The utility cyclist wrote: .... I started riding a flat bar racing bike that came with mounts for racks/guards in 2001, it had the geo of a racing bike, handled like a race bike in every respect but actually was easier to handle more situations.....
I don't quite understand how something could both 'handle the same' and be 'easier to handle' all at the same time, but that aside I would say it is unusual for a frameset that is designed
for flat bars to be built 'with race bike geometry'.
If they were mostly built this way then it would be easy to change handlebar shapes without upsetting the steering geometry. However IME this isn't very often the case.
The usual differences are that a modern frame designed for flat bars will tend to have
a) a longer top tube and
b) slightly more trail in the steering geometry
when compared with a frameset built for dropped bars. There are a few framesets that are primarily intended for dropped bar use but are built with high trail and you can change to flat bars on these frames without ending up with something that steers terribly (although it might well leave you with a very short riding position or a long stem). But if you take a low trail frameset (meant for dropped bars) and fit flat bars to it, you can easily end up with rather twitchy steering.
I think the difference in the steering (with handlebar shape) can arise from several possible sources, including
- that the tiller action is different (i.e. how far ahead of the steering axis the hands are placed)
- that the weight distribution is different (i.e. that the load on the front wheel is often less with flat bars in use)
- that the width of the handlebars is different (most flat bars are somewhat wider than most dropped bars, or at least are once you allow for where the hands are often placed on them).
You will note that none of the above things is guaranteed; i.e. they won't definitely occur with every rider/bike that changes handlebar shape. But you can see how you might end up thinking that you 'prefer one handlebar shape' when really you might have a frameset/bike that will only suit you
if it is fitted with a particular handlebar shape.
I use flat bars on my MTBs and on my utility bikes; I wouldn't necessarily expect to be comfy all day long on either type of bike and on the road if I can get a lower riding position I'd expect to be a fair bit faster on a longer run because of the improved aerodynamics. With a good dropped bar setup I can choose to sit up and pootle or get on it a bit more if I want to ride fast. If I had a different collection of framesets/bikes, maybe I'd end up with more flat bars and less drops fitted to them (or the other way round), but the geometry of my riding position and my framesets would make fitting flats (or drops) to many of them a pretty dumb idea.
An example; I've long hankered after a rigid MTB type machine but with dropped handlebars. Of the twenty or so MTBs that I've owned (and experimented with as more road-based touring machines with slick tyres etc) only a couple of them have had a geometry that is really in any way suited to having dropped bars fitted. The rest all have had top tubes that are simply too long, so drops can't be sensibly fitted at all, or only with a stem that is very short, thus giving insufficient tiller (for the weight distribution/trail).
So people get very excited about handlebar shape but IMHO it is about as relevant as arguing about whether apples or cherries are a better fruit to have in a dessert; there is a nutritional difference there for sure (and that can be important) but some folk will prefer one to another regardless and furthermore each will work differently when used in combination with other things.