[JimboJames1972]

Chunking:

Usually caused by one of several factors - snagging your shell, hitting something, over-softening the tire rubber or excessive loading through the corners.

On the whole, tires with larger diameter side walls are more prone to chunking than smaller diameters.

Over-softening the rubber is something that many people over look. Each time you apply additive you soften the rubber compound. If you apply additive several times each meeting you run the risk of over-softening the tire rubber because its effect are cumulative. It also depends on what additive you use. CS High Grip seems to be the most aggressive on the rubber compounds (but some say it also gives the most grip) while Nosram/LRP carpet additives seem to be the mildest on your rubber. Jack the Grippa is somewhere in the middle.

A common method to reduce both tire wear and the chunking risk is to run multiple sets of tires each meeting. I use 3 pairs of rears and run each set twice only each week (two lots of practice, three qualifiers and one final so six runs in total). I find that, on average, I wear approx 0.2mm off each pair each meeting. Some of the guys who run just the one set wear up to 1.5mm (or more!) off each meeting! Buying multiple sets costs more in the beginning but I get several months from my sets. I also handly ever chunk them, so they pay for themselves very quickly.

Another thing to make sure of is that your outer sidewall is well rounded off. A sharp edge can cause the tire to bend under itself and give you either grip roll or chunking.

In my experience, the Contact 32 or 35 tires are more prone to chunking than the Mardave Pink Mediums, especially if you glue and true your own donuts on the Mardave rims. The pink donuts come with one sidewall that is smooth and slightly toughened so have this on the outside. this, along with the lip on the rim of the Mardave tire will go a long way to help reduce the chunking risk.

Hope this helps,

James