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.

Interested in more info on Wabash National? Add it to your watchlist.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.