A tyre which has been designed to operate equally well in either direction will inevitably be compromised in terms of ultimate performance. Directional tyres, however have been designed to rotate in one direction only, so performance - wet grip, directional stability and handling - can be optimised.
Obviously the tyre must be correctly fitted and rotate in the direction indicated on the sidewall!
An asymmetric tyre gains its’ performance advantage through having different tread patterns on its’ inner and outer sides.
Typically, the tread pattern on the inner side of an asymmetric tyre will have more grooves to aid water dispersal and improve grip on wet roads. The outer side will have a larger plain surface area to increase grip and stability during high speed cornering on dry roads.
As with directional tyres it is very important to ensure that the tyre is fitted ‘the right way round’.
Should it be necessary in an emergency to use an incorrectly fitted directional or asymmetric tyre (following a puncture for example) you must treat the tyre as a ‘temporary spare,’ drive at a reduced speed and have the tyre correctly refitted as soon as possible.