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 car-parts retailer Advance Auto Parts (NYSE: AAP) rumbled to a 13.7% leap this morning, then quickly retreated to a still-impressive 9% gain -- all on heavy volume.

So what: The company just reported so-so sales but brilliant earnings in last night's second-quarter filings. Highlights included 2.5% same-store sales growth compared to the year-ago quarter and tight cost controls.

Now what: Free cash flows are declining due to a big rollout of 130 new stores over the past year. But you can't put the company down for expanding when it can be done with rising return on invested capital, which is exactly what Advance Auto Parts is doing. Shares are bouncing off a 52-week low here just like minor rival Pep Boys (NYSE: PBY), while industry giant AutoZone (NYSE: AZO) is climbing close to 52-week highs instead. Sure, AutoZone is a slightly more efficient operation, but Advance Auto Parts is getting better and growing faster. This looks like a great time to get into a big bounce play on the second-largest parts dealer.

Interested in more info on Advance Auto Parts? Add it to your watchlist.