Within existing Australian legislation, there are no regulations which prohibit the mixing of different tyre patterns, speed ratings or brands. The effects of mixing can be unpredictable and given that it would be impracticable to evaluate the infinite number of tyre combinations for each vehicle model, the following information is intended as a guide.
It is recommended that for optimum performance, cars and light vans should fit matching sets of tyres. Nevertheless, in general terms, the degree of tolerance to tyre mixing can be divided into two categories - those vehicles originally fitted with "T" rated tyres and lower, and those with "H" and above.
Vehicles originally fitted with "T" speed rated tyres or lower are less likely to suffer adverse changes in handling characteristics resulting from random mixing of patterns or major tyre brands. However, unless unavoidable, it is a sensible precaution to confine mixing to a minimum of matched axle sets.
Cars requiring H, V, W, Y or ZR speed rated tyres tend to be progressively less tolerant to tyre mixing as their performance increases. Generally, in these cases it is unlikely that adverse changes in handling characteristics would result from the mixing of patterns or major brands between axles (matched axle sets). Nevertheless, it is prudent to avoid mixing if possible and to use complete matching sets.
For certain high performance cars, matching sets of of vehicle manufacturer approved tyres are recommended to avoid compromising the handling characteristics of the car.
