Bike Sizing vs. Bike Fitting

The terms “bike fitting” and “bike sizing” can create significant confusion as they are often wrongfully used interchangeably. While they are very much related, they are two distinct parts of helping you match a bike to your body and riding needs. 

For those of you looking for the quickest possible answer to this question:

Bike Sizing = Selecting the appropriate size of bike (e.g. S, M, L,50cm, 52cm, 56cm, etc.)

Bike Fitting = Adjusting the touchpoints (e.g. saddle, handlebars, etc.) on a bike to meet a riders needs.

Bike Sizing vs Bike Fitting
Bike Sizing vs Bike Fitting

To help put this into perspective, we like to use the analogy of buying a suit (or other formal attire). Sizing is choosing the right size suit off the rack, and fitting is equivalent to having a tailor hem the trousers and jacket sleeves to match your body. Needless to say, if you pick the wrong size the tailor will have his work cut out for him (or the suit just may never fit)... skip the tailor and even the right size of suit may not fit quite right. 
If these answers haven’t quite satisfied you, read on as we dig a little deeper into bike fitting, sizing and how they relate to each other.

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What is Bike Sizing?

Bike sizing is the act of selecting the appropriate size bike to accommodate the ideal riding position for you, the rider. This is the first step in setting yourself up for success to ensure the bike you ride is well suited to your body and riding needs.  

Most people will be familiar with the most basic form of sizing, which is where a bike manufacturer provides a sizing chart for each model they make. This chart allows you to look up which size bike they recommend based on your height (and sometimes inseam). 

Bike sizing chart (Trek)
Bike sizing chart (Trek)

Now, there are several challenges and limitations with sizing a bike this way, which you can read all about in our post What is Wrong With Bike Sizing. However, the general principle of sizing is that you want to select a bike that will allow you to easily adjust it (aka fit it) to match the riding position that works best for you. This is commonly referred to as your target position, and is determined by a combination of your body dimensions, strength and mobility, riding goals, and preference.  

A mistake that many people make is to assume that because bikes are highly adjustable sizing isn’t that important. Of course you can just adjust the seat height to what you need, right? While it is true there is quite a bit of adjustability available on most bikes, choosing the wrong size can often make achieving your desired riding position challenging, expensive, or even impossible. 

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An often ignored part of the relationship between bike and rider is that every bike is designed with a range of rider positions (relative to the bike) where the bike will handle as intended. That is to say bikes are intended to have your weight distributed in a certain way, which is determined by your riding position. 

If you need to make significant adjustments (e.g. a much shorter/longer stem) to achieve your target riding position this changes your overall position relative to the bike. Though this may be an acceptable compromise for very casual riding, rides that involve more speed, distance, or technical handling are more likely to highlight the negative impacts this has on the overall riding experience. This is why choosing an appropriate size (and model) of bike for you and your riding is a critical first step to a great ride and setting you up for a great fit.   


What is Bike Fitting?

As briefly described in our intro, bike fitting is the process of adjusting the touchpoints (e.g. saddle, handlebars, etc) on a bike to meet a rider’s needs. While this may sound simple, there are actually more adjustments available on a bike than many riders consider, which can all play a role in your experience. Here is a list to get your started:

  • Pedals (q-factor/axle length)
  • Cleats  (lateral, fore-aft, rotation)
  • Cranks (q factor, length)
  • Saddle (shape, height, tilt, fore-aft)
  • Stem (height, angle, length)
  • Handlebars (shape, width, rotation)
  • Hoods and levers (angle, height, lateral position)  

What can be confusing for many about the concept of “bike fitting” is that fundamentally it spans a huge spectrum of activities. From something as simple as quickly adjusting the saddle height so you can hop on a bike and ride down the street, to spending hours/days/weeks with a professional fitter to dial in a riders optimal position for a world record attempt, these both broadly fall under the umbrella of fitting a bike. 

Get started on your fit with MyVeloFit’s FREE AI Bike Fit Check

Saddle position is a critical part of every bike fit
Saddle position is a critical part of every bike fit

More commonly bike fitting focuses on adjusting the bike to meet the biomechanical needs of a rider to help them be more comfortable, more efficient, and avoid injury. In our post on Balancing Goals in Bike Fit we identify five separate areas of goals rider’s can have that will impact the choices made during a fit. 

  • Comfort
  • Injury Prevention
  • Power Production
  • Handling
  • Aerodynamics  

Depending on a rider’s goals along with their physical needs will determine the level of effort and knowledge that might be required to help achieve a suitable riding position. It should be no surprise that the level of “bike fit” required to hop on a bike share bike and get to work is significantly less than the effort required for the athlete spending 15+ hrs training on their bike every week. This is also impacted by a rider’s “adaptability”, which is how easily their body compensates to be able to perform in different riding positions.   

This is why some riders can have great success simply applying a rule of thumb to set saddle height, while others will spend hours with a professional bike fitter over multiple sessions. More recently bike fitting apps like MyVeloFit have brought some of the technology and knowledge from professional bike fitting into a format that makes it easier for riders to undertake a high quality bike fit at home. This presents a great option for the majority of rider’s that would benefit from more detail than a simple rule of thumb, but don’t feel the need to invest hundreds of dollars in a professional fit.  

Get started on your fit with MyVeloFit’s FREE AI Bike Fit Check

How are Bike Fitting and Sizing Related?

Perhaps the most challenging part of the discussion around bike fitting and sizing is that they create a bit of a chicken and egg relationship. Finding the best size of bike requires knowing what position you want to ride in, so you can ensure the bike you buy can be adjusted to accommodate it. Seemingly you can’t find the bike you need without a fit, and you can’t very well fit a bike without a bike.  

For riders that are very confident in their existing riding position it can be relatively easy to compare their current fit coordinates to the future bikes you’re considering. If however, you’re not confident in your position, or perhaps for example you feel confident in your road bike position, but are interested in a mountain bike, it can be hard to get a good idea of what size might be best. 

This is why the gold standard of sizing processes is what’s often referred to as fit first sizing. This is traditionally an appointment carried out with a professional bike fitter and a full adjustable bike jig (often called a size cycle) which allows the fitter to help you find the ideal position based on your needs without the constraints of any single bicycle. Once your position is identified, the measurements can then be compared to a range of bike options to figure out which models and sizes best accommodate your position.  

A "size cycle" for fit first sizing
A "size cycle" for fit first sizing

More recently, this process has been made more accessible through products such as MyVeloFit’s Virtual Fit First Sizing. This allows riders to create a scan of their body and pose it on a variety of bikes in their desired position to help evaluate which bikes might fit best. This provides many of the benefits of a tradition fit first session, without the cost, travel, and time. 
Find the right size for you with MyVeloFit’s FREE Virtual Fit First Sizing

MyVeloFit's Virtual Fit First Sizing
MyVeloFit's Virtual Fit First Sizing

More About Sizing and Fitting?

If even this explainer hasn’t satiated your appetite for more information on bike sizing and fitting, we recommend checking out our Fit Academy Blog which houses many more detailed articles about both sizing and fitting. Stay up to date on the best practices and tips and tricks for creating the best riding experience possible.

Fit Academy Sizing Articles

Athletes from around the world use MyVeloFit to improve their cycling position. Whether you are a veteran or new to the sport, MyVeloFit can help you improve your position.

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