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F1 cars can literally boil the rubber in their tyres. 

It’s called blistering, and what is interesting is that it tells a much bigger story about the pressures Pirelli are under to create tyres that aren’t as good as they could be. 

Despite the extensive research and development, the tyres are the only component of an F1 car, that isn’t at the limit of what is physically possible.

So we’re going to break down the incredible engineering that goes into these tyres, and how going a bit too fast for 5 laps, can completely destroy them. 

To understand this, we need to look at the first step in this story – how the tyre is constructed, which is incredibly interesting.

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Back to how tyres are made.

In road cars, tyres are most often made with steel bands within a rubber compound. However, the steel is heavy and wouldn’t withstand the incredible forces F1 cars produce. 

So F1 tyres use a combination of kevlar, nylon and polyester to create a strong structure that supports the tyre. This combination allows the tyres to withstand 3 tonnes of sideways loading, over a tonne of downforce as well as shock forces from the road and curbs. 

Next, this structure is impregnated with a mix that we call the tyre compound. It’s mainly synthetic and natural rubber with other things like Carbon Black which gives the tyre its colour and improves the tyres life. 

It makes up the sidewall, the carcass and the tread around the outside of the tyre. 

There are also other ingredients that are used to manage how the tyre reacts to heat, preserves its life and how it releases from the mould.

This is then cured in a mould, that creates the shape and strength of the tyre. 

The heat and pressure cause the rubber to poly-merise into longer chains, taking shorter rubber molecules and forming them into longer ones, this gives the tyre it’s elastic quality to absorb bumps and conform to the track.

It’s the compound that is the interesting thing here because those who know F1 will understand that Pirelli have a very tough job to do. 

They have to create 5 different compounds, from hardest to softest that all wear at different rates and provide varying levels of grip – all to create interesting racing on a Sunday. 

They do this by tweaking the compounds, where the softer compounds create more grip but wear out much faster – and the harder compounds offer less grip, but can last many more laps. 

But have you ever questioned why this is? Why are softer tyres faster? Why do they wear quicker? 

It comes down to how the tyre creates friction, if we zoom in close on the contact patch – you can see that the rubber is soft enough to fit into the small crevices in the road. 

This means that when cornering, braking or accelerating, the force is put into the road by all these small pieces of rubber. 

But as you can imagine, when you put 1000 horsepower through this soft rubber, or brake from 200mph, it can shear off in the road surface. 

And you can see this happening during a grand prix, with all the marbles off the racing line.

You can reduce this wear with a harder compound, not only because the rubber is harder and less likely to shear off, but because it doesn’t fit so deep into the road surface. Also explaining why you get less grip. 

This difference can be massive, where using the hard compound can cost you a second a lap – but also meaning you can go triple the distance of a soft compound tyre. 

F1 tyres have only 3mm of usable tread, so if you wear through this, all that’s left is the carcass – the structure of the tyre – which provides very little grip. And this has happened numerous times over the years. 

But you can also kill your tyres with temperature. You will hear this referred to from the race engineers as Thermal Degradation, or simply “deg”.

As you can imagine, putting these incredible forces through the rubber – the constant stretching and releasing of the rubber creates incredible heat – and if you create any wheelspin or lock a brake this effect is further increased. 

The tyres have a temperature ‘window’ where they create the most grip and last the longest, below this – the tyre is too cool and can create graining – I’ll explain that later. 

Above this, you risk creating so much heat that the rubber boils and creates these blisters. 

This blistering can be caused by high track temperatures, too much air pressure in the tyre or just pushing too hard. 

All of these things lead to very high temperatures through the core of the tyre, which melts the rubber deep in the tyre, and can cause huge lumps of rubber to break away. 

And as you can imagine, removing these huge lumps of rubber can dramatically reduce grip.

But all of this seems a little strange – the tyres in your road car are able to work in anything from -20ºC up to 120ºC. So why do these F1 tyres produce such extreme reactions to small variations in temperature?

Well, it comes down to the fact that Pirelli made them to behave this way because it creates more exciting strategies and better racing. Tyres with shorter life mean for more pit-stops, different strategies and so more overtaking.

But the teams have come up with a few clever ways to protect their tyres, anything from pre-wearing tyres, clever mechanical design or the drivers using different driving styles. 

Firstly, they test the tyres extensively to understand how they behave at different pressures, temperatures and track conditions. Small differences in track temperature can cause massive differences in how the tyre wears. 

For instance, in Bahrain where the track temperature tends to be high, and the track surface is rough. The degradation on the tyre can be massive, so this leads to many teams not using the Soft tyre – despite it being the fastest. 

This was purely because, at the start of the race, fully-fueled cars on a hot track would overheat the tyres within 10 laps or so – leading to most of the teams preferring the Medium tyre for the race.

Another trick is using a scrubbed set of tyres. This is where the teams will do a couple of laps on a set of tyres to wear them slightly and put them through a heat cycle. They do this in a practice session so the tyres are pre-worn for the race.  

But surely if the tyres degrade so fast, why would you wear them down before the race? You may think, it doesn’t really make sense. 

This is interesting, and it works because of the chemical make-up of the compound. You will have seen in Imola last week, Mercedes fitted worn Mediums to Hamilton’s car, despite having a spare fresh set available. 

This heat cycle in the scrubbing process cures the rubber slightly, it can actually cause the tyre to become slightly harder – potentially lasting longer.

It also removes the shiny outer surface of the tyre, which can be very slippery, especially in wet conditions. 

It’s more common in other race series where the release agent used to get the tyre out of the mould, can get into the rubber of the tyre – so wearing this away can improve grip. 

It will only make a small difference, but it’s those marginal gains that are so important in F1. 

But going back to the temperature window, why do you also get issues when the tyres are cold?

As we explained earlier, higher temperatures cause the rubber to soften up – so cold tyres are slightly harder. Why does this cause an issue?

The issue here is graining, this looks like a darker patch on the tyre where the rubber is graining and then falling away – and it’s extremely detrimental to performance. 

It happens when the tyre is being worked hard before it’s up to the perfect temperature. We often see this at street circuits where tyre warmup can be trickier with the slightly lower average speeds. 

It’s just like using an eraser, where the rubber tears away. This adds a layer of loose rubber between the tyre and the track, which reduces grip, causing more sliding and even more graining. 

One way around this is to carefully warm up the rubber on the out lap before pushing too hard. 

Another way is to use the brake temperatures to heat the tyres. We made a whole video on this, but simply – the brakes can get up to 1000ºC in the race and are cooled by air from the brake ducts. 

This hot exhaust air can be used to heat the tyre, through the rims – bringing the core temperatures up and preventing graining. This is why you see these fins on the wheels, they increase the surface area and so radiate more heat into the tyres. 

But one of the best tools to control the tyres, are simply the temperature sensors on the car that constantly monitor them. This goes not only to the teams but also onto the driver’s dash. 

The drivers will be very aware of what the ideal temperatures are for qualifying, starting the race and normal running. 

But the majority of the feedback the driver gets is in the feel of the car, and just by looking at the tyre. Of course, they will used to how a tyre should look and feel through a race. 

Showing the incredible skill to be managing these tyres whilst also fighting wheel to wheel with other racers. 

Again, thanks very much to Squarespace for sponsoring this video – you can check them out with the link in the description or use code Driver61 to get 10% off your first purchase. 

Be sure to check out this video that fully explains how Mercedes manage the heat in their tyres by using a genius wheel design. 

Thanks very much for watching and I will catch you in the next one. 

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