Taking tires seriously

Jun 2018

Vehicle Technology

An important aspect of road safety regarding commercial vehicles is the regular maintenance and care of tires. Tires that burst – particularly on the front axle of semi-trailer tractors and trucks – can result in sudden instability and, in turn, skidding, potentially resulting in very severe accidents. But people traveling behind vehicles on which a tire has burst are also at risk due to the tire remnants that have come loose and are lying on the carriageway.

Tires need to be set to the correct pressure in order to function correctly. The statistical assessment of damage to commercial tires by DEKRA has shown for a number of decades now that a large proportion of tire failures can be attributed to a lack of care including insufficient tire pressure or excessive load. Even where the cause cannot be clearly determined, reduced air pressure is involved in a high number of cases. “Cannot be clearly determined” means that, in these cases, multiple overlapping factors have led to tire failure.

Existing damage to the tire in the tread areas, however, which does not lead to an immediate loss of filling pressure, also presents a problem because moisture penetrates up to the steel belt via the channel of damage, causing the belt to corrode and reducing the level of adhesion between the steel cord and rubber. This can result in the protector suddenly detaching from the tire body together with parts of the belt; in these cases, the tire may also burst. Drivers and workshop personnel should therefore check the filling pressure of all tires on a regular basis, adjust the pressure where necessary and check the tires for damage. The gradual loss of filling pressure in particular can be detected at an early stage by a tire pressure monitoring system.

When deciding which tires to fit on a vehicle, you have to take into account the transport tasks that the vehicle will undertake. Low-section tires certainly offer the advantage of enabling a higher transport volume; however, these dimensions are disadvantageous when it comes to load-bearing capacity. A front axle of a vehicle with tire dimensions of 385/65 R 22.5 for a semi-trailer tractor can bear 3.3 tons, for example, which is almost 50 percent more than tires with dimensions of 295/60 R 22.5. A drive axle equipped with low-section tires with dimensions of 315/45 R 22.5 (dual tires) can bear 11.6 tons, which is significantly less than the load-bearing capacity of 13.4 metric tons offered by tires with dimensions of 315/70 R 22.5. A three-axle trailer equipped with 445/45 R 19.5 tires can bear around three metric tons less compared with when 385/65 R 22.5 tires are fitted. Using the wrong tires for a particular vehicle configuration can result in damage, even if the tires are filled to the correct pressure level.

The process of fitting low-section tires – especially in combination with a tire pressure monitoring system – can present another challenge. Highly skilled personnel are essential for fitting tires correctly and without causing damage. Trade associations BRV (Bundesverband Reifenhandel und Vulkaniseurhandwerk – German tire retailer and vulcanization trade association) and wdk (Wirtschaftsverband der deutschen Kautschukindustrie – association of the German rubber industry) have therefore published fitting instructions in collaboration with DEKRA.

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