Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of truck-trailer builder Wabash National (NYSE: WNC) careened off the road today, falling as much as 13.2% on tremendous volume before finding their way back to a loss about half as large.

So what: You can pin the blame on last night's second-quarter report. Sales jumped 91% year over year to $287 million, and the year-ago net loss of $0.72 per share turned into earnings of $0.05 per share. Unfortunately, analysts were expecting earnings about twice the reported size.

Now what: CEO Dick Giromini adamantly promised that coming quarters will make up for this miss, because this was just "a timing event." But investors have seen their shares decimated by 46% in 2011, while rivals Trinity Industries (NYSE: TRN) and Volvo (OTC: VOLVY) have done much better for themselves. Over the last 52 weeks, Wabash is the only stock in this trio to underperform the S&P 500 by a significant margin. If I were interested in this industry, I'd be running out of patience with Wabash, too.

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