The blueing that occurs on the shoulders is a combination of incomplete oxidation of contaminants. These include oils, mold release agents and silicons from the manufacturing process and contaminants picked up from the track surface including engine oil, hydraulic fluid, brake fluid, ATF, coolant, etc, etc.
IT HAS NOTHING TO DO WITH TIRE TEMPS.
If you look at the surface of a brand new racing slick reflecting the sun at an angle you will see all the contaminats as a rainbow sheen....similar to an oil film on water.
The oils, mold releases and silicons from the manufacturing process are buried deep in the pores of the tire and come "to the surface" as the tire wears and goes through a heat cycle. These are detrimental to traction and counter-productive.
These can and should be removed PRIOR to the tires FIRST heat cycle and during the subsequent next five heat cycles along with acquired track contaminants.
You can use Pro-Blends Race Tire Cleaner, Part # 7050 to remove all the bad stuff.
If you decide to also use a Pro Blend tire treatment, the Race Tire Cleaner is necessary as a prep agent. By itself the Race Tire Cleaner will reduce lap times slightly.
As to leaving the tires in the sun & pre heating:
1. Pre heating a tire may in fact be advantageous, especially on a cool day (ambient Temp v 60*). Some class prohibit active tire pre heaters.
2. Other methods to pre heat tires or keep at optimal temp include:
- removing between heats and placing them in the tow vehicle with the heater turned on full.
- covering with individual passive aluminum "space blanket" type insulation tire "pockets"
- I have even seen the whole bottom half of the car covered with this aluminum sheeting insulation and the engine left running to trap the exhaust heat.
- Left in the sun tires will heat up but unevenly if not rotated. Probably the least effective method.
- Active tire pre heating blankets and pockets are the most effective if allowed.
Conversely on a hot day (ambient Temps ^ 90*, track surface Temps ^ 120*) one may have to cool tires between events.
- keep out of sun
- use a fine mist water spray to cool tires back to optimal operating temps between heats. A small garden fertilizer/insectiside applicator works just fine.
There is no substitute for
A. Knowing your tires correct and optimal operating Temp range.
B. Measuring tire Temps with a probe pyrometer. I recommend Longacre's Digital Memory Probe Pyrometer, Part # 50690
Learn to "read" your tires. Use the pyrometer to tune the starting cold pressure to achieve the optimal hot pressure and optimal Temp. Measure and record inside, mid and outside tire temps and tune accordingly.
For info purposes only, here's a link to Hoosier's racing tire care recommendations:
HOOSIER TIRE TIPS
Hoosier Tire Care Tips
Additionally all racing tires should be stored on their side in a cool, dark place with stable Temp and Humidity. A basement is fine. Be aware that a detatched and unheated/cooled garage can reach cold temperature extremes in winter and be over 120* in the summer and varies widely in humidity...not a good place.
DO NOT transport your car on race tires. The constant flexing while towing in one position can weaken the thin side walls and cause failure and uneven performance at the very least. Change at the track BEFORE and AFTER an event.
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