Fast-Running Resistance of Retreaded Tyres
At present, nearly 15 percent of the roughly 600,000 tons of old tyres accruing every year are retreaded. Retreading actively contributes toward ecological conservation by sparing resources. Whereas about 35 litres of crude oil are needed to manufacture one new tyre, this requirement is lowered to about 5.5 litres for a retreaded tyre.
On its Interior Drum Testing Facility, the Federal Highway Research Institute determines the types of quality assurance necessary and viable for retreading processes. Tyres undergo two different tests: A test according to ECE regulation 30 and an independent, special test.
In the ECE test, the tyre is run for 20 minutes at the maximum speed and wheel load permissible for its class. The internal pressure of the selected tyre is set to 2.8 bar. In the special test, the tyre is run for 24 minutes, also at full load and full speed. To reflect real conditions, however, the tyre pressure in this case is lowered to 1.7 bar or 1.9 bar, depending on the chosen type.
Burst test tyre
After 180 ECE test runs, about 20 percent of the tyres failed. 25 percent of the remaining tyres failed during the special test. The obtained results also indicate that a speed limit of 210 km/h is advisable for retreaded tyres. German retreading companies voluntarily opt for a lower classification at high speeds. The age limit of six years for recyclable carcasses is appropriate and viable.