I get asked a lot from my female clients that come to me for a fitting before they buy a bike (which is the right way to do it -- get a professional sizing done first, THEN buy a new bike and complete the fitting process on it) wondering which "womens specific" bike they should get.
First let me say that, certainly there are many ladies out there that are quite comfortable on their womens specific bike; and they can work out great. But in general, the idea that women need different geometry is a myth.
Let's start by looking at it from an industry standpoint. What are the major bike manufacturers doing? They seem to go one of two ways:
1. They take the men's line of bikes, eliminating the sizes over 57cm, stick narrow handlebars, 170mm cranks, a softer seat, and accent the paint with pink or purple.
A good example of this is Cannondale:
Compare the "like-sized" bikes and you'll find no difference whatsoever in their geometry; same effective top tube, head tube, angles, standover, etc. They use narrower handlebars, presumably a shorter stem or straighter (non-setback) seatpost because they tout a shorter cockpit length, and shorter cranks. (Also girlie colors.)
2. Others do all of the above and then shorten the top tube (and possibly lengthen the head tube).
The truth is that some women do well with option number 1 and others do well with option number 2 .......
........but so do most men.
Taking the 2nd option, where they actually change the length of a few tubes on the bike, assumes that relative to their height women have shorter torsos and/or shorter arms (and possibly less flexibility). While many women do have shorter torsos (and therefore are long legged) their numbers do not outnumber their more proportionate or long-torsoed breathren in great enough numbers to warrant a change in all their bike geometry, I think. Even if you accept that long-legged, short-torsoed women represent the center of the bell curve and have that large of a representation, then changes that the bike companies make to design a "woman's" bike are often not different enough to accommodate the women who actually need it -- on the order of a 1 - 2 centimeter shorter top tube and possibly 1 - 1.5 cm longer on the head tube.
Incidentally, this is the approach that Specialized, Look, Cervelo, among many others take when designing a "higher handlebar position bike" or one they tout to be used in Paris-Roubaix. These are designed for men and women. So it's good that they make these changes, but often I don't think they are completely filling the market niches -- which is why when I build so many custom bikes for people who don't fit these niches.
So I know, now it sounds like that first I was complaining that they make the changes at all and then I complain that they need to make even greater changes. But that's what I think they should do....
.....but they should do the same thing for the men's bikes as well. They should have two or three *grades* of sizing from more aggressive to more relaxed.
Some companies are doing this to a small degree, but, again, usually the changes don't go far enough. Or the more relaxed geometries available are built like Bradley Fighting Vehicles and don't come in a performance package at all. I don't think it's wrong for people to want to ride their bikes hard and have nice components and wheels WHILE being comfortable. Our cycling population is getting older, but a lot of these riders still want to compete or at least continue doing big rides.
So I'm okay with companies NOT changing the geometry specifically for their women's bikes. I'm also okay with them changing the geometry -- it just doesn't need to be "womens specific." Even riders with Y chromosomes need geometry adjustment to optimize their fit.
As long as the stock bike manufacturers continue to err on the side of producing bike geometry with a racing-inspired pedigree, this will continue to be an issue. Unfortunately many cyclists will be sold a bike that does not match their riding strengths, simply because it is all that is available.
Custom bike manufacturers (like Seven Cycles) should continue to benefit from this oversight, especially as the cost of a stock bike and a custom bike continue to get closer and closer together. (Take a look at Seven's Gateway Program and then look at some of the cost of Specialized's Tarmac line, Trek's Madone, Cannondale's SuperSix -- many of those stock bikes get up close to $10,000 in their higher iterations!)
So when anyone (man or woman) is looking for a new bike, find out first what size bike you need and if any special considerations to the geometry of the bike ought to be made. There may be a stock option out there for you. If you think your current bike and fit are pretty good take a look at the setup -- if you have a threaded stem that is set to the "Minimum Insert" line or your stem is short length and/or high rise, then you might be in need of some additional adaptations to your bike geometry.
Why not just have the high rise or short stem on there (or the saddle slid all the way forward or backward on the rails for that matter)?
The problem with making these changes is that the handling of the bike is not built around these set-ups. These changes can work to make the bike fit better and be more comfortable, but they can also begin to affect the handling and the balance of the bike.
It's bad enough that the big stock manufacturers make forks with only 1 or 2 offsets and rakes to use on all their bikes -- from their 62cm down to their 49cm bikes.
(SIDE NOTE: Very small bikes and very big bikes should have forks with different offsets, but this costs money, so there are very limited options in forks out there and the big bike companies try to make up the difference with the head angles of the bikes. When doing this, one end of the spectrum -- either the big or the small -- will have compromised handling. Some of the companies, when listing the geometry for different sizes will even list some of the fork offsets and not list the others, saying they are "proprietary". Having used the Zin to log in the geometry and setup of my client's bikes -- which gives you fork rake and trail among many other measurements -- I can tell you that many times the rake of the fork is not different from the other listed sizes, the manufacturer just chooses to hide the fact that it is the same fork.)
So then when we change the handlebar height or seat fore-aft significantly on these bikes the handling and safety can sometimes suffer.
So do some research, go see a professional bike fitter that can help you find what will work best for you, and if you plan to spend more than $3000, don't discount a custom bike if it suits your needs better than the stock offerings.