Tyre Pressures On Track Days?

[TerryF]

Hi there,

I'm new here so please excuse if I mess up? I have done 3 track days at QLD Raceway on street tyres so far. What pressures do you guys run on track days? I ran 34 cold and they seemed not too bad for cheap road tyres.

I have scored a set of used slicks and another set of semi slicks. What starting pressures would anyone reccommend??

Terry

[benjam]

Yeah I think last time I ran 34 cold as well. I was aiming for 40 hot, so the easiest way is by tiral and error, so measure what you want hot (maybe max pressure rating for that tyre written on the sidewall), then go for a run, measure, top up or down and before the next run measure cold.

But the best way is to not even worry to much about pressure. Some guys use a pyrometer basically measuring the inside. centre and outside tyre temps. If all 3 are equal after a run, then you have perfect pressure. Colder in the centre, means needs more pressure, colder on inside and outside means less pressure needed. Also useful to test how successful suspension setups are, ie camber/caster/tow out.

Edit: For road tyres, the sidewalls are designed for comfortable road use, so the sidewall is not as strong as a tyre designed for racing. That's why higher pressures are usually needed. For slicks or semi racing tyres, best to find out what their ideal operating pressure is. Most manufactures have this info on their website about their motorsport tyres. Or search google. :-)

Ben

Edited 05/10/08 02:48 AM by benjam

[R-SPEC]

I was going to ask this question as I start my first of many track days on friday. Thanks Ben

[EZ2CME]

I thought that when you take it to the track you should be running closer to 45-50psi in the tyres. Isn't that what they tell the FPV guys when they do there track day?

[R-SPEC]

Probably coz they're all still running the disgustingly awful Dunlops

[benjam]

Yeah I did a driver training course which was mostly a series of stop/start manuvours and we setup tyres at 40 cold. Considering we weren't doing laps this is fine. But my first ever track day in my old Alfa, I did the same, 40 cold and by the end of about 10 laps they were 52 hot, which was way more than recommended max for that tyre. Depends on the tyre, a 65/70 series profile tyre on my Mum's old Nissan is rated at 35 max.

If I put 40 cold in my 30/35 series 19" tyres I really feel uncomfortable on the normal road. 35 is much better, though I have bigger sway bars, stiffer springs and nolathene bushes too. :-)

Ben

[Erko]

I use 40psi front and 38psi rear cold as a starting point.

the falcons carry a stack of weight in the nose and tend to try to fold over the front sidewalls at lower pressures...the higher pressures dont solve the problem but it helps.

[FastR1Red]

As you know every tyre is different, every track is different. So what pressure you run on 1 track doesn't mean it'll be food for the next track either.

It's a pretty complex art but some good starting points:

Start with 38 front and 36 rear and do 1 full session.

As soon as you return take the pressure readings from all 4 tyres. Wherever you get more than a 10% increase in pressure go down 1-2psi, wherever you get below a 10% increase increase by 1 psi. Do another session and check. By the 3rd session you'll be pretty much spot on but remember as the day progresses and the track temps warm up, you'll have to drop pressures a little.

So if you're on a pretty tight track you may find the rears have spun up a bit and gotten a little hot say to 42. That's a 14% increase. Drop them by 2psi to 40 hot and go for your next session.

Really that's very basic, cos what will happen is the car will probably start squirming a bit when the tyres get hot, could it be your pressures, your tread, the suspension or the tyres going off? Pretty difficult to tell unless you have a look at the tyres. More than likely if you're running the standard Dunlops they'll be pretty feathered and you know that's the problem, raise the pressure a little to compensate for cr@ppy tyres and soft sidewalls.

Lots of things you can do, just experiment to what feels best for you on that track. Make sure you have a VERY accurate pressure guage with you.

TRue what EZ2CME says with running high pressures, a lot of guys just don't drive hard enough to build up enough heat to start with, so starting with high pressures, albeit a little slippery, may be a good starting point. You'd want to have your springs in pretty good condition though.

[benjam]

I did my track day today at Wakefield Park which is pretty tight and twisty. I started with 34 cold, and all 4 ended at 38 hot. So I after they cooled down, I put them up to 36 cold. After the next session they ended up 40 hot. Interestingly I just found my max pressure rating for my tyres is 50psi (Yokohama Advan Sport V103), so I could have tried a little more, maybe next time.

Ben

[TerryF]

Ok thanks for that guys.

Regarding the Slicks and semi slicks. What pressures in them please as a starting point? I heard slicks start at VERY low pressures.

Any idea's please. I have a second hand set of both and was going to test the Full Slicks first.

Regards

Terry