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The same or different?

Serhii Maslov Section: Winter tyres Updated:

Do you have to fit matching tyres on different axles?

Ukraine’s traffic regulations require matching tyres on one axle, without specifying drive type or season. For a two-wheel-drive car this rule can still, in some sense, be followed in real life, though you do need to understand that different tyres (meaning the tread pattern and its state, that is, the tread depth) have different braking characteristics, which will inevitably change the distribution of braking force across the axles the car maker calculated for, especially under emergency braking. How will that show up in terms of safety? Most likely, in most cases, hardly at all (especially where the tyres’ basic characteristics are similar), but nonetheless the likelihood of a skid does still increase.

The situation with four-wheel-drive cars is completely the opposite. On a four-wheel-drive car in winter, all the tyres must be the same! The same pattern (model) and the same tread condition (depth, wear). Do not forget that in a four-wheel-drive car all four wheels are constantly working hard, not just in corners and under braking. So upsetting the balance of driving force at each wheel that the car’s design intended, on a slippery road, can lead to some very sorry consequences, even in the most seemingly harmless situation.

More on this topic

Asymmetric treadAn asymmetric winter tyre is a good alternative to a classic winter tyre, possibly even with improved figures, although a lot here depends on the specific model and maker. What is rubber hardness on the Shore scale?Hardness and stiffness are different things, and greater hardness and stiffness are not always good or even needed for every condition. High-speed winter tyre, or “European winter”Many makers now produce high-speed winter tyres. As a rule they have a high speed rating and a strongly “sporty” tread pattern. Where do people usually buy part-worn tyres?Buying tyres from someone you know is certainly safer, because you are more likely to find out the truth (or at least part of it) about the tyres’ past. How do you choose tyre width for the season?In reality, all else being equal, tyre width only affects one parameter: the size of the tyre’s contact patch with the road surface. What does that mean? Classic winter tyresA classic winter tread. Everything here is moderate. Medium lateral gaps, wide longitudinal grooves, classic tread block height: 7-8 mm. A tyre like this can be either directional or not.

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Tyre testsOften the main argument for choosing a particular tyre becomes the place it won in some “independent” test - how justified is that?