tyre pressure for track day?

[89lude]

Hey guys, i'm going to the track this weekend and i've got a new set of wheels which are 16 inch rims. I've always had 15" so i'm unsure what tyre pressure i should run for optimum grip as the max psi on the 16's is 51psi.

I have some wedsport tco5's in 16" with falken rt615 tyres 215/45/16.

Any suggestions on tyre pressures would be of great help.

[munkaii]

With good street tyres like those I think you should be looking at around 40psi HOT. Around 34psi cold and give it some hot laps and then check the pressures straight after the first session.

[89lude]

any suggestions for the specific front and rear pressures?

extra info: i drive a dc2r with stock sway bars, cusco zero 2's. the car is fully stripped out other than door cards and dash. front and rear strut braces. dont know if the change in weight distribution will matter.

obviously i'll tweak on track but just wanting a starting point for my first session.

thanks

[SpoonS]

generally for ff cars you run the back higher then the fronts cold, coz the fronts do more work. For street tyres i ran it hot at 45psi, so i started the rears at 40 and the fronts at 38, and adjusted accordingly.

[munkaii]

Would 45 psi hot be too high for not enough of the tyre to be in contact with the ground? I thought 40 was around the limit but correct me if I'm wrong. Happy to learn.

[SpoonS]

Would 45 psi hot be too high for not enough of the tyre to be in contact with the ground? I thought 40 was around the limit but correct me if I'm wrong. Happy to learn.

With street tyres, you want to keep the pressure high like that because the sidewalls aren't as strong as say a semi slick. Ive seen people run with 40, and have shredded their tyres. I guess it all comes down to what brand/model tyres you use. Also, that american pro driver guy that goes to the circuit club track days told me to run it at 45, so i did :)

[89lude]

anyone else have any input? more specific to my setup. thanks

[EG9]

I run the same pressure in my 15s as I do my 16s. Front around 33-34psi, rear 36psi cold, when hot works out to 40psi front 40psi rear.

[RandyRhydah]

Yeah at my first drivers briefing they said run 40 psi on the street tyres,

What do people recommend for federal RSRs? They aren't quite a semi slick but they are superior to a street tyre.

[DLO01]

Cause they are cheap for people on a budget. But with everything, its pros and cons.

[89lude]

when you guys say 'hot', after driving around for a long time 'normally' is that considered hot? or is that considered cold and when i get on the track its going to be hotter?

[EG9]

Hot is after a track session, trust me they're going to get much hotter than any road driving you can do.

[1590cc]

I've been running 24-25psi... gets to around 30psi when hot on R888 and V70A

[89lude]

that would be because you have a semi slick with a stiffer side wall? is that on a 16 inch rim/tyre just for future reference as i would like to upgrade to some r888 in future

[AE092]

I just did a track day with a few guys (novice/new to it all) and I recommended 32psi front and 34psi rears - cold. Friend was on Toyo Proxes T1R so not too far off your Falken RT615's (more comparable with R1R's) but regardless, once he lowered it down to them and got used to it, he managed to go 3 seconds quicker (after I showed him the lines he could work with). Here's a tip, don't go lowering your tyre pressure all the way down at the beginning of the day, start of gradually until you find the psi that suits your driving style. Some guys like it higher/lower than others. If you lower it too much on the day and do not have the opportunity to reinflate at the track then you'll have to make do.

I was on semi 15' RE55S semi slicks: 26.5psi all 'round, after having 28psi caused my rear end to be too tail happy and lose it into the gravel.

[integragsi96]

what would someone suggest i run on kumho ku36's 225/50/16?

[AE092]

When I had KU36's, I kept it at 29/30psi cold. They are dependent on the temperature of the day, the hotter the day the faster/more they'll heat up. I had the 205/50/R15 size, tire pressure recommended is for track. For street, they stayed at 33/34 psi all 'round.

[rpm boy]

what are the rim to tire width percantages you guys are using also? there isnt alot of information out there in relation to corner weighting, tyre footprint ans rim/tyre width percentage. would be good to get some decent info and also setups with track times

[gbpracing]

With street tyres, you want to keep the pressure high like that because the sidewalls aren't as strong as say a semi slick. Ive seen people run with 40, and have shredded their tyres. I guess it all comes down to what brand/model tyres you use. Also, that american pro driver guy that goes to the circuit club track days told me to run it at 45, so i did :)

SpoonS has it right, street tires are needed to be higher pressure for the track due to the weaker flexable sidewalls. The tires can get chopped out due to tread blocks moving around under load. Eventually tearing away.
If your going to do track days get a spare set of wheels and semi slicks and enjoy the lap times tumble. Save your good street tires for the street.

[Stevil]

89lude I run Fed RSR 205/50/16 at the track (Done probably close to 500 laps at 7 track days) and they are a simlar tread wear to your RT615. Now I've played with everything from as high as 45 down 32 and I've come up with 38psi for the front 36psi for the rear. The RSR do have a stiff side wall but seeing as your 45 profile is a little less I'd expect you best pressure wont be far off this.

Randy 40psi is gunna be too high for the RSR I reckon, I set my best times when track temp got to 29C back in Feb, was running 38F/36R. keep in mind my FD1 is fairly front heavy with 60/40 weight bias.

[munkaii]

There's a few factors that need to be considered when deciding on tyre sizing and tyre pressures.

As some people have mentioned, street tyres have less stiffer sidewalls than semi-slick tyres and hence you NEED to run them at a higher pressure. There are two main effects associated with this:

1. Higher tyre pressure --> higher sidewall stiffness --> the tyre is able to retain shape as opposed to rolling over excessively and potentially separating from the rim.

2. Higher tyre pressure --> smaller contact patch area --> less grip but better TYRE WEAR. A lot of people still run low tyre pressures because they want to gain that additional grip, however you run a much higher risk of the tyre falling off the rim and you will shred tyres significantly quicker.

If you wanted to think into it further, lower tyre pressures would mean better lateral corner grip in the sense that the contact patch is greater at a sacrifice to the rolling behaviour of the car. A car with lower tyre pressures will roll more, which actually reduces cornering grip. So it's a compromise between the two. Higher tyre pressure is always safer for a street tyre.

[89lude]

Thanks for info guys but this thread was bumped by a question above which should be answered instead of mine. This thread was from almost a 18months ago :)

[r3ckless]

Point beiing? Its always good to have these informative threads for new pnes comming in and wanting to know about tyre pressures.

[rpm boy]

How is everyone actually testing there tyre pressure and contact patches for best grip? is everyone just dong trial and error and associating there pressures with lap times or are you setting the pressures, checking the contact patch and then trialing it on the track?
i think everyone on here has the right idea but does anyone have an example of how they actually check there contact patch/ tread pressure contact on the road....

[Stevil]

rpm boy I check tyre temps with a pyrometer as soon as I pull up along with tyre pressure. This gives a good idea as to what part of the tyre is working hardest. Overinflation of a tyre will show the centre of the tyre hotter than the outside. Too big a difference beteen the outside and inside tyre temps is a good indicator that you could run more camber.

As long as traffics not too heavy Racechrono on ya mobile gives good feed back to whats working and whats not.

[rpm boy]

yeah i usually just check the tyre with a infrared temp meter (pyrometer) but was wondering of there was a "scale" type device that you could roll onto after a race and measure load/heat pattern of the tyre to determine the tyre contact.......its way overboard of what i really need but just a curiosity thing really

[munkaii]

I think some racing teams, rather than using a scale will use infrared heat sensors mounted near the wheel well to observe temperature changes on the go. I'm not sure about temperature loss on cooldown, but a tyre generally loses about 1 psi on the cool down lap.

The tyre temperature at the surface is also used to estimate the approximate internal tyre temperature and with a bit of applied mathematics is not a bad approximation for tyre pressure.

[rpm boy]

might be looking into a kit that determines tyre pressure whilst driving, i assume it would work like the new cars use run flat tyre indicators and determining rotational speed depending of circumference of the wheel, not sure how accurate this will be but always good guestimation as you loose a couple degrees when comming back to pit so would give you a little extra info if correct.still would be awesome to have a machine like footlocker to show pressure and heat zones :p

[lil_foy]

Just adding my 2c from experience, I ran 30F 32R cold on my 205 50 15 rsr and they usually got to around 36~38 hot. I found this to be a good pressure for them, wear was nice and even.

[gbpracing]

yeah i usually just check the tyre with a infrared temp meter (pyrometer) but was wondering of there was a "scale" type device that you could roll onto after a race and measure load/heat pattern of the tire to determine the tire contact.......its way overboard of what i really need but just a curiosity thing really

One thing I look at and its quite valid is how the tire is wearing across the contact patch, this info can tell you if you have poor geometry settings which can cause over heating and wear on the inside or outside edge of the tire. Over inflation will be felt rather quickly on the race track, as the feeling will be like your on ice. I once had my tires filled with nitrogen thinking I could then inflate to the optimum pressure of 38 psi and thinking it wont increase but big mistake, their was still enough moisture in the tire to cause a positive pressure increase. After 2 laps my car started to slide all over the place, I though I had a flat at first so I came in and found my pressure went from 38 to 45psi. (Bridgestone Potenza RE55)