Case to answer 06 January 2014

Tyres make a big impact on fuel economy and maintenance bills. Stretching the life of rubber is the aim of the new ContiLifeCycle plant in Hannover, as Ian Norwell discovers

Most fleet engineers send their used cases away for retreading, but where do they go? And how efficient is the process? The truth is, third party providers may be feeling the pinch as tyre manufacturers increasingly take the task in house in an effort to improve control and offer a product that's as good as new.

Continental is no exception. Indeed, the manufacturer has just opened a combined hot and cold retreading plant in Hannover-Stöcken, which claims a world first, by being a rubber recycling operation to boot. So good is its green card that it is supported by local government, and for fleet operators there's the quality guarantee that comes from an integrated process.

Raising the image of the retread is long overdue in the opinion of Herbert Mensching, Continental's managing director for commercial vehicle tyres. "The detailed inspection that a used case gets before it is taken to produce a retread, and the re-manufacturing process it goes through, make it as good as a new tyre," he insists.
And his message is probably now getting across even to owner-drivers dedicated to bling and truckfests, despite increases in horsepower and braking performance requirements.

Either way, the opening of Continental's Hannover plant signals the end of a role for its third party provider. As from next spring, all Conti retreads will be supplied from Stöcken. Conti stresses that it's not an observation on the quality to date: it's about economies of scale and pooling expertise.

That said, the Stöcken plant will recycle 4,000 tonnes of reclaimed rubber and produce 180,000 retreaded tyres annually. Further, as well as pulling tyre remanufacturing in house, Continental has expanded its facilities at Hannover with a €15 million investment, including a new R&D centre. And the firm is also pushing the limits of rubber recycling technology.

Rubber from used tyres is notoriously difficult to recycle efficiently. Apart from the steel cord that must be separated, vulcanisation puts a large proportion of the rubber beyond retrieval. "We introduced conventional recycling in serial production in 2009, but we felt there were opportunities for increasing the 3% [recycling] that was then possible," states Dr Boris Mergell, head of product development for truck tyres. That sounds like a low figure, but it's a battle with the mechanics of locked-in rubber and chemistry.

"In launching the ContiLifeCycle plant, we have doubled that figure," states Mergell, adding that the improvement is largely due to using a devulcanising agent, lower temperatures and reduced shear forces. That must be regarded as a result not just for the economics of recycling, but the environment, too. Fleets keen to be green, may take note. Whether it is Euro 6 engines or a retreaded tyre that uses double the recycled rubber, it all helps to change the grubby image of truck fleets.

Different European markets have different attitudes to hot or cold retreaded tyres. Europe is evenly split, with 51% taking cold retreads and 49% going for the hot option in 2012. The UK is over 60% biased towards hot and Germany almost the opposite. Whatever your preference, Mensching says that retreads should be a vital part of cost efficiency for fleets, through casing management, buy-back and exchange, supported by a reliable identity tracking database.

"In terms of mileage, reliability, fuel efficiency and comfort, a retread offers a full performance as a second life tyre. It's not a compromise," claims Mensching. "The direct cost of tyres is around 5% for a transport operation, but they influence up to 45% of costs, with fuel economy by far the biggest. When a fleet operator sees the same performance from a retread as from his new tyres, it makes him think." Conti claims a retread can offer a 22% saving over new tyre costs.

Production process
The retreading process feels very like that of a new tyre production line. Initial shearography inspection is more comprehensive than X-rays, and is followed by electronic speckle pattern shearing interferometry, to check cases for defects.

Significant repairs can be accommodated. A nail puncture in the face of the tread can be safely repaired by drilling and filling, which ensures that no corrosion remains in the steel cord.

The overall process – from inspection to casing buffing, repair, tread application, curing and final inspection – is impressive. Shaking off an outdated reputation may be difficult, but the image of the retread as a poor relation is due for recycling itself.

Ian Norwell

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