# First track day complete, I have some concerns though...



## Dirtboy (Apr 19, 2002)

Have you checked the alignment? 

My car had the same feeling when I went from stock 17"s to BBS 19"s. Put the car on the rack and the alignment was off a bit. Put it back to stock alignment and things are fine - rock solid at 140+mph (still just a bit of understeer at the track though  ...)

Check your alignment as well as the other suggestions in this thread.

(BTW- I'm running Bilstein PSS9's and UUC sways- middle setting front and full stiff rear; Michelin PS2's 235/35R19 front 36psi cold, 245/35R12 rear 33psi cold)


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## PunchIt (Dec 24, 2002)

*40 Cold?*

I would disagree, and maybe I'm wrong, but it has been my experience that you want your HOT pressures between 40-42. I think 40 Cold is too high.



Pinecone said:


> WAY low on tire pressures. For all seasons I would be running a minimum of 40 cold. If nothing else, to keep them from rolling off the rim.


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## SergioK (Aug 14, 2002)

I've seen tire pressures go up 10+lbs per tire. Like PunchIt said, starting off at 40 cold is way too high. :nono:


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## Pinecone (Apr 3, 2002)

And in autocross, we sometimes run street tires at 50+ psi.  And bleed down to keep them there.


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## TRWham (Aug 21, 2004)

SergioK said:


> I've seen tire pressures go up 10+lbs per tire. Like PunchIt said, starting off at 40 cold is way too high. :nono:


If you believe that, then you have never run street tires on a race track. But I understand you have, in fact been on the track, so I don't understand why you would say that.


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## SergioK (Aug 14, 2002)

You don't need to take my word for it. Run a cold tire at 40psi yourself, then check your tire pressures after one or two sessions. 

Then again, out here in California, we have a desert climate which means in the mornings it'll be a cool 75f degrees. By midday, the air temps can reach 95f+, with track temps at 135f+. So when I said that I've seen 10+ PSI changes from a cold tire to a hot tire, I am not exaggerating at all.


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## TRWham (Aug 21, 2004)

SergioK said:


> You don't need to take my word for it. Run a cold tire at 40psi yourself, then check your tire pressures after one or two sessions.
> 
> Then again, out here in California, we have a desert climate which means in the mornings it'll be a cool 75f degrees. By midday, the air temps can reach 95f+, with track temps at 135f+. So when I said that I've seen 10+ PSI changes from a cold tire to a hot tire, I am not exaggerating at all.


Check after one or two seesions? Don't you mean check tires before and after EVERY session? And usually with a pyrometer and a pressure gage.

I've seen the same, but lower starting pressures generate even more heat and, therefore, even higher pressure gains. On smaller (205mm or so) and/or taller (>50% aspect ratio) tires, it is not unusual at all to run 40psi cold to keep the tire remotely stiff. I don't have much track experience with street radials wider than 225mm. I do have experience with wider racing slicks, but that is a completely different animal.


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## SergioK (Aug 14, 2002)

Most first time track attendees rarely, if ever, run anything other than normal street tires. Most first time attendees rarely have a tire pressure gauge not to mention a pyrometer. Most first time attendees to track events have a slew of other things on their mind so, as a general rule, when I get in the right seat (and I make sure to ask my students what their pressures are set to), I simply say run at least 32lbs of pressure but no more than 40psi for most street vehicles running normal street tires (these are HOT pressures, not cold). Then again, it all comes down to tire size, type, and track conditions. 

Start off with 40psi (cold-in the morning before driving the car) in a normal tire here in California and you can see increases in tire pressures so high that the tire actually balloons outwards thus reducing the contact patch size and/or exceeds the manufacturer's maximum PSI rating of the tire. :thumbup:


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## Pinecone (Apr 3, 2002)

The manufacturer's maximum PSI rating is for COLD pressures, and take heat induced pressure gains into account. And I have seen 8 - 10 PSI pressure gains on the street.

For a higher profile tire, less than 35 PSI can lead to the bead separating from the rim.

And, we are concerned about the contact patch under load, not under static conditions. That is why the higher pressures.


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## SergioK (Aug 14, 2002)

Pinecone said:


> And, we are concerned about the contact patch under load, not under static conditions. That is why the higher pressures.


If you feel comfortable running 50+ PSI when on track, by all means, go for it. :thumbup:


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## Interlocker (Jun 27, 2003)

TRWham said:


> If you believe that, then you have never run street tires on a race track. But I understand you have, in fact been on the track, so I don't understand why you would say that.


40 cold? Maybe you guys run at 40 degrees ambient temp. too?  I've run my share of all-season tires on street cars and have never set them any higher than 36-37 cold, which would result in about 44 hot.

I could see 40 cold on an all-season street tire for autox, but I'd never suggest that someone run that on track. Again, unless you really are talking about extremely cool ambient temps.


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## Pinecone (Apr 3, 2002)

Why not run the same hot pressures at teh track that you run for autocross. The idea is the same, get the tread and sidewalls doing the right thing UNDER load.


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## Interlocker (Jun 27, 2003)

Pinecone said:


> Why not run the same hot pressures at teh track that you run for autocross. The idea is the same, get the tread and sidewalls doing the right thing UNDER load.


For the same reason that a competitive driver would use different tires for one vs. the other, only on a different level. Most tires would have an optimum operating range in regards to temp and pressure. A 58-second autox run won't generate the same heat, etc. as a 30-minute track session.

I've gone with the more is better approach on these sorts of tires, and have learned that after a certain amount, high pressures start to have the opposite effect you're looking for. A street tire, especially an extremely hard compound such as all-seasons, do require some flex to grip. You don't want much rollover, but you do want the tread to flex to a certain degree. With the pressures too high on track, it becomes similar to driving on solid plastic tires lubed with butter. 

This is all, of course, just my experience and YMMV.


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## The HACK (Dec 19, 2001)

Interlocker said:


> With the pressures too high on track, it becomes similar to driving on solid plastic tires lubed with butter.


 Stuka would love that. SIIIIIIDEWAYZ roolz ju!


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## SergioK (Aug 14, 2002)

Interlocker said:


> lubed with butter.


 :spank:

That's just bad, very very bad.


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## Jim44 (Feb 28, 2004)

SergioK said:


> :spank:
> 
> That's just bad, very very bad.


No kidding.

Olive oil is MUCH better :thumbup: 

Jim


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## Pinecone (Apr 3, 2002)

Interlocker said:


> For the same reason that a competitive driver would use different tires for one vs. the other, only on a different level. Most tires would have an optimum operating range in regards to temp and pressure. A 58-second autox run won't generate the same heat, etc. as a 30-minute track session.
> 
> I've gone with the more is better approach on these sorts of tires, and have learned that after a certain amount, high pressures start to have the opposite effect you're looking for. A street tire, especially an extremely hard compound such as all-seasons, do require some flex to grip. You don't want much rollover, but you do want the tread to flex to a certain degree. With the pressures too high on track, it becomes similar to driving on solid plastic tires lubed with butter.
> 
> This is all, of course, just my experience and YMMV.


Well a wrote a long involved message, with quotes from several top level racing books, but my browser crashed.

Bottom line, too high pressure is much less of a problem than too low of pressure.

Tires get greasy because the tread compound overheats, and tread compounds are more prone to overheating from LOW tire pressure.

As for autoX versus track, the tire temps are similar. After several runs the tire temps get up around 200 degrees, the same as teh track. AutoX has more corniner, the track has striaghts which allow the tread compound to cool (as long as tire pressure is high enough to avoid tread squirm).


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## SergioK (Aug 14, 2002)

Interlocker said:


> lubed with butter.





Jim44 said:


> Olive oil is MUCH better





Pinecone said:


> AutoX has more corniner


My Hai-Ku for the day!  :thumbup:


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## Interlocker (Jun 27, 2003)

SergioK said:


> My Hai-Ku for the day!  :thumbup:


 :rofl:  :lmao: :rofl:  :lmao:


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## Interlocker (Jun 27, 2003)

Pinecone said:


> Well a wrote a long involved message, with quotes from several top level racing books, but my browser crashed.


I hate when that happens!!! 



> Tires get greasy because the tread compound overheats, and tread compounds are more prone to overheating from LOW tire pressure.


I certainly can't argue with that. However, there is a certain "zone" in which the tire works best based on temperature and pressure. One isn't exclusive of the other. When there is too much pressure in a tire, regardless of it's operating temperature, it changes the handling and grip characterstics. Overheating and having too much pressure exhibit similar results, but there is a difference in the feel of those results.



> AutoX has more corniner, the track has striaghts which allow the tread compound to cool (as long as tire pressure is high enough to avoid tread squirm).


While that's very true for brakes, it doesn't quite have the same result with tires in my experience. Rotational friction is still very high when you're driving in a straight line at high speeds, so temperatures wouldn't fall off much. Once a tire is overheated on track, you don't keep at it 100% because you're on a long straight... you'd have to actually notch back speed for a few turns (and straights), if not a full lap or two.

:rofl: :rofl: (sorry... still laughing at SergioK's last comment) haha!


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