What is

"Chunking" is when the bond between the tire tread and the main body (carcass) fails, and large pieces of the tread fall off of the tire. Most motorists will remember seeing large pieces of tire tread left on the side of the road by passing 18-wheeler trucks. This is a similar problem aggrevated by the routine use of retreaded tires in the trucking industry.

Most enthusiasts who experience chunking are road racers of some type. This is because the tire heats up much more during racing. A race tire also experiences much larger forces due to cornering and its own rotational speed.

From Keith Sontheimer in the May 19, 2002 Digest:

"I've been told by several tire experts, chunking happens when a tire's tread heats up unevenly (top to bottom). If the outside of the tread block closest to the road heats up substantially quicker before the rest of the block closer to the carcass does, then chunking can occur.

Usually this happens when you go out on the track, and begin pushing your tires too soon. They haven't had a chance to heat up all the way through, and the chunking begins. It usually takes 3-5 easy laps at 75-80% of the pace you normally run to heat them up, depending on the tire."