Long stem does not mean steep geometry. It could be due to a bike fit choice. E.g.. Lets take a Giant Anthem. Small has a TT of 57.5cm, the medium has a TT of 59.5. I need a top tube including stem measurement of around 66-67 cm. DO I take a Small and fit a 90 or 100 mm stem and have a shorter wheelbase that's a hoot around tight singletrack climbs or do a I take a Medium with a 70-80mm stem but 2cm longer wheelbase? More stable on descents but not going to go uphill as quickly, not goin to be as stiff and its going to be heavier. depending on my preference for where I need the bike to work with me more, will determine which size I opt for rather than a paradigm of short stem + wide bars = mountain biker and Long stem + narrower bars = Dirt roadie. In this case I'd be more inclined (Excuse the pun) to opt for the small for marathon and the medium size on something like a Trance. reason being about how the bike is going to be used most of the time.
