I just swapped my track wheels off the car and put the street wheels back on, having just done a day at the track. Well, looky what we have here:

(good and bad tires)

I guess that would explain some of why I wasn't getting near my best lap times!

The rear tires as shown have 2 days of wear. The fronts, which are beyond shot at this point, have been used for 6 or 7 days. Before this event, they looked like they were on their last day, but no where near cording. The tell-tale sign that the cords are going to show up during the day, is the circumferential cord ridges in the remaining rubber surface, which you can see in the rest of the tire in the picture below, where the cord is not yet exposed.

(close-up)

What's a little odd is that where the tire finally wore down to the cords was on the inside edge of the mainly unweighted tire. (Thunderhill runs counter-clockwise, and this was the front left tire.) On the only right turns (T3, T6, T14/15), this tire gets hard wear on the outside (the relatively unworn side) because of the lack of sufficient negative camber. On the rest of the track (left turns), the front left tire would seem to not be doing very much. But I guess when the car is in a fairly hard left hander like T1, T2, T9, T10, T11, even though the left front tire is not bearing the brunt of the cornering weight, it is sort of getting dragged across the pavement with extra negative camber; maybe that explains why the inside of the unweighted tire could get this kind of wear.

So...

Note to self: Next time, get on the ground and check the inside tire edge between sessions ya idiot! Don't assume the outside will wear faster!