In late August, Buffalo Wild Wings (NasdaqGS:BWLD - News) broke out of a cup-with-handle base in strong volume.

The base showed some accumulation. The handle had good action -- the lows drifted down in slow trade.

The fundamentals looked fairly strong. Earnings growth in the previous two quarters was 24% in the first quarter and 26% in Q2. Sales growth was 35% and 32%.

The drawback was Buffalo's 67 Relative Price Strength Rating the day before its breakout. The RS line was lagging too.

It may be tempting to ignore a low RS when other things look right. But research shows that the best stocks have strong relative strength when they break out.

Five days after the breakout, Buffalo Wild Wings slipped 7% below the 41.10 buy point. For many disciplined investors, this would have been sufficient reason to sell.

The 7% to 8% sell rule helps you preserve capital. Also, research shows that most big winners never drop that much from a buy point.

Buffalo rose about 9% above the ideal buy point after the 7% decline.

Then it fell, eventually shaping a base-on-base pattern. It's working on the seventh week of the base.

The RS Rating is 77 but could improve over time. It would also be nice to see the RS line act better.