Tires chunking?

[02#154]

I went to Infineon Raceway for my first track day and had a blast. I have a few questions now about tires:

During one of the driver meetings talk about tire pressures came up. I didn't think I'd be fast enough to worry too much about pressures, but after what ended up being my last session I checked my pressures and noticed that the rubber on the front tires looked "melted". I think it's called chunking? The front pressures hot, just after parking after coming in from lapping were both at 35 PSI. I intended to run one more session so I adjusted the hot pressure down to 32 PSI. I ended up being too beat from the heat and adrenaline to take my last two sessions and left early so I don't know if the change made any difference.

Were my front pressures too high, or too low? Are the tires junk now? If it makes any difference, the tires are S03s. Rear tires were 39 PSI, hot.

J

 

[Hrant]

You are fine :wink:

The heat from your tire and track allowed rubber pieces "chunks" to be picked up that other softer compound tires left on the track. After a few hundred miles, yours will look clean again. But what you experienced is heat cycle of your tires. As you go through a few such sessions, your tires' rubber will harden. Hardened tires will last longer but will grip less and tend to be bouncier and noisier. My last street set had about 50 heat cycles on them with great mileage ......... :tongue:

As for the fronts being 35 psi, that is not much more than the 33 psi. The rears tend to heat up more since that is where the weight is. Tires with higher psi on hot days tend to become slippery. It all depends from where you started to get a picture of how much heat you put in them to get to 35 psi. If you started with 32 psi, then you did not drive hard enough :biggrin:

 

[nsxtasy]

after what ended up being my last session I checked my pressures and noticed that the rubber on the front tires looked "melted". I think it's called chunking?

If they looked "melted", that's not the same thing as "chunking". Chunking means that little chunks of rubber were torn loose from the tread of the tire, typically along the outer edges of the tread.

What were your pressures cold, before you started? Most people find that the best pressures are 32-34 front, 36-40 rear, measured cold. If your rears were 35 hot, it sounds like you started with pressures too low...