Tyre pressures on track?
- Thread starter Easty-5
- Start date
Whilst i did not have an M Z4 i did many track days.
If you leave standard for first run to understand the car, by lap 3-5 you will be experiencing over inflation if you drive it quite quickly.
So, I woud have normally let out up to 5 psi for on track. but be careful on lap one, as the tyre will have to come up to temp.
Its a bit trial and error, but you will need an accurate gauge and an inflator.
Try and do no more than 5-6 laps in each session as this will make it easier on you and the car.
If you leave standard for first run to understand the car, by lap 3-5 you will be experiencing over inflation if you drive it quite quickly.
So, I woud have normally let out up to 5 psi for on track. but be careful on lap one, as the tyre will have to come up to temp.
Its a bit trial and error, but you will need an accurate gauge and an inflator.
Try and do no more than 5-6 laps in each session as this will make it easier on you and the car.
Michelin were at Cadwell Park last Monday at the BMW CC day and I their technicians a few times. We came up with 36 front and 37 rear set about 4-5 minutes after each session. Worked well. You will need a good gauge as most on foot pumps aren't accutate enough.
What are standard recommended pressures? I haven't checked that yet. In my last car I was dropping 5psi at the back and 3psi front once up to temp. I have a half decent Goodyear digital gauge and an electric pump that came with the car. Il have to see if that's any good.
Use a digital thermometer http://www.ebay.co.uk/sch/i.html?_t..._nkw=infra+red+thermometer&_sacat=0&_from=R40 to check your tyre temperatures after you've driven them up to temperature. Hold the thermometer against the tread and take 3 readings on each tyre of inside, middle and outside. You should find that there is a temperature gradient across the width of the tyre where the inside is highest and outside is least with a spread of about 7-10 degrees. You can compare the results from all your wheels, and the rears will be a bit warmer than the fronts, and the tyres which are on the outside turns the most will be warmer than the other wheel on the same axle. The last thing you want is the centre of the tyre being warmer than the inside because this will indicate over-inflation and smallest contact patch. If you then adjust your initial tyre pressures in light of the tyre temperatures after a session, you can then adjust the pressures on individual wheels accordingly. After your next session, check again. You can also use the thermometer to check your brake disc and caliper temperatures too. 
Although the pyrometer approach exdos describes is definitely the best, few people have access to one or the patience to use it properly. Without knowing what tyres you are running and assuming you don't have a temp gauge to hand, then as a rule of thumb I would suggest you aim for *hot* pressures that are the same as your recommended *cold* pressures.
This will mean checking pressures and (usually) letting air out after the first few sessions. Try to leap out of the car and check them as quickly as possible after a session, don't stand around chatting for 5 minutes before you check them, and do the "outside" wheels first. After you have done this three or four times you should find that the pressures stabilise and then you can start playing about and drop or add a few psi here and there.
By "outside" I mean the tyres that are on the outside of the circuit most of the time, i.e. the left wheels on a clockwise circuit, as they tend to work hardest and get hottest fastest. Certainly in the Elise my left front would get hottest quickest (on a clockwise circuit, as they most are).
You will need a consistent/reliables easier gauge and a pump - don't forget to add air back at the end of the day. If you drive home on soft tyres you'll ruin the sidewalls.
This will mean checking pressures and (usually) letting air out after the first few sessions. Try to leap out of the car and check them as quickly as possible after a session, don't stand around chatting for 5 minutes before you check them, and do the "outside" wheels first. After you have done this three or four times you should find that the pressures stabilise and then you can start playing about and drop or add a few psi here and there.
By "outside" I mean the tyres that are on the outside of the circuit most of the time, i.e. the left wheels on a clockwise circuit, as they tend to work hardest and get hottest fastest. Certainly in the Elise my left front would get hottest quickest (on a clockwise circuit, as they most are).
You will need a consistent/reliables easier gauge and a pump - don't forget to add air back at the end of the day. If you drive home on soft tyres you'll ruin the sidewalls.