Tyre pressures
Discussion
Maybe a silly question on my part, but I'll ask it anyway.
If you know in general that your tyres pressures are going to rise to roughly xxx temperature on track once you've been out for a session, can you deliberately lower the pressures when going out so that they then rise to the correct amount?
I've a feeling I'm going to be told that no you can't and that the tyres will heat differently when under-inflated on track as opposed to going out on the right pressures, coming in, and dropping back down to the correct pressures again . . ?
If you know in general that your tyres pressures are going to rise to roughly xxx temperature on track once you've been out for a session, can you deliberately lower the pressures when going out so that they then rise to the correct amount?
I've a feeling I'm going to be told that no you can't and that the tyres will heat differently when under-inflated on track as opposed to going out on the right pressures, coming in, and dropping back down to the correct pressures again . . ?
If you are using a car with a comprehensive handbook then it will give both cold, and and an indication of warm pressures, usually a rise of somewhere between 4 and 6 lbf/sq in, but all will give cold pressures.
Nowadays a good digital tyre pressure guage can easily be obtained and they are very accurate.
The cold pressures given in the handbook then need to set before going out, as the tyres will be cold after signing on/noise test/briefing etc and the tyres will then be correct in use.
Low and uneven tyre pressures are dangerous and seriously affect the cars handling.
Also check tyre surfaces both inside and out for blebs or cuts before going out the first time.
Look after them, after all they are your only contact with the road surface! (You hope!)
Nowadays a good digital tyre pressure guage can easily be obtained and they are very accurate.
The cold pressures given in the handbook then need to set before going out, as the tyres will be cold after signing on/noise test/briefing etc and the tyres will then be correct in use.
Low and uneven tyre pressures are dangerous and seriously affect the cars handling.
Also check tyre surfaces both inside and out for blebs or cuts before going out the first time.
Look after them, after all they are your only contact with the road surface! (You hope!)
Not sure if this is perfect, but it works for me using Yoko 032s
I inflate to 22psi the day before the event and check that I have not lost pressure before I go out for about 5 laps. I then deflate the tyres to between 19 & 21 psi depending on how hot the day is and how the car feels in corners. This often means reducing the hot temperature by more than 5psi.
After the next full length run, I generally need to deflate certain corners to get them equal again. I continue to check pressures after each run as they may increase as the day gets hotter.
I leave the tyres at the lower pressure until the next outing
I inflate to 22psi the day before the event and check that I have not lost pressure before I go out for about 5 laps. I then deflate the tyres to between 19 & 21 psi depending on how hot the day is and how the car feels in corners. This often means reducing the hot temperature by more than 5psi.
After the next full length run, I generally need to deflate certain corners to get them equal again. I continue to check pressures after each run as they may increase as the day gets hotter.
I leave the tyres at the lower pressure until the next outing
No offence intended to anyone, but do NOT let down the cold pressures and then rely on working the tyre to build the pressure up to proper operating level. This can damage the carcase.
Start with recommended cold road pressures for journey to circuit. As soon as you arrive at circuit, check pressures, which will probably be 2-3 psi above cold. Leave them there.
When you're ready to commence circuit driving, go out and do maybe two laps at moderate pace. Now check pressures, which will probably have elevated by 4-6 psi. Lower pressures to where they were when you arrived at circuit (that is to say, road warm). Do a few more, harder, laps and bring car back in to check pressures again, and repeat process of lowering to road warm level.
This is what you'd do if you weren't sure what circuit pressures to run. You will arrive yourself at the ideal pressures for a given car, tyre, circuit and conditions, but you want to work down to the right operating pressure. It's a palaver but, as was said, your tyres are the only thing that's connecting you to reality.
(And don't forget to take the pressures back up before you return to the public roads! If it's a two-day track-day, re-inflate the tyres overnight.)
Start with recommended cold road pressures for journey to circuit. As soon as you arrive at circuit, check pressures, which will probably be 2-3 psi above cold. Leave them there.
When you're ready to commence circuit driving, go out and do maybe two laps at moderate pace. Now check pressures, which will probably have elevated by 4-6 psi. Lower pressures to where they were when you arrived at circuit (that is to say, road warm). Do a few more, harder, laps and bring car back in to check pressures again, and repeat process of lowering to road warm level.
This is what you'd do if you weren't sure what circuit pressures to run. You will arrive yourself at the ideal pressures for a given car, tyre, circuit and conditions, but you want to work down to the right operating pressure. It's a palaver but, as was said, your tyres are the only thing that's connecting you to reality.
(And don't forget to take the pressures back up before you return to the public roads! If it's a two-day track-day, re-inflate the tyres overnight.)
Some tyres appear to be very susceptable to failure if run underinflated, where as some competition tyres (tarmac rally tyres for example) have very tough carcases. The Pirelli Corsa and A048, which i have both used have quite tough sidewalls and Pirelli told me they only needed 2 bar to keep them in tact, so that is always my starting cold pressure when i go out,( this is lower than the road pressures i have to use to get to the track to avoid risking a problem over tyre pressures if i was involved in an accident) however i still have to take another 5psi out or so when i get going.
Now then how much are tyre warmers....
Now then how much are tyre warmers....
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