Will Gray

Tech Talk: The tactics of tyre management

Will Gray

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The Chinese Grand Prix proved again the
importance of managing the new tyres through the course of not only a race but
an entire race weekend - so what are the most important factors the teams have
to consider?

ALLOCATION

First of all, there are four different
types of dry tyre that Pirelli have developed, but they will only bring two of
those types to each race, chosen depending on track-specific criteria such as
surface type, expected temperatures, average speeds, cornering types, etc.

There is no free-for-all on the amount
of tyres teams can use as there are limits to the amount Pirelli can produce
for each weekend, so the teams get 11 sets of dry tyres (down from 14 last
year) per driver to last the four practice sessions, qualifying and the race
itself.

But it's a bit more complicated than
that - and this is what makes tyre management so important, as the degradation
levels of the tyres this year means that the teams must be very careful how
they use their allocation over the course of the weekend.

Three sets (one prime and one option)
can be used on the first day, of which two must be returned. Eight more sets
(four prime, four option) are given out on Saturday but two of these (one of
each specification) must be returned before qualifying. And for the top 10 on
the grid, the tyre they qualify on is the one they must use at the start of the
race.

The usage of tyres is tightly monitored
by the FIA using bar codes on the tyres and, simply put, the more laps a tyre
runs in practice and/or qualifying, the fewer it will last if it is used in the
race.

QUALIFYING STRATEGY

Teams generally keep back six fresh sets
of tyres (three prime and three options) for qualifying and do two runs in each
session (one out lap, one or two timed laps and one in lap).

New tyres produce much more grip than
used tyres, even if those used tyres have done just a couple of laps, so this
is where the balance between qualifying and race performance comes into play.

If a driver can get away with not using
one set during the qualifying session - by being confident enough to do just
one run in either Q1 or Q2 or being fast enough to claim pole without needing a
second run in the final session - they have a fresh set of tyres for use in the
race, which can enable them to do a few crucial extra laps that could make all
the difference as the race strategy plays out.

For example, in Malaysia Lewis Hamilton
had just five sets of tyres he could use for the race because of the choices he
made in qualifying. In China, however, he managed his qualifying with a focus
on optimising his tyre availability for the race itself. He managed to get into
Q3 with two fresh sets of softs left, then decided to do only one run in that
session to save one fresh set for the race.

In doing so, he lost some vital
understanding of how the track feel had developed as qualifying progressed, and
that may have cost him a grid position, but for the sake of one place on the
grid he had secured the advantage of a spare set of tyres for the race.

In the end, the McLaren strategy change
meant he didn't need that extra life in the tyre - but the important thing was
he had it if he'd needed it.

DEGRADATION INFLUENCE

Different cars and different driving
styles affect tyre wear but the added challenge this year is in a lack of
knowledge of how the tyres react to different tracks.

Each circuit has its own level of tyre
wear and it seems the historic data from the Bridgestone tyres does not match
up to the new Pirellis because the constructions and compounds are so
significantly different.

Not only that, but conditions change
throughout the race, with changing track temperatures and tyre pressures
continually altering the balance of the car, and to adapt to this the teams
need to alter front wing settings during pitstops, change brake bias, etc. The
tyres appear to be very sensitive to balance changes, and minor imbalances can
cause major wear so the team that hits the sweet spot at a particular track can
have a major advantage.

The delicate nature of the tyre also
means the ability to react to the unknowns is extremely important, particularly
in this period before greater knowledge is developed.

McLaren admitted after China that they
went into the race not knowing what their plan was. They had a number of
different strategies they could use, and it was left up to the minds on pit
wall to decide which was the best way to go.

Drivers have been speaking about 'the cliff'
in terms of tyre wear this season, and it seems there comes a point where there
is a dramatic drop-off in performance. Get there, and you are in trouble. Pit
just before, and you've made the most of your tyres.

TIMING THE TACTICS

Flexible strategies bring more
complications, however, and one of the most important aspects of making a
strategy work is in the timing of the stops.

Teams have access to a 'car tracker'
system on the array of data channels fed to them by the FIA (fans can also
watch it online), and this is crucial to see the windows where a car could pit,
stop for four seconds, and exit without dropping into traffic. In such tight
competition, there is no room for error - as the windows are not often that
big.

When the performance of the tyres is so
critical, however, and one lap on bad tyres can cost so much, sometimes the
traffic is of less concern than getting new tyres on at exactly the right time.

Take another example from China: Button
stopped one lap later than planned in that race (and did so after accidentally
stopping in the Red Bull pit) and that not only dropped him behind Vettel but
also delayed team-mate Hamilton's pit stop for one more lap, during which the
tyres went over the cliff and he lost a spot to Felipe Massa. In that, McLaren
went from first and second to fifth and seventh - and only recovered by
gambling on a strategy switch from two stops to three.

The difference between a two stopper
versus a three stopper, obviously, is that the three stop will give fresher tyres
throughout the race but, with a stop costing around 25 seconds on average, that
is the amount of advantage that needs to be obtained from that grip.

Any blockage in the track that slows the
pace immediately threatens the success of that strategy - but this year that is
less of a problem because the availability of DRS and KERS. These systems make
it easier for faster cars to get backmarker obstacles out of their way quickly
(particularly when those backmarkers don't have KERS) and it also helps make the
most of the fresh tyre advantage to encourage overtaking right at the front, as
Hamilton displayed in China.

So while F1's new tyre dramas may look
confusing and fast-paced, the strategies don't just play out in the race itself
- they are running right through the weekend.

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