Bad weather and price-cutting by rivals have hit demand for bikes at Halfords (LON:HFD), sending its shares freewheeling downhill.
Halfords said greater levels of discounting as well as poor weather deterring casual cyclists had caused an 11% decline in bike sales in the second quarter to date.
The group forecast worse-than-expected cycling sales for the quarter as a whole, but said trading in all other product areas stayed robust.
Car maintenance sales in the eight weeks to August 28 rose 7.3%, with a particularly good performance by car parts.
It plans a fightback in cycling including a complete overhaul of children's bikes and accessories, special offers and staff training.
"Looking further ahead, we have an exciting pipeline of innovation for bikes and accessories and we remain confident in the medium and long-term growth opportunities in the cycling market," Halfords said.
For the first half, management anticipates retail gross margin to be at the better end of the previous full year guidance range of -25 to -75 basis points year-on-year decline.
Management expects full-year group pre-tax profit to be broadly in line with prevailing market consensus.
Chief executive Jill McDonald said: "In my first three months at Halfords, I have reviewed all aspects of the group and it is clear to me that Halfords is a strong business with a well-balanced portfolio. This recent weakness in our cycling sales is disappointing, but it comes after two years of very strong growth in the category and has been partly offset by strong growth in both car maintenance and car enhancement sales."
Shares in Halfords fell 48.7p or nearly 10% to 461.3p. Analyst Keith Bowman at Hargreaves Lansdown said: "In short, the update raises questions over the group’s rollout of its Cycle Republic stores, with pressure on the new chief executive clearly rising.
"For now, and with analyst opinion having already fallen back from a buy to a cautious buy, a further downgrade looks inevitable."