This is going to sound kind of stupid, but this has never happened before and I am not sure whether to blame the bike or the rider. The latter is a bit of a 'tard sometimes.
Anyway, I commute every day, and my main commuter has been very reliable. This evening, on the last turn onto my street, I am going about 20ish mph and in the middle of the turn I feel a distinct wobble. I take that corner every evening, and have never felt this before.
Being a block from home I just finish the ride. I check the bike and don't see anything strange, loose, worn, whatever.
The one thing significant today is that it was the hottest day of the year so far, but only three degrees or so hotter than earlier days this week and last week.
Anyway, ideas? Was it probably just a simple tire slip? Something mechanical I should check? Should the rider be mentally evaluated?