What kind of tread are you using exactly? Natural (gum) rubber seems to chunk more often than a synthetic replacement - so if you’re currently using gum rubber, I’d suggest upgrading to blue nitrile or possibly black SBR: http://www.mcmaster.com/#incline-conveyor-belts/=r17kv1
We had the same trouble last year with rubber conveyor belt treads on 4" AM performance wheels driven by 3 CIMs per side. That tread de-laminated frequently when we played defense – i.e., when we pushed robots.
This year we have switched to blue nitrile as recommended above. No issues during our Week 1 event. However, this year we have spent more time scoring, so less time playing defense, so far.
If you’d like something that has similar benefits to tread without having to deal with attaching the tread, we’ve really liked the Colsons that we are using this year. The main downside is that they require an interference fit hub (Meaning that you have to put the hub and the wheel into a vice and smash the hub in to a wheel)