Marylin Monroe is rather unknown as a bike expert, and probably rightly so. Nevertheless, she has sung a song that summarises a hundred years of experience in frame construction. It's called "Diamonds are a girl's best friend". The diamond frame, commonly known as the "men's frame", is simply the superior construction in terms of its technical properties when it comes to the ratio of stiffness to weight.
The age-old design is so good that it is not even fundamentally challenged by high-tech materials: When carbon emerged in bicycle construction, many expected completely new spatial structures and liberation from tubular construction. But even the lightest and fastest racing bikes still have diamond frames. And this also applies to the competition bikes that women ride. Only when women are categorised as "ladies" do they sometimes ride "ladies' frames".
Every bike that falls into this category is characterised by a lower step-through than a diamond frame, i.e. the top tube hits the seat tube so far down that you don't have to swing your leg around the back of the saddle and pannier rack when getting on, but can lift your foot over the frame.
There are good reasons for this, even if they don't get in the way of skirts - which also apply to both men and women. Most trekking bikes have sloping top tubes for more freedom of movement when stationary. However, the "ladies' frame" is sometimes the better option with a heavily loaded pannier rack or child seat, if you are short or have limited mobility.
The variety of shapes has decreased drastically, as can be seen in the composition of our test: In the sportier market segment, the trapezoidal frame is offered almost exclusively, in which the straight top tube of the classic diamond frame simply butts a little lower against the seat tube. This frame shape is now also considered a "unisex frame".
The equally widespread "wave frame" of most step-through bikes is hardly suitable for sporty bikes and is therefore left out. The sporty shapes, where the French name alone exudes a certain elegance, have largely disappeared: the Mixte frame with two thin top tubes from the head tube to the rear dropout, the Meral frame with a half-height, curved top tube, the Anglais frame with a low-set top tube and two thin tubes from this junction to the rear dropout - such shapes are practically only built in steel. Our test bikes from Electra and Boettcher are therefore deliberately selected exotics in the realm of the unisex.
But what are the actual arguments against the lower step-through? It is the lower frame stiffness for the same weight, which noticeably impairs steering behaviour and riding safety on very light frames with a very low step-through. However, as our laboratory measurements (see right-hand side) showed, this loss can be easily overcome with aluminium trekking frames of average weight. All frames in the test proved to be uncritical in normal riding conditions.
The complete article was published in Trekkingbike issue 3/2016.
You can download the individual articles as PDF files here.
