All of us at times has had a rider in our class that is not setup correctly. You’ve tried to approach them about their position (without cringing). Maybe their seat is way too low as if they were riding a BMX bike. Possibly their seat is too high as they appear to tip-toe through your class. Too far back….too far forward….handlebars too high. In most cases, riders welcome input on their position. But in some cases, riders are very reluctant to change, particularly those that have ridden a certain way for years. How do you get them to take your input and consider a different position? You don’t. Let Goni and Bob do it.
No, they are not heavy hitters in some organized crime syndicate, they are your personal bike setup consultants that no one can argue with.
First introduce them to Bob or Plumb Bob. Using a plumb bob attached to a string, you can not demonstrate proper knee alignment over the pedal axle (with the pedal at 3 0′clock). They may argue with you that their seat is not too far forward or backward, but they can’t argue with Bob (plumb bob). It is visual feedback that takes your “subjective” opinion and converts it to objective observation.
Usually, Bob is more than equiped to argue the point, but every once in a while we run into that very tough customer. They’ve seen the plumb bob trick (even though it is a real method of fore-aft measurement). Enter Goni.
Goni, or goniometer in formal settings, is a tool for measuring angles. Bob only has a string, but Goni has numbers, angle indicators and fancy lines and markers. Using a goniometer to check a riders knee angle at the bottom of the pedal stroke is very revealing. For the purpose of this blog post, I’m not going to go into detail on a proper range of flexion in the knee with the pedal at DBC (dead bottom center). There are a number of variables that we would need to consider including flexibility, injury and comfort in order to determine the appropriate saddle height for an individual rider. The point of this post is to use the goniometer as another means of visual feedback to blatantly illustrate the extremes.
For more information on bike setup and use of tools such as the goniometer and plumb bob, sign-up for one of our workshops.
NOTE: We actually don’t refer to our tools as “Goni” and “Bob”. However, feel free.
Do We Use a Plumb Bob and Goniometer in our Biomechanics Lab?
We do use various goniometers, but often substitute laser-guided measurements for the plumb bob. In addition to looking cooler, laser measurements are more accurate and flexible, allowing a bike fitter (or biomechanist) to observe compound angles and planes of movement simultaneously.
