Tech Talk -
Dec 12, 2012
Getting the best from your tyres
Getting the best out of your
tyres is a vital element in racing and often one
that drivers fail to fully comprehend leading to
a variety of inaccurate conclusions.
Interestingly if you watched that last action
packed grand prix from Brazil you’ll have seen
just about every possible complication to tyre
performance, from overheating with a track
temperature of 50 degrees to struggling for grip
in low temperature damp conditions.
There are a few golden rules but aside from that
then it very much comes down to you the driver
(or Dad sorting son) to make the best of the
So the golden rules are:
- Pressure makes a huge difference to tyre
temperature. So if you have 10psi in your
tyres they will heat up far less and more
slowly than say 30psi. As a tyre gets warmer
the pressure will also increase by a few
- Softer rubber gives more grip but wears
quicker. But there’s not much you can do
- The wider/larger/flatter the tyre the
longer it takes to warm up.
- Many tyres – especially wets – are
directional and it is vital they are fitted
the right way round. Check and double check
because mistakes can happen even at the
- Our tyres (unlike F1) do not give their
best performance straight out of the box.
They can need some use to be at their best.
- Rubber doesn’t like to be too hot or too
cold to give its best performance.
- Track surface can make a big difference
to grip levels and also to how much the
tyres heat up.
- When switching tyres you must take into
account gearing which will need significant
change to get the best performance.
Of all those points there are
really three areas that stick out as being of
prime significance and in our control as
drivers. That’s the pressure/temperature
element, the wheel rim width size which affects
tyre shape, and the gearing required.
For most of the year the temperature in this
country falls into a mid range of around say 10
– 17 degrees C. And broadly within that tyres
will work fine. So with the Maxxis tyres we use
generally the slicks should be pressured at
around the 12 – 15 psi area and they will work
fine. And similar for the new wets.
However at extremes of temperature you need to
be much more thoughtful in your settings. So if
it is a red hot day at say 25 – 30 degrees C
ambient and a lot more on track, then you will
need to lower the pressures or else you will
cook the rubber which will give less grip and
maybe even damage the tyre for further use. So
as low as 8psi might be needed for slicks.
And at the other end of the scale with low
temperatures you’ll find the grip suddenly drops
away like falling off a cliff. And tyre
temperature is more important than whether the
track is wet or dry. A hot tyre will work on a
wet track, but a cold tyre will not.
Maxxis themselves do a great deal of research to
develop tyres and their insight tells us that
for the slicks somewhere between 70-80C is an
optimum temperature to work in. Above 90C they
lose grip. For the wets you need to be somewhere
around 40 – 50C for best results. Much above
that and again you lose grip.
It is also
interesting to note that road tyre manufacturers
and car makers suggest 7degrees C as the point
at which you should change to winter tyres
because the grip will have fallen off so much.
Winter road tyres are designed to work at lower
temperatures in terms of compound and tread. We
don’t have different tyres for the cold but we
can do things very differently to make our race
So for both wet and dry
tyres you need to use a lot more pressure. It is
impossible to be exact because there are so many
parameters such as the weight of the kart
(Junior or Senior), the nature of the track
(some have grippier surfaces then others) and
nature of the kart.
But the simple rule
is that you need more air in the tyres to make
them work. How much is the bit you need to
experiment on. With wets on a cold wet horrible
day you may well need 40psi to get them turned
on and working effectively. And with slicks
maybe as much as 30psi.
Especially with wets the wheel rim width can
make a big difference too. The new wets have a
flat profile and need probably a 130mm front rim
and a 180mm rear rim for best performance in
normal conditions. But when it is very cold
maybe a narrower 120mm front rim with a 140 or
160 mm rear rim will help them work harder so
they get some heat build up.
the wet is complex because on the one hand you
are going slower round the bends and the
straights are shorter because you have to brake
earlier, but on the other hand sometimes
slightly lower gearing can help give you more
traction instead of wheelspin.
vitally important to note that whereas the old
Maxxis wets were smaller diameter than the
slicks, the new ones are a larger diameter. That
means you have got to put a lot of extra teeth
on the axle sprocket to get the same gearing
increase over the dry tyres.
on the old wets drivers were putting on say 3 or
4 extra teeth. With the new tyres maybe 8 will
be needed on the axle sprocket. Or of course you
can switch from the standard 10 tooth to a 9
tooth engine sprocket to get roughly the same
That’s going to be an area
where testing and experience are required to
fully understand the maximum that can be
achieved with the tyres.
To get the
maximum from your tyres and kart at all times
I’d suggest keeping a very careful log of track
temperature, gearing, tyre pressure, and the
tyre temperature when you come off track. Actual
track temperature is more important than ambient
temperature so bear that in mind.
the job properly you need a heat measuring gun
which gives an instant read out of temperature
on anything you point it at. It is not as
accurate as a proper tyre temp gauge which
measures inside the rubber but it does give you
a very clear picture of what is happening.
Use the heat measuring gun to check the track
temp. So if you see that with a track temp of 10
degrees you got good grip on 17psi then you know
where to start from.
Remember match your
tyre pressure to the track/ambient temperature.
Don’t expect tyres to work instantly at their
best whether new or old. And make notes on what
you do to achieve best results.
do remember that new tyres will always have a
certain amount of releasing agent on them which
gives zero grip. It is so embarrassing to spin
coming out of parc ferme onto the track so get
them warmed up and bedded in before you start
Formula TKM Co-ordinator