Equipment rental firm Ashtead was making gains after JPMorgan Cazenove upgraded its rating for the stock from 'neutral' to 'overweight', saying that recent falls in the share price have been overdone.As of Monday's closing price, the stock had fallen by around 15% since hitting its all-time peak in July and the valuation now stands well below its historic average. The stock was up 3.12% to 648.64p by midday on Tuesday after the US bank said it sees "scope for further earnings upside to drive performance".JPMorgan said Ashtead's US business, Sunbelt, has continually "outpaced" the market over the past two years, delivering significant growth without any material pick-up in end markets."We believe that, as market conditions recover, the trend of larger players taking market share should continue allowing Sunbelt to continue this outperformance," it said.The bank said that a recovery in end markets could drive upgrades to current forecasts for the year ending April 2016 of between 21% and 41%.BC