Insight: Frame Geometry ladies road bike

The last complete bike I built, was a ladies’ road bike for my wife.

There were a lot of peculiarities in this project:

  1. a very demanding “customer”
  2. a “customer” with very little experience in road bikes
  3. a lot of time for the fit
  4. very well known riding biases

The funniest fact might be, that it took me more than 3 years to finalise the geometry. This was mainly due to the fact that the framebuilding only started to late. But all that time gave me the opportunity to optimise my wife’s riding position on two other bikes until I felt very confident with the result. An that leads to the first finding:

Fit is the main priority.

The picture on top of this post was my first manual drawing. It was already a good fit regarding saddle-to-bar-position. That means: I had to find a solution to build a frame for only 6cm saddle elevation. That’s the main reason why I opted for a 6° sloping top tube and 1cm steerer tube ecxess. So I could achieve a nominal frame height of 55cm from where the top tube is lowered by 1cm and then descending at 6° towards the seat tube. That measures were found based on the inseam length, torso and arm lengths, known preferred saddle superelevation and my knowledge of her riding position.

Then the frame had to be really short due to my wife’s short torso length. It came out with a 52cm top tube at 73° seat tube angle. This was based on a strictly “Outside-in”-appproach starting at the saddle position. Based on saddle-bar-length I then considered the planned stem parameters (6° rise, 90mm length) and the conventional headset.

Different from most production frames, I could not cheat with super-steep seat tube angles, as the correct fit was my personal motivation. But usually short frames means toe overlap. So there is a big advantage for me building a “private” frame: I can accept some toe overlap. But in this case, I still wanted to avoid it. At the same time I knew very well how bad flat head tube angles can feel. So went for a moderate head tube angle of 72,5° and some more fork rake of 48mm to achieve my personal sweet spot trail of 55mm.

The result of all this is what I aimed for: A perfect fit frame for a person with shorter than normal torso AND a perfectly neutral-yet-lively road bike. The bike fits very well in all handlebar positions due to the moderate riding position and the compact handlebar.

A nice side-effect of the outside-in-engineering approach is surprisingly balanced visuals for a short and high road bike.

 

 

 

 

 

Insight: Frame Geometry ladies road bike