At this point in the year, when rain lurks day in and day out, the tire becomes even more important as a safety element when traveling. But, do we really know what the characteristics of a tire are when it comes to driving on wet surfaces? Development engineers at Bridgestone’s Rome Technical Center (TCE) answer the big questions this raises.
Firstly, a good tire, to offer optimal wet rolling, must have high compound grip, efficient water drainage capacity and good rigidity of the tread blocks and ribs. Thus, the design of the tread pattern is the protagonist of the water drainage capacity. The more rubber that can be put in contact with the asphalt, the more the grip of the compound and the rigidity of the blocks are used. He secret is in the balance between the volume of grooves that allow water evacuation and the rubber in contact with the ground, in short, an optimized contact surface.
The compound, for example, is a key element due to the combination of two phenomena: adhesion and hysteresis. Adhesion arises from intermolecular bonds between the rubber and the road surface. Hysteresis represents the loss of energy in the rubber as it deforms as it slides on the road surface. Likewise, the casing plays a minor role in wet braking. In the case of lateral grip, the greater the rigidity of the carcass, the less the deformation of the contact surface with the ground. Less deformation of the contact print means a greater ability of the pattern to maintain contact with the surface.
As a general conclusion, a greater width means a larger contact surface and greater braking potential. In dry conditions this is always valid. In the rain, the characteristics of the car (for example, weight, tire pressure, etc.) and the condition of the road surface have a lot of influence.
Tire height also plays a minor role in wet braking. And it is about achieving a balanced combination between the characteristics of the compound, the tread design and the casing material, so that the tire offers a progressive evolution of grip while driving, without sudden reactions.
Finally, at a compound level, wet performance does not directly affect the useful life of the tire. However, trying to reduce rolling resistance does directly affect the useful life of the tire.