Tech Briefs: Tyres, Or How Evolution Brings Revolution In WorldSBK

In the era of control tyres in WorldSBK Pirelli has shown that it’s no excuse to halt development

In racing, you’re always competing. You’re battling against the clock and you’re battling against your rivals. Performance and pushing the boundaries is the key to success. But what happens when you are a control supplier to a championship? For over fifteen years that’s been the conundrum for Pirelli.

It’s very easy to look at tyres in a control era and think that development has stood still. Why would a tyre company want to push to the limits when the only time they’ll be noticed is if something goes wrong? For Pirelli, the sole tyre supplier to WorldSBK since 2004, the goal is to ensure development keeps pace with the evolution of current road-going machinery.

A control tyre doesn’t have to mean a lack of development. Recent years have shown the opposite, with changes to the profiles of tyres and the introduction of a host of “development” tyres in 2019. The goal for Pirelli for these tyres is to develop them into the tyres that customers can buy in the shops for use on track days and in club races. The goal for Pirelli has always been to produce production tyres from their involvement in WorldSBK for their customers.

Confidence

In terms of racing the goal for teams and riders is always the same: performance and confidence. Whether you’re using a control tyre or the type of tailor-made rubber that was used in MotoGP fifteen years ago, riders are always looking for the same things. They want a front end that gives them the kind of good feeling that breeds confidence. The front should be stiff enough in the braking zone to maintain its form and shape, but also supple enough to absorb bumps.

Feedback is the most important thing for a rider from the front end, while the rear is all about being able to open the throttle with confidence when the bike is leaned over. The tyre needs to give good grip to let the rider open the throttle when their leaned over at 60 degrees. With forces of over 1.3G moving through the rear tyre as a bike accelerates, being able to trust the rubber is key. Otherwise the result can be very painful.

Knowing how the front and rear tyre has to perform is important for a manufacturer, but they also have to be durable during a race. In the early stages of a race a tyre offers its best potential performance. Grip is theoretically at its maximum and the rider can push harder as a result. This is why riders use fresh tyres in qualifying or when they’re looking for a fast lap in practice. With a full fuel load this can be masked in the early laps, but the potential of a tyre is at its maximum at this point.

Managing tyres

The window of opportunity for a rider is crucial. The goal is to keep performance as stable as possible throughout the race because as a race progresses the tyre will inevitably start to drop off and performance will decrease. Top riders are able to manage for as long as possible and understand how not to push a tyre too hard, too soon during a race and overuse it.

The goal is to finish a race as fast as possible, and that’s usually achieved by not overstressing the rubber. If you can keep the window of performance open for longer during a race it will pay off in spades at the end.

For Pirelli the goal is to provide a tyre that allows them to do this, but which will also usable for an ordinary member of the general public on a trackday. It’s a difficult balancing act, and when you’re producing prototype tyres it’s a lot easier to aim for performances that will only last 100km. Knowing that customers will buy the tyres seen in WorldSBK means that tyres are developed with the goal of great performance for any road-going Superbike.

A control tyre should mean that it’s easier for a manufacturer. They can stay out of the limelight and bask in their tyres being used to win world championships. Instead, having a control tyre actually present opportunities to develop your product. These are the best Superbike riders on the planet so you might as well use them to test different things.

Getting the allocation right

The WorldSBK regulations define that riders have just 11 front tyres and 13 rear tyres available over a weekend. This means that it’s crucial to use your allocation wisely. As a result Pirelli have spent the last number of years introducing lots of different tyres in recent years. These have been with different profiles, compounds and constructions to provide tyres that have very different operating windows for their performance.

Some tyres work better in cooler conditions, others are good for circuits that place heavy demand on tyres. Variety is the spice of life for Pirelli in WorldSBK, where the demands of Phillip Island, Misano and Qatar are all very different.

The front tyres on offer from Pirelli in recent years have been fairly stable but the rear tyre has seen lots of development. Since the introduction of a larger profile rear tyre in 2018, which also necessitated a corresponding increased profile front tyre, Pirelli has brought forward lots of newly developed tyres.

Development path

The easiest way to chart the development of tyres for Pirelli is to look at their tyre allocation for races over the last year. There have been nine different “race” compound rear tyres introduced that should eventually be seen on sale at dealers. The switch to the larger profile tyres was made to take advantage of the power of a current Superbike.

In addition to developing these race tyres, Pirelli also introduced tyres specifically for the regulations defined by WorldSBK. Pirelli introduced a new SCX tyre for the ten-lap Tissot Superpole race, and two different qualifying tyres have been developed for the Superpole sessions. That’s a lot of development for a championship with a “control” tyre.

To see a company invest time and money into manufacturing this amount of rubber that will eventually be made available for the general public to buy is impressive. The change in tyre profile has had a big impact on racing. For some, Michael van der Mark for instance, the larger profile suited their size and style of riding and allowed them to manage a tyre easier.

The change was introduced in 2018 and the Dutchman, one of the taller riders on the grid, was one of the first riders to make the switch. His Donington Park double in 2018 hinged on being able to adapt to the new tyres. With more weight to move he’ll always exert more from a tyre than a lighter rider. The newer tyres levelled the playing field for him.

Tyres for tracks

Tyre wear is always key in racing and managing a tyre throughout a race takes skill. At some race tracks - Phillip Island for instance - the forces being put through a tyre are huge. During this year's races we saw riders coming through Turn 3 with smoke pouring from the rear tyre. With long, black lines being left behind them, it was obvious they were laying down rubber. How much? Over 1kg per tyre.

Team’s can manage this by using a range of sensors. The key information is pressure and temperature. Internal sensors will monitor the tyre pressure and temperature while an external infrared sensor is used to manage the rear tyre temperature. At circuits like Phillip Island this is absolutely crucial, and keeping this temperature as low as possible is key.

During the pre-event test, Alex Lowes was constantly adapting his bike and style to ensure that he managed his rear tyre temperature. This paid off in spades on the race weekend, Lowes victorious in Race 2 and leaving Australia leading the championship. To manage his tyre wear he was less aggressive through the likes of Turn 3, and even though the racing was frantic, he was able to stick to his plan. His tyre management throughout the race was the difference between him and his Kawasaki teammate, Jonathan Rea, when they came to the flag. For some riders, the difference in riding style and physical traits can equate to a difference of 10°C in tyre temperate, and that can be the difference between winning and losing.

Looking ahead

After a race you’ll see riders and engineers huddled together to debrief. They want to find ways to improve ahead of the next outing. Tyre manufactures are the same. All used rubber in WorldSBK is sent back to Pirelli’s Italian factory and inspected. This inspection takes two forms; visual and technical.

The visual inspection is simple; does the tyre look like it’s done it’s job correctly? Is it wearing in the correct places? If not, it will be put through a more rigorous process where the structural integrity will be tested and then the compounds that go into the tyre are also checked.

As a tyre wears, layers of the construction are removed. A tyre is constructed by a process of baking the rubber layer by layer. As one layer is removed, section by section, the tyre changes. Pirelli need to assess this to understand how their tyre is reacting during a race.

A team also needs to understand this. They need to understand how best to use their tyres throughout the course of a weekend where they have a limited number of tyres available to them. With 11 front tyres and 13 rear tyres available a team needs to plan out their weekends. With practice sessions, a Superpole session and three races there’s a lot to think about. Will you use a SCX tyre in the Superpole Race of will you will you use a harder compound? Maybe the allocation over the course of a race weekend will force teams to use a tyre in practice that would be unsuitable for a race. You need to be able to understand your weekend programme before the start of the weekend to fully understand how you’ll split your allocation.

The decisions will typically come down to the rider’s crew chief. The engineer will decide what tyres work well for a bike and what compounds will be needed for a race weekend. Pirelli will tailor their allocation based on the track temperature, layout and abrasive nature of the asphalt. At a typical race weekend teams will have two front tyres available and three rears, in addition to the Qualifying tyre and Superpole Race tyre. From round to round the compounds might change but the permutations don’t; you need to find the best use of your allocation for your weekend.


Pata Yamaha WorldSBK Crew Chief Phil Marron: How a team manages their tyres over a race weekend

In the WorldSBK regulations we’re allowed to use 24 tyres per weekend. We can have 11 front tyres and 13 rears. Before the bike leaves the box we must apply a label/sticker to the tyres and this is what you see the person checking at the end of pitlane during a session.

During the course of a weekend we will debrief with the Pirelli engineer on Thursday morning. Based on the information shared from Pirelli we will decide on our allocation of compounds. We need to see the quantity of compounds to fit for Friday.

At some tracks Pirelli will have more options available than others. We will have some new options and some that aren’t new. We’ll have some that have been tested in the Italian championship and some have never been on track before. It’s important to use the Thursday debrief to understand the options available.

All of the options presented by Pirelli need to be considered. It’s very important to work as a team too, and to fast-track our understanding of the tyres it’s important to share the workload between both riders.

Phillip Island is such a unique track on the WorldSBK calendar. There is an incredible strain on the left side of the rear tyre and Pirelli supply us with options that we won’t use at any other circuit and that’s also why its not good to use Australia as an example to describe a normal game plan for a race weekend.

Our normal objective is to identify the tyre with the best performance. We do this in terms of outright pace but also the consistency we can get from the tyre. Different bikes work in different ways with different riders and that’s why the SCX rear tyre, which is designed for the ten lap Superpole race, has been used by some riders in the full length races!

In FP1 we typically use the soft front tyre, the SC1 tyre, to let the rider get reacquainted with the speed. We’ll use the harder rear tyre (SC1 rear) of the options to clean the track. This can also sometimes allow us to save a preferred option for later if the quantities are low. We will put two exits on these tyres, and for the third exit we’ll use a new front and rear (the softer SC0 Rear) and see how the bike behaves with the increase in grip offered from the softer rear.

In the FP2 session, if the bike setting is close to being acceptable our is aim to start with a new tyre on the front and rear with the option that we predict will be the race choice. The goal is to put two thirds distance on those tyres if possible, In the second exit of the session we will try the SCX. Firstly, we’ll evaluate if it has any advantage over the race options and secondly if it can last for the ten-lap duration of the Superpole Race.

Saturday morning starts with the FP3 session but it’s only 20 minutes and normally is very early in the morning with cold track conditions. It’s generally difficult to draw any conclusions on tyre performance in this session.

With the Superpole now a 25-minute session again we can get some information from the start by using the SCX tyre and then switching to the Q-tyre. We’ll pair that with a new front tyre. The Q-tyre changed to make it more durable, and at some tracks that means you can actually make two laps with it. We always try to allow enough time for that. With the session finished we should have two remaining SCX rear tyres from our allocation for the Superpole Race on Sunday morning.

For Race 1 on Saturday afternoon we will have one set of tyres ready for the race, but we’ll also plan for a red flag and have a back-up set ready. At some tracks we might even have a second back-up set.

The Sunday Warm-Up session can sometimes require us to use the front tyre we used in Superpole with the Q-tyre, depending on the allocation for the weekend and what our preferred choice of front tyre is. The goal is always to have enough of your preferred tyre for the races. In the ten-lap Superpole Race, if the conditions are similar to the previous sessions when we used SCX tyre, we will have it ready. In this short race the SC0 rear tyre is also a very good option. For Race 2 we will be prepared with the same quantities as race 1.


The rules

Regulation 2.4.7 Tyres

a) The maximum number of tyres, of any type, available to each rider during the event will be 24 (11 front tyres – 13 rear tyres).

b) A maximum of 15 tyres can be mounted per rider at any time.

c) The maximum number of each type or option of tyre is according to the “allocation list” at each event. This is event specific and supplied to teams by the official tyre supplier. It is the same for every rider in the class. Tyre types may not be exchanged between riders. The official tyre supplier will ensure that each rider’s allocation limits are adhered to.

d) With the consultancy of the SBK Technical Director and the official tyre supplier only Race Direction may alter the “allocation list” during an event.


Tyre usage

What affects tyre wear? Weight, power, and riding style.

What does a tyre need? A front tyre needs to give feel and breed confidence for the rider. It does this by being stiff enough in braking to maintain its form and shape, but also supple enough to absorb bumps. Feedback is the most important thing for a rider, and in WorldSBK you see this with many riders opting for a harder compound front tyre so that it’s stiff in the braking zone. For the rear tyre you need something that allows riders to open the throttle with confidence when the bike is leaned over and offers grip to transfer this input into drive.

Tyre timeline: A tyre always offers its best performance at the earliest moment of a race. It’s why riders opt for a fresh tyre in qualifying, but with a full fuel load this can be masked in the early laps. That's why most fastest laps are set after a handful of laps, as riders get more comfortable out there. The tyre will start to drop off during the race, and the best riders are able to delay this for as long as possible. Being able to understand this and not rag a tyre is a key skill for a rider. The goal is to finish a race as fast as possible, and that’s usually achieved by not over-exerting the rubber.


This is part of a series of articles published in partnership with RacingLowdown.com, run by MotoMatters.com contributor Steve English.

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Source: 
year: 
2020

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