Halfords has pledged to step up its promotional activity after reporting a sharper drop in like-for-like sales over the past quarter.
Like-for-like sales dropped 6.3% in Q3, which followed a 4.5% drop in Q2.
However Halfords said it still expected to grow half-year profits by around 12% to between £67m and £69m.
Its decline included a 1.5% drop in sales at its Autocentres network, which is set to complete a rebrand from Nationwide Autocentres by next spring.
Halfords described the in-car technology market as very challenging and said its sales of sat-navs declined 16% in the first half on a like-for-like basis.
It reported low single digit like-for-like sales growth in its most profitable category of car maintenance.
The retailer's cycle sales declined although its camping equipment performance made a single digit increase.