Thread by @NorthHertsSam

I thought that I would take a short look at the tyre issues in the #AzerbaijanGP today as I've had a fair few questions about it already! (Thread)

Aston Martin were trying an alternate strategy with Lance Stroll during the race, starting on the (C3) hard tyre and running deep into the race, hoping for a safety car and to get track position as a result. It seemed to be going well, and then it wasn't.

The left rear tyre failed, with the inner sidewall separating from the rest of the tyre at high speed.

Stroll had done 29 laps on the tyre at that point, the longest stint of anyone, but well within the expected life of the C3 tyre (at least 40 laps) according to Pirelli's pre-race data.

Later in the race Max Verstappen suffered a similar failure on a Hard C3 tyre. His left rear tyre also failed on the straight and again the inner sidewall separated from the tyre. The tyre was also well within the expected life.

A few people have asked my why the failures happened on the straight and not in corners? The higher the speed the higher the load on the tyres, from both rotational forces and also downforce. So at over 300kph on the straight the tyre is dealing with a lot (or trying to at least)

There were no warning signs of either failure before they happened, though Pirelli does not yet know what the precise cause of the failures was. It is flying the tyres back to its HQ in Milan to study them.

During the race Pirelli looked at a number of hard tyres which had been removed from other cars (before the failure hit VER) and saw no issues.

However under the red flag Pirelli looked at the other hard (C3) tyres which came off the cars. They found a 60-70mm cut in the left rear tyre of Lewis Hamilton.

"It did not cut the construction, so the tyre was still in one piece, just the tread is cut, and when there was the red flag and Lewis came to the pit lane and changed the tyres we were able to find the cut” - says Pirelli.

"The cut clearly came from debris, because the tyre is clearly in one piece, and the cut it is clearly from the outside. In the case of Lewis, the cut was not deep enough to cut the construction, and in the case of Max and Lance there was an air loss and therefore a failure.”

The cut in Hamilton's tyre was clearly caused by debris says Medland

https://twitter.com/ChrisMedlandF1/status/1401641025723060229

But that cut could have come from Verstappen debris. May be unrelated to the issue seen with VER & STR.

"there was no warning or vibration detected prior to either incident, and the rear-left tyre is actually not the most stressed on this circuit. All of these considerations could point to an external factor."
Say Pirelli. "External factor" means debris in this context.

So Pirelli is suggesting that debris caused the failures, though its not yet clear where the three cars picked up the damage/debris. Or why only three cars showed this damage at quite different parts of the race. Identical failures from debris would be unusual but still possible.

For 2021 Pirelli introduced harder compound tyres as a direct response to the tyre failures at Silverstone in 2020. Those failures saw the sidewalls split from the front tyres.

Debris cut tyres caused failures at Silverstone (KVY) Mugello (STR) and at Imola in '21 (VER).

So for now it remains unclear exactly why the tyres failed, but cars running over debris and damaging the tyre is Pirelli's official theory.

There are only two other confirmed races where the C5, C4, C3 compound selection will be used, Russia & Abu Dhabi. Both quite different tracks to Baku, with nothing like the long full throttle section where the tyres failed. So its unlikely that this scenario will repeat.

I think thats all I have to say for now on the tyre issues, probably nothing to new in this thread, but I like writing these so I hope it was vaguely interesting!

I use F1 TV Pro to make these - its well worth signing up for: f1tv.formula1.com

@SimRacing604 @mikeev