Other than the obvious marketing differences, such as in the colour of model, most of differences between bikes that are aimed at men and those that are aimed at women are not instantly recognizable just by a quick glance at a second hand bike.

The one exception to this is with the structure of the frame of the bike, however. A women’s bike is clearly identifiable because the top tube of the frame – the piece that connects the handlebars to the seat – is often slanted. The top tube is slanted downwards towards the seat of the women’s bike so that it is easier to get on the bike.
Not all second hand women’s bikes have this slanted design. Many models are available with the straight, parallel top tube that you will always see on men’s bikes. However, there are several other subtle – but important – differences in the design of second hand women’s bikes too. All of these are to take into consideration the different body type of the two genders.
As women usually have shorter torsos than men, the top tube of the frame will usually be a little bit shorter on used women’s bikes. There are also differences to be found in the shape of seat on women’s and men’s bikes. Men’s bike seats tend to be longer and narrower in design, whereas second hand women’s bikes tend to have a wider seat, which enables the pelvis to fit more comfortably around it. If you are not a serious cyclist and only use your bike for shorter distances, then a unisex seat would be fine. However, for longer distances and frequent use the women’s seat shape is a definite benefit to ensure a comfortable ride.
A common difference in body shape between men and women is in shoulder width. Women’s shoulders tend to be less wide than men’s. Therefore, handlebars on men’s bikes tend to wider than on women’s bikes. The usual width of handlebars on second hand women’s bikes is between 38 and 40cm. Men’s models tend to go up to 44cm. In the same way, because of the fact that women’s torsos tend to be shorter than men’s, the handlebar stem is usually shorter on used women’s bikes too.
A comfortable ride is obviously of paramount importance when choosing a bike. Body shapes differ, of course, and tall women are sometimes best suited to a men’s bike rather than a women’s bike. In general though, the differences between the two are tailored to the differences of the gender body types and are important in ensuring comfort.