Thursday morning's second quarter trading update from car and bike parts seller Halfords is likely to trigger full year earnings upgrades of around 8% or 9%, Singer Capital Markets reckons.Halfords' management said it expects to beat half-year consensus expectations of a pre-tax profit of £54.5m with a figure somewhere between £59m to £61m. Singer's estimate was ahead of consensus at £56.7m but below the new guidance range.Prior to Thursday's statement the consensus forecast for fiscal 2010 profit before tax was £97.3m 'and we would expect market expectations to nudge closer to a range of £104m-£105m on the back of this very solid start to the year, and on guidance that profit growth in H2 [the second half] is also likely' Singer said. Despite this, the broker is retaining its 'fair value' recommendation on the stock while its 275p target price, well below the current trading level, is under review.