As far as the tires support?

Motorhomes are not featherweights - the test vehicles in the current ADAC test have a permissible total weight of 3.5 tons. The demands on the load-bearing capacity of the tires are correspondingly demanding.
In the tested mobile homes, however, this load-bearing capacity was not sufficient. The Renault Master and Ford Transit have practically reached their tire load limit at 99 and 97 percent, respectively. The VW Crafter even significantly exceeds the permissible tire load capacity on the front axle - the cause here, however, is the manufacturer´s incorrect air pressure information. Even the Mercedes Sprinter doesn´t exactly shine with large reserves in terms of the load capacity of the tires (92%). Only the Peugeot Boxer remains just under 90 percent load, conclusion: In almost all test vehicles, the stress on the tires is unacceptably high. All of them lack a safety cushion, as is common in cars.

Weak point valve

The valves are an additional weak point in motorhome tires. Tire valves in a simple rubber design are standard in mid-range cars and are completely sufficient there. In the case of mobile homes, however, they show clear safety deficits. This can result in sudden loss of air and destruction of the tire. However, three of the five motorhomes tested were equipped with these inadequate rubber valves. Only the Peugeot Boxer and the Ford Transit had steel reinforced valves:

* According to the vehicle manufacturer, the tire pressure of these vehicles may be up to approx. 5 bar, in practice even higher values ​​are to be found. According to the standard, rubber valves of this type may only be used up to a tire pressure of 4.5 bar.

* When driving, especially at speeds above 110 km / h, there is also the effect that the rubber valve bends strongly outwards in the direction of the wheel circumference under the influence of centrifugal forces, up to a Apply to the rim flange. The sealing of the valve base in the rim is no longer guaranteed, which can result in rapid escape of air.

* Motorhome rims are often exposed to high temperatures when braking. These contribute to the aging (embrittlement) of the rubber valves. You can play it safe with valves from the so-called 600 series. These are massive valves for pressures up to approx. 7 bar or - as the best solution - metal valves.

Expert advice is available from the tire dealer, who can also determine at a glance which version is currently installed on the motorhome. If the worst comes to the worst: have the valves replaced.


Copyright ADAC:
ADAC motorhome chassis tested in 2006


,wr,, 2009-03-04