Tyre Pressure Rules of Thumb

JoePeps · Mar 16, 2020

I'm still trying to learn but wondering if someone can give me some easy answers to a few questions?

I've got my pressures dialled down pretty well for 23 degrees at Portimao, but how much should I adjust them going to a 12 degree UK day? Should it be more pressure because the track and overall tyre temp won't be as hot in the cooler weather?

If I'm getting cold tear do I need more or less pressure, and vice versa for hot tear?

What would be the lowest ideal temperature for slicks to operate in and probably go to road tyres? Pace wise I'm bottom 25% of the fast group generally.

If it makes any difference I'm using either Supercorsa SP road tyres, or V02 slicks.

bmwbadboy · Mar 16, 2020

34 / 22 on V02s, might start at 24 rear

fast_ryan · Mar 17, 2020

You will find tyre pressure range and compound information here:

Bridgestone
https://s1000rrforum.co.uk/showthread.php?10994-Bridgestone

Pirelli
https://s1000rrforum.co.uk/showthread.php?10842-Pirelli

Follow the advice within the threads above and you can?t go wrong. That said it?s well worth chatting with the track side tyre supplier for any recommendations based on track temperatures and conditions on the day.

fast_ryan · Mar 17, 2020

Cold Tear

A temperature related cold tear generally occurs when the surface of the tyre is much hotter than the core, which is normally just a few mm below the surface. Race tyres are designed to operate at temperature higher that 85 degrees, but if the core is sitting at a lower temperature, it means that the elements that make up the tyre compound won?t work together properly. Pretty quickly you will find yourself with a noticeable tear. The hotter outside compound of the tyre will literally tear itself away from the colder core.

Tyre warmers should be used to help a race tyre get up to operating temperature. Running a race tyre with no tyre warmers, or not long enough on the warmer before use, is a quick way to damage a tyre with cold tear.

Look at what your tyre manufacturer recommends with regards to heat management and stick to it. If they say an hour at 80 degrees, don?t expect them to work properly after 30 minutes at 60 degrees.

Getting the whole tyre, the air in it and the wheel at the same temperature is what you are aiming to achieve. If you can get everything working at a constant temperature, correct compound selection and with correct pressure, you will get the tyre to perform as designed and avoid any tearing.

fast_ryan · Mar 17, 2020

As for using slicks in cold conditions the key is to keep heat in them once out on track after sufficient time on the warmers.

Typically, if track conditions are cold, especially at the start and end of the season, I will normally increase the pressure (but within the recommended ranges). Starting with a higher pressure forces the tyre to reach a higher operating temperature and will help avoid tearing. Be warned that if you are using slicks in cold weather you need to be constantly checking the pressures and temperature before and after every session and making the appropriate changes when needed.

If in doubt you can always switch to a good road orientated sports tyre. They are designed to heat up quickly at colder temperatures and will probably give you the same level of grip in cold conditions if your not pushing.

Monners · Mar 17, 2020

The easiest way to deal with this is to buy a laser surface temp gun. They are only around ?30 and save a lot of hassle if you get you head around the idea of recording track temps.

In the UK, particularly MSV tracks that have slippery surfaces, if surface temp is below 10 degrees then you are playing a lottery on anything that needs temperature to operate such as slicks and cut slick supercorsas,etc. Tyres that are not temp dependent for grip are road tyres and endurance cut slicks such as Metzeler K3 and Supercorsa SP. The difficult thing that makes all the internet and paddock advice near useless is you need to know how the temp changes through the day to be safe which you can use the temp gun for. At the moment it's usually below 10 degrees until around 10-11 o clock so you have to be very careful before that but then can deploy normal slicks after ~11 with relative safety. It usaully stays above 10 degrees until quite late in the afternoon. The outlier is Anglesey which has an excellent grippy surface and remains safer to a few degress lower temperatures.

In places like Spain there's a lot more grip on the tracks so 5 - 10 degrees can be reasonable on slicks.