Uniroyal’s RainExpert Delivers Improved Safety & Wear

Over the years, Uniroyal has developed a strength in the area of wet weather tyres, so it is hardly then surprising that its latest product has been named the RainExpert. The new range for super-mini, compact and medium cars covers 78 sizes between 13 and 16-inches – some 96.5 per cent of the European compact and high performance segment. The first 43 sizes were released in January, and a May launch is planned for the remaining 35 sizes.

Uniroyal reports improved performance compared with its ‘Rallye’ tyre: up to five per cent more resistance to aquaplaning, as much as a three per cent reduction in braking distances, and five per cent more mileage performance. The tread on the RainExpert, comments tyre engineer Jürgen Brockmann, has a hydrodynamic tread featuring a directionally orientated and consistent V-shaped pattern. A three or four groove version is used depending on the tyre’s size. In wet weather, the tread pattern’s circumferential grooves are designed to quickly take up the water and efficiently disperse it to the sides of the tyre via channels between the tread segments.

“Even the grooves themselves have a double concave shape”, explains Brockmann. “This prevents any swirling of water which would counteract the effect of rapid water dispersion.” Depending on the tyre’s width and speed, and the depth of water on the road, a rain tyre needs to shift up to 42 litres of water per second to maintain contact: “This is where the V-shaped tread pattern helps because it is better than a non-directional pattern at expelling the water in the right direction away from the contact patch”, he adds.

Wet braking performance of the new RainExpert is improved over that of its predecessor, reports Uniroyal, through the use of using ‘special’ sipes instead of standard sipes. These sipes increase tread stiffness during braking, leading to shorter wet-braking distances. Extra safety also comes from the tyre’s more stable tread elements in the shoulder region. They serve to improve handling and assist the driver in critical steering manoeuvres.

As previously mentioned, the RainExpert’s mileage has been improved over its predecessor. “Abrasive tyre wear is low and evenly distributed thanks to the RainExpert’s well-balanced tread stiffness”, explains Brockmann. “This adds up to a long tyre life and, consequently, more economical and resource-conserving driving.”

Three millimetres – this is the summer tyre wear limit frequently recommended by tyre safety organisations, the limit at which water drainage rapidly deteriorates, the risk of aquaplaning increases significantly, and braking distances become longer, above all on wet roads. “So we decided to give the new RainExpert a system of tread wear indicators to warn drivers once that limit has been reached”, explains Lukas Kosmala, product manager at Uniroyal. “Small bars with a height of three millimetres have been placed between the individual tread elements. The tyre’s wear limit has been reached once the bars are at an even level with the surrounding tread.” A raindrop on the tyre shoulder indicates where these S-TWIs (summer tread wear indicators) are located. The bars run across the grooves in a line with the raindrop.

Another feature in extending the life of the tyre is the VAI or visual alignment indicator on the tread. VAIs are umbrella symbols vulcanised into the tyre and serving as visual identification of a vehicle’s misalignment. “Wheel alignment is precise if the VAIs are worn down evenly on both sides of the tread. If the indicators are worn down to different degrees, wheel alignment should be checked to prevent uneven tyre wear”, advises Kosmala.