Shares in Halfords were under the weather on Tuesday, after UBS downgraded its forecasts for the car and bike parts retailer on the back of gross margin concerns."We downgrade or forecasts (-8%) and price target (-22%) based on our concern that continued weakness in consumer spending will put further pressure on Halfords' gross margin and like-for-like sales growth," the Swiss broker said.UBS said that I will struggle to turn more positive on the stock, until the gross margin stabilises.While a neutral rating is kept, the broker has scaled back its target price from 360p to 280p.By 12:01, shares were 3.25% down at 268.1p.BC