Bike size and FAQ

Bike sizing is about aligning two windows relevant to cycling and position:

1. Rider Window

2. Bicycle Window

For a good size/fitting both windows need to have an overlap. The greater the overlap the better the size and the more ability there is to tune the bike fit, technique and performance.

The smaller the overlap the more limitations there are with attaining a good or optimal fitting for comfort or performance.


1. Rider Window

The rider window relates to the range of positions a rider can comfortably achieve and sustain while riding. The rider window is highly variable and constantly changes either through correct training or following injury or time off the bike. Correct technique and conditioning increases the Rider window allowing more performance orientated positions and less fatigue and general muscular and joint discomfort. Injuries or time off the bike reduces the rider window.

Sitting Technique

Sitting technique has a huge impact on dynamic sizing (sizing to the bike, not sizing from a height chart). During our sizings we teach riders how to correctly sit, aligning their hips and spine for better function, alignment and rduce injury risks. Correct sitting tecnique is the first and most important step in sizing and fitting. We teach this as the first step in our sizing process.

Pedal Technique

Pedalling technique has an significant effect on the rider window. By teaching this, a dramatic effect on biomechanical alignment and Rider Window can be achieved almost immediately. These should be a priority for riders with injuries or wnating to increase performance or training volume. We teach these in our Forward Motion Bike fitting.

Flexibility, Mobility and Strength

Changes in flexibility, mobility and strength have significant effect on the rider window. These are of equal importance and can be trained with our specific Forward Motion exercise and pilates programs. 


2. Bicycle window

For any given bicycle frame, there is a window of adjustability that can be achieved by adjusting or changing different components. By adjusting or changing components, the position the rider is placed in will change.

Standard components on your bike which can be adjusted  include:

Stem spacers (handle bar height)

Stem position (high or low to adjust handle bar height)

Shift/brake lever type and position

Handle bar angle

Seat height

Seat position

Seat angle


The window can be further increased or changed by changing the components:

Stem length and angle (shorter or longer, higher or lower)

Handle bar width and shape (narrower or wider, deeper or shallow bend)

Crank length (shorter or longer)

Pedal width (wider or narrower)

Saddle (shape, width, cutout)


Sizing - The window of overlap and FAQ

How to chose a bike size?

Choose a bicycle frame size where the Rider Window aligns/overlaps to the Bicycle Window as much as possible. We can help you with this.

The larger the windows are of each and the more they overlay the better the fit outcome and the more ability you have to accommodate changes as the Rider Window changes.

A setup where the rider is outside of the Rider window means they typically have a reduction in performance, comfort and sustainability.

Can I ride more than one size of bike?

The Bike Window often overlaps across two or more sizes, meaning a rider can ride two bike sizes of the same model without any concerns and achieve a good fit.

There will be differences in how the frame sizes respond on the road (handling) and the choice comes down to preferences in riding style and future needs or changes over time where one may be better than the other. Ie what are the furture windows of overlap that may be required.


If I can ride more than one size, which one should I choose?

Choose the size that has the most overlap if you are considering all future needs and where the bike does not require extreme modification for you to ride in your comfortable position.

Where the Rider Window and the Bike Window have a small overlap, the bike may not be the best choice as the position window will be limited and may not accommodate future needs that arise.

Choose the size that has more overlap in your "performance window"if you are a competitive athlete. As a rider chases more performance they will push towards the outer edges of the bike window.