The November issue of the German 'Caravaning' magazine includes a feature article on a comparison test to determine if towcar tyre equipment has any measurable effect on stability of an outfit. The result may be interesting to readers of this forum so here's a short summary:
Test car: VW Passat Estate 2.0TDI
Tyre equipment (base condition): Michelin Primacy HP 205/55R16 on 6.5Jx16 wheels
Tyre equipment, modified for comparison test: Michelin Primacy HP 235/55R17 on 7.5Jx17 wheels
Caravan: BÅrstner single axle 1800kg MTPLM, loaded to 1600kg and with noseweight adjusted for the purposes of the test to 15kg (no typo error!) Caravan fitted with a Winterhoff WS3000 stabiliser.
Result:
Critical speed of outfit with the standard tyre equipment: 84km/h (52mph)
Critical speed of same outfit with low profile tyres: 92km/h (57mph)
The critical speed is the maximum speed from which an outfit will recover from a snake on its own without any intervention by the driver or by electronic means (where fitted).
Conclusion:
As can be seen from the results, the low profile tyres, although not that much wider than the standard ones, raised the critical speed by 5mph. Hence, wider low profile tyres certainly do have the opportunity to improve stability and that further improvements could be achieved by deviating from the standard tyre equipment even more than in this test.
What the article does not mention, however, is whether the same improvement would also be achieved on a wet road surface.
Test car: VW Passat Estate 2.0TDI
Tyre equipment (base condition): Michelin Primacy HP 205/55R16 on 6.5Jx16 wheels
Tyre equipment, modified for comparison test: Michelin Primacy HP 235/55R17 on 7.5Jx17 wheels
Caravan: BÅrstner single axle 1800kg MTPLM, loaded to 1600kg and with noseweight adjusted for the purposes of the test to 15kg (no typo error!) Caravan fitted with a Winterhoff WS3000 stabiliser.
Result:
Critical speed of outfit with the standard tyre equipment: 84km/h (52mph)
Critical speed of same outfit with low profile tyres: 92km/h (57mph)
The critical speed is the maximum speed from which an outfit will recover from a snake on its own without any intervention by the driver or by electronic means (where fitted).
Conclusion:
As can be seen from the results, the low profile tyres, although not that much wider than the standard ones, raised the critical speed by 5mph. Hence, wider low profile tyres certainly do have the opportunity to improve stability and that further improvements could be achieved by deviating from the standard tyre equipment even more than in this test.
What the article does not mention, however, is whether the same improvement would also be achieved on a wet road surface.