends on the work. On regional and trunking work a good retread drive tyre earns its place. Where traction is critical — tipper and mixer work, site access, winter gradients — the tread compound and pattern of a purpose-built new drive tyre is usually worth the difference, and the casings coming off that work are the ones most likely to be damaged anyway.

Steer: generally not. The steer axle is the one where a failure is a control event rather than an inconvenience, and it carries the vehicle’s highest single-tyre loads in single fitment. Many fleets prohibit retreads on the steer axle as policy, and a good number of customer and PSV contracts require it. Check the operator’s own policy and any contract terms before fitting, and where a bus or coach is involved, check the operator’s engineering standard as well.

Retreads are entirely legal on commercial vehicles in the UK. What the law is concerned with is that a retread is made to a recognised standard and is identifiable as what it is.

The principle to work to has three parts. First, the retread must have been produced to a recognised standard or approval — historically the British Standard BS AU 144 for retreaded tyres, with commercial vehicle retreads now normally produced under the relevant UNECE approval for retreading. Second, the finished tyre must be marked so that it can be identified as a retread and traced to the retreader, with the size and service description it is approved for as retreaded. Third, once fitted, a retread is held to exactly the same in-service standards as any other tyre: tread depth, condition, load and speed rating for the axle.

An unmarked retread is the problem case. If the tyre cannot demonstrate what it was made to, nobody can show it complies. Confirm the current standard and approval references with your retreader and with DVSA guidance before writing them into a specification document — the numbering has changed over the years and current guidance should be used.