Tyre wear and degradation
As a set of tyres does more laps, it gets slower. That loss of performance is called degradation, usually shortened to "deg". How quickly it happens at a given track, and which cars suffer most from it, decides how many pit stops a race needs and often who wins.
Wear and degradation are different things
People use the words loosely, but engineers separate them.
Wear is the rubber physically being used up. The tread gets thinner each lap until there's little left.
Degradation is the drop in lap time. A tyre can lose a lot of pace while still having plenty of rubber on it, usually because it's been overheated. This is called thermal degradation, and in modern F1 it's the bigger problem of the two. Drivers often pit with tyres that still look healthy because they've stopped gripping.
Graining
Graining happens when the tyre slides across the track surface and small strips of rubber tear and then stick back onto the tread. It leaves the surface lumpy, so less rubber is in proper contact with the road and grip drops.
It's most common when the tyres are too cold for the track, for example early in a stint on a cool day. Graining can clear up if the driver is patient and the rough layer wears away, after which the tyre may come back to life. Teams sometimes wait it out rather than pit.
Blistering
Blistering is caused by too much heat. The inside of the tyre gets so hot that pockets form under the surface and pieces of rubber break away, leaving holes in the tread. Unlike graining, it doesn't get better. A blistered tyre usually needs changing.
Flat spots
If a driver locks a wheel under braking, the tyre stops turning and slides along the track, scrubbing away rubber in one place. That leaves a flat spot. The tyre is no longer round, so it vibrates heavily at speed. A bad flat spot can shake the suspension and the driver's vision enough that the team will call them in, even if the rest of the tyre is fine.
The cliff
Tyres don't always fade gradually. Sometimes they keep a steady pace for many laps and then lose a lot of time very suddenly, a second or more in a lap or two. This is called falling off the cliff. It usually happens when the tread is almost worn through or the tyre has overheated past the point of recovery.
The cliff is why teams are careful about extending a stint. A driver who stays out two laps too long can lose far more time than they would have spent in the pits.
Marbles
Rubber worn from tyres collects as small balls, called marbles, just off the racing line. Driving over them is like driving on ball bearings. It's one reason overtaking can be hard late in a race: the driver going around the outside of a corner may find their line covered in marbles. Drivers also pick marbles up on their own tyres, which is why you'll see them weaving on the slow-down lap after the flag.
What affects degradation
Deg changes from track to track and from car to car:
- The track surface. A rough, abrasive surface wears tyres quickly. A smooth one is gentler.
- Corners. Long, fast corners load the tyres for a long time and heat them up. Tracks with lots of heavy braking and hard acceleration are harder on the rear tyres.
- Temperature. A hot track surface makes overheating more likely.
- The car. Some cars are naturally kinder to their tyres. A car that slides more will overheat them faster.
- The driver. Smooth inputs and careful use of the throttle can add laps to a stint. See tyre and energy management.
When tyres fail
Pirelli designs tyres to lose grip long before they become unsafe, but failures still happen, usually after debris causes a cut or a tyre is pushed far beyond its expected life. At Silverstone in 2020 several cars suffered front-left failures in the final laps, and Lewis Hamilton crossed the line to win with a deflated tyre.
When a tyre fails, Pirelli and the FIA investigate. If they find the problem is with the tyre rather than debris, they may raise the minimum pressure or limit stint lengths at later races.
Reading degradation from the outside
You can spot high deg on the timing screen by watching lap times rise steadily through a stint, then drop sharply after a pit stop. On the timing screen the tyre age column shows how many laps each set has done, which helps you judge who's likely to stop next. And if you'd like to see it as a chart, the dashboards on this site have a tyre degradation panel that plots it for every driver.