(ShareCast News) - Group like-for-like sales at car parts and bikes retailer Halfords rose 0.3% in the third quarter with the company reporting that full year pre-tax profit expectations would be unchanged.Halfords added that full year retail gross margins would fall to -25 to -75 basis points, but that full year retail operating cost growth to be in the range of +1.0 - 2.0% against previous guidance of +2.5 - 3.5%. Group pre-tax profits were expected to be in the range of £78m-£82m.For the quarter, retail like-for-like sales were flat, while at the Autocentres division they rose 1.9%.In cycling, growth in sales of bikes and cycle repair more than offset a small decline in parts, accessories and clothing, while in motoring, car maintenance sales were impacted by the warm weather, partially offset by a strong performance in sales of wiper blades and bulbs, and continued growth in fitting services.Lower tyre prices offset increased service, maintenance and repair revenue at the group's Autocentres operation.Chief executive Jill McDonald said she was pleased with the group's performance, "given the unprecedented weather conditions"."Particularly pleasing was the strong growth in service-related sales and a return to like-for-like growth in cycling. We achieved a record day online over the Black Friday weekend, our highest ever day for total sales on 23 December and further improvements in customer service metrics. In Autocentres we achieved a 9 consecutive quarter of LFL growth," she said.