In modern F1 cars, tires play a massive role in how fast drivers can push on a circuit. The health and compound of tires greatly affects where drivers end up in the race. Fans must have heard the words 'graining' and 'blistering' when F1 engineers, team principals, and drivers talked about tires. These phenomena essentially explain different kinds of tire degradation as the cars race around the track.
Over the years, F1 tires have developed quite a lot and are technological marvels. The chemistry and engineering involved in creating different rubber compounds for different conditions is extremely complex and advanced.
What is graining in F1?
Graining is a phenomenon where small tears and ridges form on the tire surface. This happens when the smooth surface of the tire wears off as it rubs on the tarmac. This causes the rubber compound to heat up and tear, resulting in small ridges or ripples on the tire surface.
When parts of the tire begin to tear, it gradually starts to pull out of the surface and then fuses back into the tire. Hence, these ripples begin to create a grainy pattern on the tire surface.
This phenomenon usually occurs when an F1 car decelerates or takes a corner, since the friction between the tire and the road increases quite a lot. This varies from car to car, however, since each team sets their suspensions and tire pressures differently. It also depends on whether the car oversteers or understeers.
When the tire starts to grain, the car loses grip since the overall surface area of the tire decreases due to uneven tire surface. Drivers still manage to work the grained tires as some of the excess rubber starts to wear off and create another layer of a smoother surface. This workaround, however, is quite hard and they usually pit for new tires.
What is blistering in F1?
Blistering is another phenomenon where small chunks of tire rubber break away from the main surface of the tire. This happens when the internal temperature of the tire increases, loosening the rubber compound on the surface and allowing bits of rubber to completely break off.
This is much different than graining since chunks of rubber completely detach from the tire and don't fuse back in to create an uneven layer.
Hence, blistered tires lose a lot of grip since several parts of rubber are not even on them. It is much more dangerous than graining as it affects the overall integrity of the tire. If the blistering continues, it can result in a tire blowout which may cause crashes.
Blistering can occur at any part of the track since it is related to the internal temperature of the tire. It mainly occurs when the tire compound cannot handle the amount of downforce created by the F1 car, or when the track temperature is too hot. The internal temperature and stress can also increase due to stiff suspension as the tire acts as a shock absorber and takes up a lot of vibrations.