Thursday, May 16, 2013

Dummies guide to the Pirelli compound changes

So Pirelli have finally caved in to the pressure and we are set to have new tyre compounds from the Canadian Grand Prix onwards. We want to take a look at what led to this decision and the significance this decision will have on the 2013 title fight.

Ever since Pirelli have entered Formula 1 in 2011, their brief has been simple - more pit stops and closer racing. The were given the example of Canada in 2010 and told by the powers in Formula 1 that they want more races like that. The dominance of the Red Bull challenger in 2011 was so massive that we couldn't really tell if the tyre met its brief or not. But since they dominated that year, they really had no reason to complain.

In 2012 Pirelli went more aggressive and we had seven winners in the first seven races. The fans loved this while some teams were up in arms saying that nobody understood the tyres and that they were not good for racing. The teams that understood the tyres were happy with it while the teams that did not understand them, were howling, much like this year.



2013 saw Pirelli go even more aggressive and they changed the compounds to make them a step softer than 2012, so that meant 2013 Hard was a similar compound to the 2012 Medium, the 2013 Medium was a similar compound to the 2012 Soft, the 2013 Soft was a similar compound to the 2012 Super Soft and they introduced an all new Super Soft for 2013.

Now if these were the changes we should have seen the same cars that did well last year at Barcelona, do well there again this year because Pirelli brought almost identical tyre compounds - the revised 2013 Hard which was changed to be similar to the 2012 Hard and the 2013 Medium which was the same as the 2012 Soft. The problem is that the difference in the tyres between 2012 and 2013 was more complicated than just the compounds.

The teams faced another issue in 2012 which was that the shoulder of the tyre would wear off and even though the tyre still had more grip to offer it was not available to the driver as it was on a part of the tyre that was not in constant contact with the road. This was due to the side wall of the tyre that was stiffer than it is this year. Due to the stiffer side wall and the inconsistent contact patch the drivers also experienced issues where they could not get the tyres upto temperature.

This year the construction of the side wall has been altered to allow the entire platform of the tyre to stay in contact with the asphalt, giving it a larger contact patch and allowing the driver to have access to all the grip available on the tyre. This required the tread platform of the tyre to also be changed as otherwise it would wrinkle under the forces of acceleration, braking and cornering.

Another change from 2012 to 2013 in terms of construction of the tyre was that a steel belt was used for 2013 up until now whereas the 2012 tyres had a Kevlar belt. This also could have had some influence on building temperature in the tyres and being able to manage that temperature. Some experts expect Pirelli to shift back to using Kevlar as it's use has been proven in 2012, without the delaminations that some drivers have experienced this year.

Exhaust blown diffusers (ebd) were banned in 2012 and the teams have developed the coanda exhaust to counter the effect of the ban, atleast to a certain extent. The ebd and the coanda exhaust help the aerodynamics of the car in a similar fashion, though not as efficiently with the Coanda. As seen in the image below, the tyre squirt (air dispersed by the tyres of a car while rotating) can come in the way of and disturb the efficiency of the rear end of the car thereby losing the downforce it is designed to generate.

Image courtesy somersf1.blogspot.in 

The softer sidewalls of 2013 affected the grip levels around the exhaust area because of two reasons. One is, due to how much the sidewalls move the levels of tyre squirt and aero interference in the diffuser are increased while cornering, braking, accelerating and going over bumps. The second is that it affects the downforce or grip levels due to the reduced ride height upon compression of the sidewall of the tyre. A Formula 1 car is a highly tuned machine and every measurement is calculated to a millimeter and the effect of which is magnified as you go faster and faster. The ride height of the cars are used in increasing downforce and managing the balance of the car.

Now after all teams have worked on their cars through pre-season testing and five grands prix, Pirelli have decided to change the compounds apparently only due to the number of pit stops in Barcelona. We are pretty certain that these changes could affect the pecking order and most certainly will.

The team to most benefit from these changes will most probably be Red Bull. Once the teams were given a brief on the 2013 tyres in 2012, teams like Force India, Lotus and Ferrari focused the design and development of their cars on managing the temperature of the tyres (by keeping them in the ideal temperature range) and ensuring they were not too hard on them. Lotus and Force India have done the best job in terms of that, with Ferrari not far behind. Ferrari seem to have found a sweet spot with their aero balance and tyre wear, as emphasised by their four stop win in Barcelona over Lotus's three stops.

Red Bull on the other hand have a very efficient aero package, but an inferior mechanical package which doesn't allow them to manage their tyre temperatures very well. This was not a problem last year as the tyres had a much wider operating window, ie once the tyres came on and were upto speed, their optimum temperature range was much wider than the tyres that were used this year. This year the tyres get upto temperature easily, but their optimum operating range is much smaller than last year. So once we go back to those compounds and change the construction of the tyre to 2012 spec, we can expect tyre management to have a lesser role to play in the race results.

By effect, all the work done by Ferrari, Lotus and Force India could be negated by this move to change the tyre compounds while making Red Bull stronger. But another way of looking at it, is that if some of these cars are kind to the 2013 tyres they should also be kind to the 2012 tyres and maybe still make a pit stop lesser than Red Bull. Interestingly enough, it could also bring back the likes of McLaren, Williams and Sauber into the fray who have sort of lost their way between 2012 and 2013. Mercedes could lose out on some qualifying pace but they could gain quite some in the final race results due to the wider operating range of the tyres.

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