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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. 

And whether you are racing in karts, touring cars or Formula 1, the same challenges apply as far as obtaining the best results across different temperatures and conditions. Let’s give you some help. 

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 conditions.
 
So the general 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 20psi. As a tyre gets warmer the pressure will also increase by a few psi. With the wet tyres the simple guide is that the wetter it is the higher the tyre pressures and the dryer it gets the lower the pressures.
     
  • The wider/larger/flatter the tyre the longer it takes to warm up.
     
  • Tyres are directional and it is vital they are fitted the right way round. Check and double check because mistakes can happen even at the highest levels. 
  • 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. It is always best to bed in the tyres for a few laps before you push hard as this will prolong the consistent life of the tyres.
     
  • 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 with different circumferences then 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 C. And broadly within that the tyres will work fine. So with the Maxxis tyres we use for TKM generally the slicks should be pressured at around the 10 – 12 psi area and they will work fine. 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 C ambient and an even higher track temp, then you will need to lower the pressures or else you will overheat 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, but if setting this low we advise the use of bead retainers on the wheels.

And at the other end of the scale with very 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, so as high as 16 psi might be required.

Maxxis themselves do a great deal of research to develop tyres and their insight tells us that for the slicks somewhere between 70-80C tyre temp is an optimum range 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 suggest 7 C ambient 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 tyres work.

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 track surfaces have more grip than others) and handling traits 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 20psi. 

One indicator on whether your pressure is about right will come from pressures. If the pressure increases by about 1-2 psi when on track then it is about right. Much more than that and you know you have tyre pressure too high.

Especially with wets the wheel rim width can make a big difference too. The 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.

Gearing for 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 wheel spin.

It is very important to note that the latest Maxxis wets are a larger diameter than the slicks.. 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. But because they are bigger it does automatically raise the ride height which is a definite bonus.

Typically you might add on 8 teeth on the axle sprocket in very wet conditions. Or of course you can switch from the standard 10 tooth to a 9 tooth engine sprocket (direct drive engines only) to get roughly the same increase without changing the rear axle sprocket. That’s an area where testing and experience are required to fully understand what can be achieved with the tyres.
 
To get the maximum from your tyres and kart at all times keep 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.

To do 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 15 degrees you got good grip on 12psi 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.

Finally 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 really motoring!