I did the PCC Sprint Clinic this past Saturday at VSC, and in my second match, the rider I was riding against lost his front wheel in turn 3. We weren't going very fast, around 16 or 17 (I was, anyway). He was above the sprinters line, and had made an abrupt "jink" with his handlebars, and down he went. Three people went down over the length of the session, and all did it for the same reason - too slow to make the kind of move they did. What kind of tires did they have? I don't know.

By the way, I misspoke. The 25MM tires on my training wheels are Tufos. They've been just fine! They're great at Hellyer, and they've been a non-issue at VSC.