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Retired Pipe Polisher C2H6O+
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I'm trying to understand Pirelli's recommended tire pressures for the Supercorsa used on track. As you can see from the chart Pirelli recommends COLD pressures between 29-32 Front and 25-28 Rear. And HOT between 30-35 Front and 26-29 Rear.


At a track day recently I arbitrarily chose 31 Front and 27 Rear COLD to start with. I did not use tire warmers. Seemed to work fine. I was so busy trying to learn the track I had no time to even worry about the tires. They were never a limiting factor. I never checked them HOT after coming off the track for temp or pressure.

Today I decided to see how the tire warmers worked and see where the pressures ended up hot. Mainly because the stated HOT and COLD temps in the Pirelli chart just don't seem to make since to me. There's not enough pressure change to allow for the difference in tire temps.

I've included the data I collected with the bike on stands in my garage. I saw a huge rise in pressure that I would expect going from 65 degrees to 170 degrees.

So how does this correlate to Pirelli's recommendations for Hot vs COLD? If I set my pressures coming off the warmers to what they recommend the pressures would be WAY lower than what they recommend cold after they cooled down.
 

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So how does this correlate to Pirelli's recommendations for Hot vs COLD? If I set my pressures coming off the warmers to what they recommend the pressures would be WAY lower than what they recommend cold after they cooled down.
I have to agree, Pirelli's recommended pressures coming off the tire warmers make no sense to me. Talk to Pirelli.

Your temperature measurements, however, make sense giving the generally accepted target 20% pressure increase (27 to 33 psi) on the rear tire at 170°F. On the track, the parts of the rear tire will heat up to close to the optimum 200°F.

The front shows more (31 to 39 psi) than the target 10% increase but the front won't generally reach 170°F under track conditions. I'd reduce the front cold pressure to 29 psi as a starting point.

I would stay away from the IR type for tire use. They measure the surface temp of the item in the sight, which is great for track or brake or exhaust temps, but not proper for tires, where the temps you are concerned with are below the surface, more in the carcass of the tire.

http://www.longacreracing.com/products.aspx?itemid=1721&prodid=7298&pagetitle=AccuTech™-Economy-Pyrometer
 

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Retired Pipe Polisher C2H6O+
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Discussion Starter #5
I was thinking pretty much the same. Next time at the track I need to take some measurements there to know for sure what’s going on.

I wonder if at my novice pace I actually get the tires that hot?




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I wonder if at my novice pace I actually get the tires that hot?

There's lots of factors you can't control such as track temperature, riding style, tire construction, track design etc. but the laws of physics says you can control tire temperature by controlling tire flex — simply by adjusting pressure. Also, pressurizing tires with nitrogen will eliminate the non-linear effects of air humidity and give measurement repeatability as you test.
 

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Retired Pipe Polisher C2H6O+
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Discussion Starter #7 (Edited)
I hate it when we use the P word. :)

I have observed over time that using normal air (I do use a painters water trap on my compressor since I live on the Gulf Coast) at normal temperatures for Texas that a 1 psi change in pressure correlates to about 8-10 degf in termperature change at the same elevation. And that's pretty much what I saw using the warmers bringing the tires up to temp.


But again, Pirelli's pressure suggestions just don't jive to me. Their cold vs. hot suggested pressures don't follow my observations above.

I need to add that I have complete confidence that Pirelli know what they are talking about. I just can't figure out what I'm missing.
 

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One thing I've learned is that tire pressure that works for others often doesn't work for you. For a multitude of reasons. So, anyone's advice is nothing more than a starting point, and you better be careful at the limits trying those pressures.

When I'm zeroing in on a pressure that works for me, I find a good starting point then after every session I give the tire a visual check for overheating, cold tearing and other pressure related things you can see in a tire. After a while I can get that perfect sandy beach look with little balls off rubber that roll to the edge. Once I have that I note ambient temps, track conditions, and suspension settings in my notebook.

After a few weekends at various tracks I have a full set of data for a range of temps from cool mornings at smooth tracks to mid summer high noon at rough tracks.

I'm a high level intermediate to low level expert who weighs 220 lbs, and I recall first getting supercosa SC's on many years ago. I took pressure advice from a Motoamerica level racer who weighed 140 lbs and was turning near record laps on his perfectly dialed in bike. Hahah, huge mistake.

So my advice is to not take any advice and work it out for yourself.
 

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Retired Pipe Polisher C2H6O+
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Discussion Starter #9
That’s great info from someone with experience. Thank you.


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temp off the warmer really doesnt mean dick.
its all about temp of the tyre immediately after you get off track. ie, how hot is it getting while you are on tracking and smashin' it u. a $30 harbor freight lazer temp sensor light thingie will do the job just great. if temp is too high, raise a couple pounds, if too low, drop a couple.

I tend to run 32psi front when its HOT off the track, and 25psi rear.
some guys like 30psi front, it does give a bit better grip, but i find it really lacks feedback.
the really fast guys run low 20's or even high teens for their rear tyre... but i'm talking like the really really fast guys, not the A group trackday fast guys, not the novice racer fast guys, but the top of the expert club level class guys do such crazy things haha
 
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