We have gone into the subject in detail with one of our engineers, young Stefano Orban, the Group Leader for Tyre Engineering, working within our Vehicle Performance Department. Stefano joined our team in 2018 as a Tyre Engineer, working on simulation development with tyre models, as well as working at the track.
- Stefano, we know what an important part the tyres play in the performance of a Formula 1 car and therefore how important is your work. Can you explain exactly what it involves?
The tyre is the only part of the car in contact with the ground and therefore it has to “manage” the longitudinal forces under acceleration and braking and the lateral ones in the corners. The tyre is one of the most complex components, made up of a variety of materials with characteristics that are usually not linear and depend on the combined interaction of many parameters. Scuderia AlphaTauri’s tyre group looks after all the development of simulation models and data analysis with the ultimate goal of optimising tyre use on track. The path to success in all this is very complex, covering simulation work on the computer, on the actual simulator and on track. However, with F1 testing limited to very few days before the start of the season, most of the car development, including tyre use, is done virtually through the use of models and potent number crunching tools. The physical behaviour of the tyres can be described in terms of mathematical formulae, hence the need to develop theoretical models for the tyres of varying complexity according to their final use. These models allow for extremely precise and accurate simulation of what will happen in the real world. This allows us to predict all the parameters that affect tyre behaviour, the temperature generated, the pressures, grip etc. so as to work out the best possible set-up of the car on track during the race, as well as during the design stage of the new car.
- Let’s talk about grip and temperature: how and when does a tyre perform at its best and how does that affect car performance?
Grip is strongly linked to temperature: the maximum potential that a tyre can transmit is tied to a specific temperature window. When we talk about temperature and grip, we mean the temperature of the various layers of tread. First there’s the outermost layer of the tyre in contact with the track, which is affected by surface temperature. From there it goes through to the innermost layer, effectively the carcass, which also determines the stiffness of the tyre. Grip is one of the key parameters for car performance. To give you an idea, a difference of one percent in grip at a classic track like Monza translates into about 0.3 seconds of lap time. We talk about the overheating zone, which is when the tyres are hotter than optimal and that leads to a sudden loss of grip, whereas a problem with warm-up is when the tyres are below the optimal temperature range.
- Let’s talk some more about the tyre-track relationship. We often hear talk of graining and blistering. Explain what that’s about.
Blistering and graining are two very different phenomena, but they are very similar in the way they limit performance, by causing a massive loss of grip. Blistering is caused by too high temperatures within the tread which causes some elements to dissolve and vaporise, which gives rise to the infamous blisters and craters on the tread surface. As for graining, that’s when small rubber marbles form on the surface, generally through a combination of cooler temperatures and high loads on the tread. In both situations, the tyre’s contact patch with the track is reduced which leads to a substantial loss of grip. Both these phenomena also lead to a rapid increase in tread wear, which therefore has a knock-on effect on race strategy.
- What’s the most demanding aspect of your job? When do you come under pressure from the team to find tyre performance?
One of the essential and possibly the most difficult parts of my job is the transfer to the track of everything we have learned from the simulation phase, effectively making sure that what you see in theory ends up being as close as possible to reality. Predicted tyre behaviour is also a key element. Being able to estimate extremely accurately all the parameters involved – for example temperatures, pressures, life and wear of the tread and the risk of graining or blistering – allows one to improve the car set-up and get the race strategy right. One aspect of this area is that development and reaction time to a problem is very much shorter compared to other areas and that encourages you to produce clear procedures relating to reaction time and problem management, to meet the needs of the whole team.
- How have Formula 1 tyres evolved in recent years and how will things change with next year’s wheel sizes?
Over the past few years we have gone from grooved tyres to slicks, then narrow tyres and the wide ones in 2017. Now we’re about to see the move from 13 inch to 18 inch as from next season. This challenge will be unusual, with tyres sizes pretty close to what we generally see on an average road car. The overall diameter of the tyre increases by about 10% compared to the current ones, while the construction and compounds will also be different. It’s not just the tyres that will go through a drastic change, but also related components such as the brake ducts that deflect air towards the rims,. Currently these are made to different configurations depending on how much air is to be channelled towards the rims. This will not be possible as from 2022, because there will only be one configuration for all tracks, whatever the weather. Such a drastic rule change is always a very high level technical challenge as the margins for car development are much bigger than one usually gets from one year to the next. So using prediction models and gaining an understanding of the new tyres is of paramount importance. That is based on a very limited amount of experimental data from the models that must be calibrated before being used in the world of virtual simulation.
- Each track has unique characteristics: the type of asphalt, ambient temperature, sand, lateral loads… how do you go about learning a track?
Each track has its own energy level determined by its configuration and that will have a key impact on generating temperature in the tyres, as well as on the level and the profile of wear on the tread. We use track data in our simulation tools at the computer and in the simulator to estimate the impact that the parameters in play will have on the vehicle dynamics. We also look at the effect of a change in the atmospheric conditions, the track and air temperature on tyre behaviour. Different track surfaces can have different levels of abrasiveness, that can range from the size of the chippings of which it is made, which means we are looking at macro roughness, right through to microscopic abrasiveness not visible to the naked eye. We use a laser scanner to measure abrasiveness at all the circuits and we use the data gathered from our calculation models.
- Does the driving style of the drivers in any season influence your work and your decisions?
Driving style is a key parameter. Aggressive driving, which involves locking the brakes or getting plenty of wheelspin, will generate considerably higher temperatures that can limit performance and even cause irreversible structural damage, requiring a pit stop or even retirement in the worst case scenario. Driving style has an effect on the total amount of energy that a tyre has to handle and it also affects tread wear and degradation in terms of performance. It’s a key part of the Tyre Engineer’s role to give the driver and his race engineer, the information and suggestions as to driving style and the tyre management strategy, so that they are in the right temperature window and that they meet their target in terms of degradation and wear.
- Tell us about a recurring nightmare and dream you might have: what is the biggest nightmare for a tyre engineer? Graining, blistering, incorrect pressures, unexpectedly high temperatures? And what about a recurring dream: a totally predictable compound, a driver who does not destroy his tyres, a robust tyre and that’s it?
Graining and blistering are always a nightmare for a tyre engineer, as they cause car performance to drop off a cliff. That can turn into an opportunity at times when you can limit its severity or keep it at bay for a while. If you can do this, while also doing a better job than your opponents, you can finish the race in a better position. Unfortunately, or possibly fortunately, the idea of a tyre that is 100% predictable is a utopian ideal. By definition, tyre behaviour can tell you everything and nothing. The same test, carried out several times in controlled conditions can produce quite different results, because of the nature of the tyre, its complexity and non-linear behaviour. At first sight, this might seem frustrating and unsatisfactory, but actually it means that the work of a tyre engineer is always fascinating with new methodologies, mathematical models and new testing technologies developing and progressing all the time.