Track day tire pressure

tracana

Member
So I've searched the Forum and searched the web and found some realy usefull information on this subject! Supposedly, this is one of the most important and basic "mods" you can do to your car when going to a track day.

For the interested, check out this site: http://www.turnfast.com/tech_handling/handling_pressure

However, since I'm far from being a professional and have little to no resourses, I was wondering if I could benefit from other Z4 owners experience.

I know tire pressure varies with the different set-ups of each car. But I guess any advised tire pressure will be better than the one I use daily :?

My Z4 runs on stock 17'' and (still :cry: ) wears runflats.

If you don't use this wheel size, please let us know the tire pressure you use anyway, it might be helpfull to other people...
 
I don't bother, as there's so much more to it that just the tyres.

If the track temp is a couple of degrees higher or lower then you need to redo your pressures; if you're hard on the car then you may want to increase/decrease the pressure; if it's wet you'll want to decrease the pressures; do you add the extra PSI to a cold tyre, a warm tyre, a hot tyre; etc. etc.

Unless you're racing where seconds count, I wouldn't bother. However, in the first instance you'd get rid of runflats and go for normal tyres, but then if you're worrying about pressures you'll want to go to track tyres.
 
And don't be surprised if the tire pressure light comes on once you've started pushing the car a bit- my car has in the tire TPM and when the weather turned hotter in the spring, it set off the warning light. I've also seen the light come on when pushing M5s and M6s pretty hard (I don't know which form of pressure monitoring device they use)
 
With the ever-worsening British roads and clampdowns on speeding drivers, track days are the only decent opportunity for enthusiasts to give our cars a jolly good shakedown. They are tremendous fun and allow you to explore the limits of your car's handling in relative safety. The key to getting the most out of a track day is preparation and maintenance. Before setting-off you need to ensure that your wheels are balanced, otherwise the vibrations you suffer will numb the feedback through the steering wheel and impair your inch-perfect driving. You do not want to start a track day on brand new tyres, as the large tread depth will cause the tyres to overheat. This in turn will eliminate traction and progressive grip. Conversely you need to ensure that there is enough tread left to get you home after a day of serious abuse.

If you have access to a second set of wheels then use them as you can keep a worn set of tyres on the spares and change the wheels over at the circuit and not have to worry about having bald tyres for the journey home. I know this will not be possible for everyone but if several of you go then you can take a van with the spares in it AND a good way to use those corroded 108s'! Another reason for using spare wheels on a track day is to protect your favourite (and possibly expensive) wheels from damage and corrosion caused by brake dust. The brakes take a hammering and will coat your wheels with extremely hot brake dust, which can eat into alloy wheel lacquer and lead to corrosion. The excessive heat generated by the brakes can also permanently discolour the wheel alloy. Before attending a track day you should carry out a visual inspection of the tyres to ensure they are in good condition. Check for cracking of the tread and tears in the tyre sidewall. The last thing you want is a blow-out at 80mph. If you are feeling really hardcore, you could take a set of slicks with you, but be warned; some track day organisers do not allow them and they will also put some serious stresses on your car. You will also find that the cornering forces you are able to generate with slicks will require you to fit a baffled sump in order to prevent oil surge.

Before going out onto the track ensure that you check the torque of all the wheel bolts and continue to do so throughout the day. When at the track, your main concern is to fine tune the tyre pressures. As you abuse the tyres on the track they will get hot and the pressures will rise so you will want to knock them down a bit to compensate (assuming they were set correctly in the first place). Tyre pressures change by approximately 1 psi per 12 deg F (7 deg C) of air temperature and ambient tyre temperature change - so when air temperature and tyre temperature increases so will your tyre pressures. This means that as pressure increases the tyre profile will alter - you need to achieve a pressure that maintains maximum full tread width from wall to wall on each tyre - not an easy task and yet maintain tyre wall integrity. The best procedure for this is to do one track session and get the tyres nice and warm, then look carefully at the scuffing on the tread of the tyres. If the scuffing does not extend up to the edge of the tread then you need to lower the pressure by a couple of psi and if the scuffing extends onto the sidewalls then the tyres are too soft and require some more air. You need to consider things like the overall weight and weight distribution of the car (the more weight the more air is required) as well as the dynamics of the track.

The outside front wheel of a front drive car will do the most work and so get the hottest. As a result its cold pressure should be slightly lower than the other tyres. The more air you have in the tyre the stiffer you make the sidewall and so the more responsive the car is. This needs to be balanced with maintaining a flat tyre foot print. Low profile tyres have small (and thus stronger) sidewalls and so require less air than higher profile tyres as they will roll off the rim less.

At the end of the day remember to reset the tyre pressures once the tyres have cooled down and carry out a quick check to make sure you have enough tread to get home and that the tyres are not beginning to fall apart. Do not forget to take a tyre pump or compressor with you. It is all very well letting air out of your tyres to account for hot air expansion but you still need some way of being able to replace the air at the end of the day.

I take little credit for this advice as it was given to me and I have merely repeated it for others benefit but after several sessions at the Nurburgring (JUST DO IT....!) I found it to be accurate and ensured and enjoyable experience in safety AND IN ONE PIECE. :driving:
 
jeff spangle said:
Add 2-3 p.s.i. to the normal amount.

:headbang: :thumbsdown:

Your tyres are going to get much hotter than a usual road session, thus will be running under higher pressure. If its also a warm day, you will want to REDUCE them by around 2-3PSI and check the HOT pressure after your first session. If the HOT pressure is around what BMW states, you're onto a winner. Just remember that when pressures are correct, youll need a warmup lap or 2 :)

Make sure, as AlanJ said to take a pump for the end of the day.
 
Good info AlanJ! Although, air is at it's most dense when it is cold, so how come pressure will increase when the tyres get hot? I'm sure it's an obvious answer, and me being thick, but that's just what i'd have thought.

Although, bear in mind when letting pressure out of the tyres, if there is too little pressure in there (or at the beginning of a session, when they are cold) the tyres could get pulled off the rim under heavy cornering. That's what I was told by Andy Walsh on a CarLimits day.
 
dan_i said:
Good info AlanJ! Although, air is at it's most dense when it is cold, so how come pressure will increase when the tyres get hot? I'm sure it's an obvious answer, and me being thick, but that's just what i'd have thought.

Although, bear in mind when letting pressure out of the tyres, if there is too little pressure in there (or at the beginning of a session, when they are cold) the tyres could get pulled off the rim under heavy cornering. That's what I was told by Andy Walsh on a CarLimits day.

The space in the tyre is limited - as the air inside warms up it expands, thus too containt the extra volume of air in the same space means the pressure has to rise to squeeze it in.
 
Thanks for the tips! This has been realy helpful :thumbsup:

I'm not going to race, but if this will keep the car more stable and safe I guess it can't hurt to:
First: check tires' condition;
Second: warm up;
Third: adjust to factory pressure;
Fourth: re-set factory pressure after cooldown (end of trackday);
Fifth: ditch bald runflats ASAP

By the way, a (possibly) stupid question, that factory tire repair kit has some kind of compressor... is that good to re-inflate the tires (for step four)?
 
For Dan:

Charles's law (also known as the law of volumes) is a gas law which describes how gases tend to expand when heated. :thumbsup:
 
And don't forget to reset the pressure monitoring system every time you make a pressure adjustment (or it will drive you nuts)
 
AlanJ said:
For Dan:

Charles's law (also known as the law of volumes) is a gas law which describes how gases tend to expand when heated. :thumbsup:

That's makes sense then. Like I said, just basing my thoughts on the fact that air is dense when cold, I guessed that it would be the other way round. Now I know!
 
AlanJ said:
For Dan:

Charles's law (also known as the law of volumes) is a gas law which describes how gases tend to expand when heated. :thumbsup:
oooh fancy you :D

But I was about to post the same - obviously I've managed to retain some knowledge from uni :)
 
What others have said, AlanJ posted some great info. All I will add, is if it's your first time on the track and your timid it may take more than 2 laps to really warm up your tires. I think it's been said but if it hasn't, check your tire pressure at the end of every session. If you find midway through the session that your car is handling funny (sliding, not stable, etc) pull into the pit and check your tire pressures. Runflats probably will slide/plow even if you have the correct pressure (mine did first event). If your unsure, ask questions at the track, people are super friendly there and will love to give you their tips/advice.
 
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