In March 2014 I attended a one day course on bike fitting and the use of the computer aided bicycle design software BikeCad which appears to be the market leader. I was unsure as to whether I wanted to purchase this without seeing it in action first as the online version would not run properly on my computer and in any case is limited in function. The idea of the course from a bike builder’s perspective is to learn how to fit a person to a bike and then transfer that information into the BikeCad program to design a perfectly fitted bike.
There are many fitting techniques and the Bicycle Academy course is taught by Tony Corke who incorporates many of the systems in use but maybe uses his own unique methods and insight. The bike fit takes place on the usual fitting jig and starts of with saddle set back, height and reach, these being the mainstays of the fit and subsequent bike design.
Tony, initially, completely ignores the geometry of the bike fit jig and merely adjusts the seat set back, reach and saddle and handlebar height to the point at which your body weight is just tipping forward from neutral as experienced with your feet turning the pedals and hands held behind your back. Saddle height is essentially determined by the sensation in the legs as the saddle is adjusted up and down. Obviously observing the rider on the bike for posture is a critical part of the process so doing it yourself is more difficult. The fitting process can be taken to the maximum should you desire by using your own pedals, cleats, saddle, handlebars and brake levers, all of which affect the fit if you are to be millimetre perfect. Some cyclists may even benefit from foot wedges or insoles to correct postural foot variations. For my purposes any adjustment of the jig to particular seat and head tube angles was irrelevant as we were then able to transfer the determined settings into the BikeCad program and fix them as invariable so they do not change as you experiment with different angles as you design your bike around these set parameters.
I found the BikeCad program not too difficult to use having been shown the basics but it does have a lot of variables and dimensions to input and is certainly not quick especially when starting off with inputting all the necessary data required. To get the most out of it you need to know pretty much all the equipment you will be using and it’s dimensions before you design the frame. It is however quicker to adjust the design once you have reached this point. Initially I am sure I could draw a diagram on paper much more quickly!
I did go on to begin to adjust my existing bikes to the dimensions arrived at (shown in diagram below). It requires finding the bottom bracket centreline from where all the measurements are taken. The bike has to be level and a laser spirit level is very helpful in finding the centreline. I am pleased that in my case differences from my existing bike set ups were small amounting to millimetres or the odd centimetre.
The main learning points for me were:
Think more carefully about seat set back before you buy your seat post.
Don’t stress about stem length, just use the dimensions to decide how long.
Ideally design your bike around your reach and leg length measurements so you will never be far away from a well fitting bike.
Of course there are some who will still say it’s a load of old cobblers.