TrueDrezzer

Hi trackheads,

Got a question on tyre pressures that's causing me headaches in car setup. Here's what normally happens:

I get to the track (Nurburgring Nordschleife) on normally inflated (2.2bar cold==32psi) street tyres. I take a lap or two to warm them up, and they get to about 2.8 bar==40psi. The handling is quite predictable but easy to get them to squeal. So I drop the pressures down slowly, trying 2.7, 2.5, 2.2, 2.0 etc. For some reason, the lower I set the pressure to, the less "predictable" the tyres get, even though I feel more grip. I feel safer in the car with what seems like too-much pressure. An experienced driver took a lap in my car and noted that the front tyres seemed "soft" even with 2.5bar hot pressures.

Anyway, those were with my Dunlop SP9000 tyres, which are now worn out (and had extra wear on the middle from the higher pressures). Now I've got on a set of OEM S-02 Bridgestones, and I'd like not to make the same mistakes again. I started out with 2.2bar cold again and seemed to like how they felt at about 2.5bar hot on the first track day with them. They are far better than the Dunplops in general and far less squeal, too!

Any tips?

///Robin

jguerdat

Given that you're on a track, how about using a pyrometer to determine relative over/underinflation? Feel is part of the equation but a more scientific approach should get you dialed in more quickly. You'll need to read the inner, middle and outer temperatures as soon as possible after a hot lap - don't cool down or wait too long in the pits. Also, don't forget that street tires will tend to overheat in such use - you may have them "go away" if driven too hard for extended periods of time. You might be better off using a second set of wheels with some "R" compound tires (the Toyos may be a good choice between price, grip and longevity).

RedRover

TrueDrezzer, here in Australia we've had quite a bit of track experience with the standard S02s across a variety of drivers.

32 psi is OK for slow street use but quite unsuitable for track work. We recommend you start your S02's at 38 psi COLD and let them build up to about 44psi HOT.

If you find that the tyres are going "off" after a long session then try starting them at 37psi COLD. If it's a slower, tight and twisting track you could even consider starting at 36psi cold.

cdelena

All of the tires I have tried seem to have the best compromise between grip and control if I run them in the high 30's (37-39 psi) when hot. This is not always simple in they will cool on straights and when not pushed and can overheat quickly when loaded very hard. If the tires seem to be getting 'greasy' too often they are too hot and probably need a bit more pressure. The correct starting temperature will vary depending upon the ambient but generally I start about 34 psi cold and adjust during the day as needed. I don't think there is an absolute answer on this as it will vary with car, tires, track, conditions, drivers, etc.

TubeDriver

I gather there is a pressure (hot) on a given day (depending on ambiant temp) and driving condition that provides maximum grip. This may not "feel" the best but will allow maximum g in a turn. I am willing to give up a little grip for better feel but this is not the "Fastest" way to go. For track days try about 36 psi cold, a little less and grip goes up but a squirlly feeling starts in the rear. Adjust as needed. For AutoX, try 34. You have to find a combo that feels good and allows decent grip.

TrueDrezzer

Thanks for the interesting responses. A lot of the track fellows I've asked this question to at the Ring tend to say quite the opposite for some reason. Running about 26-30psi HOT is what they recommend!

Finding a combo between even tyre wear, feel, and ultimate grip isn't as easy as it sounds....

If I recall, 44psi was the MAX pressure for the S-02 as written on the sidewall. Any dangers at running the tyre at 40+psi?

///Robin

TubeDriver

Wow, 26 psi hot I don't know who you have been talking to but thats around 20 psi cold. That is way too low, I have never heard anyone suggest running that low on the track. I get it, your pulling my leg right ?

BTW, the maximum psi on the sidewall is cold psi and there is usually a 10 to 20% fudge factor.


[QUOTE]Originally posted by TrueDrezzer
[B]Thanks for the interesting responses.

TrueDrezzer

Hmm, well the dude was quite experienced, fast, and was running some Yokohama R-compounds, but he was dead serious about the 26psi COLD setting.

Could be a Yokohama thing. Another fellow with a Corvette with Yokohama AVS Sports runs about 33psi HOT on his tyres.

Another thing I've noticed is when my tyres get up there in pressure, say 43psi, part of the sidewall discolours, it seems like the tyre is picking up dust or something and forms a brown ring on them.

Okay, I'll try 36 psi COLD next time and see what happens. The Dunplop tyres felt really good with such settings, but I wore out the insides of them rather quickly.

I tend to drive 1 lap per session (14 miles) and cool off on the main mile-long straight at the end, drive around the town a bit, and park, so I don't really run the car for long sessions.

///Robin

cdelena

Some of this comparison is apples and oranges.. when you have different wheel widths, tire profiles, and tire construction you can run different pressures.

A very low profile racing tire on a wide wheel will respond to much lower pressures than our relatively narrow wheels with tall tires.

The real answer is in your lap times with your gear under certain conditions. Changing the variables changes the answer.

TrueDrezzer

I'm running stock wheels and stock tyres. I was just trying to get some input as to what the effects of various pressure settings feel like, as this is the only car I've driven on a track.

I seem to not notice any significant increase in grip by dropping pressures below 36psi HOT, and the tyres feel predictable at around 42psi or so.

///Robin