Sepang - From a tyre point of view


In Malaysia, it is never a question of if it will rain, but instead just a question of when. Today, temperatures in excess of 35 degrees centigrade were followed by torrential rain, which is to set the tone for the rest of the weekend.

For this reason, it is more than likely that Pirelli's intermediate and wet tyres will make their competitive debuts at the Sepang circuit, which was inaugurated in 1999.

For the first time tomorrow, the teams will also try out an experimental compound of hard tyre. Two sets of this new version of the hard tyre will be given to the teams for Friday's two free practice sessions only, in order to evaluate feedback in the demanding conditions of Malaysia. The remaining tyre allocation for the weekend is unaffected.

The hard and the soft tyre will be the prime and option choices for Malaysia, as was the case in Australia, but with rain such a common feature, the intermediate and wet tyres are likely to take centre stage as well.

The intermediate tyre, distinguished by light blue markings, has a tread that is characterised by light grooves across the whole surface of the tyre.

The wet tyre, with orange logos, has an asymmetric tread design. The pattern is denser on the outer edge of the tyre, while a centre channel and two smaller channels of the inside of the tyre help to disperse water more effectively.

The amount of water displaced varies according to the depth of the grooves. The grooves on the intermediate tyre are three millimetres deep, meaning that they can cope with standing water that is around two millimetres deep.

Any more water than that and the wet tyre is required. The moment at which it becomes quicker to switch from the intermediate to the wet tyre and vice versa - the 'crossover point' - is of vital strategic importance, and will hold the key to the teams' tactics in Malaysia.

The wet tyre has a tread depth of five millimetres and is able to cope with a level of standing water of up to five millimetres before aquaplaning sets in. One of Pirelli's wet tyres will clear up to 60 litres of water per second at 300kph, meaning that a Formula One car at full speed will clean up 240 litres of water per second.

The intermediate tyres by contrast clear 20 litres of water per second, as opposed to a road car tyre that can only clear 10 litres per second - but at much slower speeds.

Sepang presents a stark contrast to the first Grand Prix of the year, with hot and humid weather matched to a much more aggressive surface. This should lead to three or four pit stops during the race.

The Sepang circuit is 5.543 kilometres long, with the total of 56 laps that total 310.408 kilometres. The circuit is well known for being tough on tyres, and that is evident from the very first hard braking area into turn one.

The second turn is even tougher: the unevenness of the surface and the stiff suspension means that the inside wheel often lifts, putting all the load on the outer front tyre.

After the opening complex of corners there is a long right-hand bend taken at 250kph, which tends to result in understeer, forcing the driver to make a correction. The front left tyre, which does all the work here, is subjected to a vertical load of 830 kilograms.

As well as the two main straights, unusually separated by a hairpin bend, there is a quick succession of fast corners that impose a lateral acceleration of more than 3G on the car and tyres. The left-rear tyre temperature gradually rises to a peak of 150 degrees on the inner edge while accelerating out of the corner. The famous hairpin bend between the two straights is not only crucial, but a key area of stress for the tyres, combining braking, turning and acceleration at the same time.

Paul Hembery: "Australia went very well for us but this will be another type of race entirely. About the only thing you can rely on here is the fact that it will rain hard in the afternoon and because of this we expect our wet tyres to play a key role here. When it's dry, we expect the hard tyre to be well-suited to the conditions, as ambient temperatures are going to be a lot hotter than they were in Australia. Due to the aggressive surface that we have in Malaysia and the hot weather, we expect to see more pit stops: about three, which could increase to four if the teams have to change between wet tyres, which is more than likely. Before the race, the teams will have a chance to try out a new hard compound tyre during Friday's free practice session. This tyre represents a new philosophy in the compounding and it will be interesting to hear the teams' feedback. Generally speaking it's a more durable tyre but we need to be careful not to be too conservative: the emphasis is still firmly on entertainment and putting on a great show for the crowds."

To experience the Sepang International Circuit in more detail, click here.

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Published: 07/04/2011
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