How quickly do tires cool down?

Alright so I want to know, from your experience, how long does it take for your tires to cool off after say, a 30 minute session on track?

I ask because tomorrow night my local track is having a 3 hour open session track night.  I have done 8 track days now but never an open session. Usually I have 40-60 minutes to sit around after each 20-30 minutes while my car cools off.  Tomorrow I won't have that. 

I run 340 TW Michelin PSS *BMW (the ones off an M3) on my 07 350Z (3200 lbs.).  I like these because I can push the car right to the limit and it's fun because they let go really easy and I can just play around with the chassis.  I know they are not a track tire.  This is why I worry about them overheating and delaminating (I did this with some other tires).  At $1370 a set.... Not what I want to do. 

How long should I give the tires between each session to cool down in the three hours?

I spray the edges with water after each session.  This lowers the temperature much faster some old guy told me one day. 

Tires cool pretty quickly, enough so that if you want accurate tire pressures you check them in the pit lane after a hot lap.  Doing a cool down lap and checking them in the paddock after you get out yields numbers that can be 1-2 psi lower.  You can probably keep the tires OK without even coming in by just doing a slower cooldown lap every N hot laps.

One of the other things to be concerned about when doing extended sessions like this is transmission and differential temperatures.  I dunno if that's specifically a concern with the Z, but in general endurance race cars often have coolers installed on them to avoid destroying bearings with heat.

In reply to codrus (Forum Supporter) :

Awesome info, that's what I was looking for.

So I asked my other buddy about the diff and trans.  He says the trans are solid as guys Enduro race these things on the stock trans with no coolers.  The diff I have extra capacity cover with a boat load of fins build in.  Got an OS Giken unit back there so I really wanted to protect my investment.

Re-reading your original post, I should note that I've never tried extended sessions like this on a genuine street tire like a Michelin PSS.  Semi-race tires (NT01s, RS4s, etc) do fine with extended running with just occasional cooldown laps.  Full depth street tires might be different -- I'm kinda waffling on this. :)

In reply to codrus (Forum Supporter) :

Yeeaahhhh I still don't know... I packed the car up with the track box.  I'll drive it to work. I have until noon tomorrow to sign up.  In hindsight I should have just gotten the Goodyear SC3 tires. Problem is it's usually cold here so the PSS let me drive it a few more months a year.   One day I'll get another set of wheels for track tires

Take a sprayer 

 I once did an event with a 6 hour window; I pretty much did 30 minutes on and 20 minutes off.

In reply to Tom1200 :

What tires were you running? 

Bmsluite said:

Yeeaahhhh I still don't know... I packed the car up with the track box.  I'll drive it to work. I have until noon tomorrow to sign up.  In hindsight I should have just gotten the Goodyear SC3 tires. Problem is it's usually cold here so the PSS let me drive it a few more months a year.   One day I'll get another set of wheels for track tires

If it were me I'd go do the event, run about a 50% duty cycle (20 on, 20 off, say) and keep an eye on the tires.  If they start getting greasy then don't continue to abuse them, do a cooldown lap and come in to inspect.

In reply to codrus (Forum Supporter) :

I opted to not go.  Next track day I will check temps in 5 minute increments after a run to see how fast they cool down.  Running around trying to time sessions out for 3 hours so my stuff doesn't get destroyed didn't sound like a ton of fun.  I am just going to go fishing tonight instead lol.

You'll be fine with the tires.  They won't give you trouble.  Other things might need more time to cool off but not your tires

I don't think those tires will be much of a problem.  I've abused some (presumably similar?) PSS pretty badly on my Focus RS, but sadly only for about 25 minutes at a time because at that point the oil temp is 290F and the AWD system has disconnected.  They got a bit melty, but no problems with another couple years of street use.

And tires cool off really fast.  A single cool down lap dramatically changes race tires, and after about 10 minutes they go from being goo that'll pick up huge rocks to pretty solid again.

I once did 2 tanks of gas in a Miata on Toyo street tires, only really stopping to fill up the tank.  They were used up, but fine.