Bike Fitting vs Bike Sizing

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These two phrases are commonly found on the internet when we do a search on “bike fitting”. Are they any different from each other? What are the differences and how do we identify them?

The origin of bike fitting started many tens of years ago when bike builders first recognized the need for custom sized bike frames to suit cyclists of different tallness and body build.

As time progresses, custom sized frames turned into mass production models which complete with somewhat adjustable seatpost and stems to cater to mass market, allowing cyclists to pick and choose a bike size that “fits” better to their stature. This was when the first few basic bike fitting guidelines were born.

Although being known as bike fitting in the past, these methods of yesteryears have now been categorized differently under the term of Bike Sizing. The reason is that these procedures are still useful in helping a first-time bike buyer to determine which complete bike to buy right off the shelf, but it’s no longer sufficient to provide a personalized fit by modern bike fitting standards.

In the next few articles, we will take a look at a few common Bike Sizing methods and explore the reasons on why do they fall short in comparison to
a true modern Bike Fitting procedure.

 


Method-1

Start off with pedal at its lowest position. While seated on the saddle, place heel firmly on pedal and extend the seatpost upwards. Stop at the point when the knee is extended straight, that’s the height to set the saddle at.

Intention:
This method is meant to make sure the frame’s seat tube length is tall enough to support the maximum saddle height for that particular cyclist while keeping the seat post within its minimum insertion safety range. If seat post is extended beyond minimum insertion mark, this means the frame is too small and need a bigger frame size.

 


Method-2

While pedaling on a trainer, stop the leg at the lowest point of pedaling (6 o’clock position) and measure the knee angle to be between 135-145 degrees.

Intention:
With the knee angle placed within this statistical range, the risk of injury to the knees is lower. However simply putting the knee extension within this range does not guarantee a problem-free fit as the variation of 10 degrees is too great.

The two measuring methods above usually put the saddle in a position that causes discomfort at the groin, lower back and knees when cycling. Reason is that these procedures do not consider muscle strength and joint flexibility that affects the amount of leg extension when pedaling. Cyclist who is more flexible and stronger will naturally sit higher when compared to another who is weaker.

 


Bike Fitting

By not focusing on a “fixed knee angle” leg extension, bike fitting observes pedaling motion fluidity to determine saddle height. When a suitable leg extension is achieved, pedaling efficiency will be maximized without straining the knees and groin.

 


Chuah
Little Rock BikeFit Studio

As the first bike fitter in Malaysia to be certified by BikeFit.com & VelogicFit system, as well as classically trained as electrical engineer, his pragmatic approach in getting the best possible comfort out of a bicycle has allowed many customers to cycle further, better, faster and stronger. Not believing in standardized fitments to suit all cyclists,
he constantly researches and revises on methods of new and old to ensure customers get the best performance from their rides.

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