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Safety systems
Page 57
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Bridgestone hopes to see the weight restriction relaxed, too. It has developed the M729 Greatec Mega Drive single driveaxle tyreand equipped it with a safety system named Aircept. If the tyre is punctured, causing a sudden loss of pressure, Aircept chambers inside the tyres, expand immediately, helping to support the load while the driver brings the truck to a halt.
Goodyear Dunlop's solution is to offer Duraseal, an extra belt built into the tread that's made up of a yellow, gel-like compound. The downside is that it increases the cost by around 10%, but if objects up to 6mm in diameter penetrate the tread, the compound flows into the puncture to create an airtight seal that prevents deflation so the truck remains mobile. If the object is removed the sealant flows into the hole that has been created. And the tyre can still be retreaded.
Punctures of this sort can occur repeatedly without the tyre having to be repaired and the sealant reapplied, according to Goodyear Dunlop. In a recent demonstration, a mixed-service truck tyre with Duraseal technology sustained 51 punctures without a loss of inflation," says a company spokesman.
The first manufacturer to offer Duraseal as an option is Renault. It is available on Omnitrac MSS steer and Omnitrac MSD drive-axle tyres for the Kerax.
And last November Goodyear Dunlop signed an agreement with Volvo covering the factory supply of tyres for Volvos and Renaults, but the deal is not exclusiveMichelin has one too.
On the face of it, sealants such as Duraseal would be ideal for single driveaxle tyres. But Continental's Roger Sanders has mixed feelings about their use, even though his own employer offers the Contiseal system. His concern is that repeated punctures, even if they are resealed, could potentially weaken the structure of the tyre, especially if they occur in the tread area closest to the shoulder.