At what point do you call a tire no good or unsafe from chunking?

 

IMO what is shown in the picture is very minimal chunking. If that is the worst of it, I would run the tire without concern.

 

It gets worse. There are some spots where a chunk of about .5 inch diameter has let loose.

 

Time to replace. Chunking can go deeper in the tread than what you can see.

 

Regardless of the chunking, the wear bar is virtually at the tread level which means you have 2/32 - 3/32 depth left. Time to replace them based on tread depth alone.

 

Are we looking at the same picture? I don't see wear bars at the tread depth.

 

Outside shoulder seems worse than the other, but still.

 

Ive been looking at the picture you posted again. Chunking means the tire got too hot. Usually the fix is a little more tire pressure. But, sometimes, if the chunking is towards the center it can mean too much pressure and the tire is crowned out. You might want to invest in a bead pyrometer if you do a lot of track time.

 

Barney - You have something stuck in your wheel. I think you hit a snowcone truck...

 

my tires are doing the same thing..