Driving in the UK often means hitting the road on rainy days. What definitely helps to master the wet is a set of good car tyres designed for rain, simply called rain or wet weather tyres. Rain tyres, as the name suggests, can provide better performance on wet surfaces. Read on to find out what makes tyres perform better in the rain and how you can find the best rain tyres for your car.
What are rain tyres?
Car tyres basically fall under two main categories: summer and winter tyres. They are made with different road conditions and performance goals in mind, and that means they must differ in the composition of the compound used in the tyre construction, as well as their tread pattern types.
To put it simply, the concept of “rain tyres” applies to summer tyres with a special rubber composition which ensures excellent behaviour on wet surfaces. This includes the addition of filler particles, allowing the rubber compound to “fit in” better with the coarse areas of the road. It effectively increases the contact area between the tyre and the road surface, as the tyre ‘bites’ into the uneven sections with greater ease.
Climate and the selection of car tyres
Weather conditions are not always perfect for driving. The UK is well-known for its wet weather most of the year so you must think of driving in the rain when selecting new tyres for your car.
Sometimes, the rainfall is so profuse that the risk of aquaplaning rises, increasing the need for the right choice of tyre. In these situations, wet roads can often become a dangerous zone for drivers, as a wedge of water in front of the tyre can cause a loss of traction with the road surface, consequently causing a possible loss of control with the car.
Why are some tyres better on wet surfaces than others?
The success of rain tyres lies mostly in the use of an appropriate blend of elements. More active silica, for example, is a reliable compound and this is a common inclusion in the composition of Uniroyal tyres, which are well-known for good performance in the rain.
Similarly, the right tread pattern, or tyre surface, also helps. A directional V-shape, as seen on the likes of the Uniroyal RainSport 2, is optimal. The tread ribs on this pattern allow for an ideal distribution of tyre pressure on the surface - higher pressure builds up away from the tread centre. This allows water to be more effectively removed via the tread grooves.
While this occurs in directional tyres, this pattern is not always the best solution. Such a pattern is most optimal for tyres with a tread width of roughly 215 mm. In wider tyres, the distance water needs to cover, from under the front of the tread, is similar to that of asymmetrical tyres. However, rain tyres still typically feature a directional tread, due to its many other benefits.
Apart from having a symmetrical design, directional treads have minimally weaker traction, which is most noticeable when driving quickly through a bend. Asymmetrical tyres, on the other hand, feature outer tyre flanks that are closed. This is, of course, connected with each pattern’s ability to remove water.
Tread depth and water removal
With this in mind, let’s take a closer look at the depth of the tread pattern. The deeper it is, the larger volumes of water can be removed from underneath the tyre. Consequently, a deeper tread is better at reducing the risk of aquaplaning.
Source: MIRA (Motor Industry Research Association) report – ‘An Investigation into the Effects of Tyre Tread Depth on Wet Road Braking and Cornering Performance ‘ (MIRA-1002250)
The above graph shows how the braking distance changes on a wet and smooth concrete surface depending on the tread depth. At a depth of 6.7 mm, the braking distance is less than 29 m (from 50 mph to a complete stop). At 1.6 mm - the legal minimum allowed in the UK - it takes 42 m. The distance has increased by 44.6%.
That’s one of the reasons why it’s important to carry out regular tread inspections. While 1.6 mm is the legal minimum, we recommend fitting new tyres when the treads reach around 3 mm. This is also more critical in the winter, when the thicker treads are required to cope with snow, slush and other severe weather conditions.
All in all, car tyres with excellent water repulsion, a thick tread and a directional V-pattern matter most. Keeping this in mind, you can more easily determine if any given product has the qualities you need. If it does, there’s a good chance it could be the best rain tyre for you.