Bike Fit¶
Having the right sized bicycle that fits in all the right places makes a huge difference to enjoyment and performance when cycling.
A poorly fitting bike can lead to discomfort, pain and even injury.
A bike fit will check your position of your whole body on your existing bicycle and make adjustments to avoid injury and improve cycling efficiency.
The bicycle is fitted to a trainer or bike fit harness so the rider can peddle the bike, allowing a holistic view of the rider in action.
Changes should be made in small increments and tested before making further changes. A rider may need time to adapt to changes, so follow-up consultations are be invaluable, especially if significant changes to rider position are identified.
A bike fit ensures the correct bicycle size
The frame is the most significant part of the bicycle to change, so its important to get the right size and geometry for the type of riding planned.
Manufacturers are continually evolving bicycle design. Although there are many 'standards', there is no standard 'size' of bike frame across the industry.
The angle of the seat tube, size of tubes in the frame and where the tubes connect together (the geometry) can vary significantly, afecting the size of frame required.
A mini-bike fit should be done for each make and model of bicycle under consideration.
Mini bike fit - New bicycle sizing
A mini bike fit covers the essentials to ensure that a bicycle is in the 'fit window', determining if the bicycle is appropriate for the rider.
- saddle height to ensure legs are not stretching or bending excessively
- saddle position and angle, ensuring correct body contact
- rider reach to handle bars and controls, ensure a comfortable position
- hand positions on handlebars, ensuring comfort remains in various positions
The 'Fit Window' means that adjustments can be made to the bicycle to create the 'ideal fit' for the rider.
The height and inside leg measurements of the rider are taken to help identify their bike fit window.
Frame Geometry¶
Essentially geometry terms
| Term | Description | Affect on Ride |
|---|---|---|
| Top Tube Length | Horizontal distance between the seat post and handlebars | Influence stretch & reach while riding. Longer = more aggressive position |
| Reach | Horizontal Distance from bottom bracket to top tube | Key factor determining how stretched rider is. Important for sizing |
| Stack | Vertical distance from the bottom bracket to the top tube | Higher stack creates a more upright posture; good for comfort and endurance |
| Head Tube Angle | Angle of front steering axis | Slack angle (small number) = stable at speed; steep angle = responsive handling |
| Seat Tube Angle | Angle of the seat tube in relation to the ground | Steep angles place rider forward for better power transfer, especially on climbs |
| Wheelbase | Distance between front and rear axles | Longer = more stability. Shorter = more agility and tighter turning |
Use reach and stack numbers to determine the correct frame size (over generic size names or seat tube length).
Peddles & Shoes¶
A bike fit always starts with the feet and peddles, as this is where the body drives the momentum of the bicycle.
The correct size riding shoe should ensure the foot is not pinched or squashed. Badly fitting shoes lead to pain, blisters and deformation of the toes.
A few shoe manufacturers offer more range in sizes:
- Lake shoes available in standard and wide sizes.
- Bont provides wide fit and custom options (different size for each foot, etc.).
Cycling shoes design comes from a history of optimising aero efficiently over comfort
Consider one or two sizes larger than your normal shoes or a specific wide fit shoe.
Ensure you try out shoes before purchase and break the shoes in before undertaking a significant ride.
Saddle¶
The three aspects that control the comfort and effectiveness when sitting on the bike are:
- Pitch
- Heigh
- Set Back
Changing one aspect of the saddle will affect the others, e.g. adjusting the 'Set Back' affects the saddle height.
Pitch¶
The top of the saddle should be level horizontally.
A saddle that drops at the front can push the rider onto the handlebars, placing more strain on the wrists, arms, shoulders and neck.
When a saddle has a raised (slightly curved) rear section, the saddle level should be measured from the front of the saddle until the curve.
Height¶
A quick gauge of saddle height is to place the heal of the cycling show on the peddle and sit on the saddle. The leg should be straight and the hips level on the saddle (the rider does not have to lean to one side to straighten the leg).
When clipped in, the leg should be just below level when the peddle is at the top of the stroke. The leg should still have a small bend when the peddle is at the bottom of the stroke.
Set Back¶
The position of your saddle in relation to the peddles (bottom bracket).
Moving the saddle back by 3 cm will typically increase the saddle height by 1 cm.
Handle bar¶
The most significant measurements of a handlebar are:
- width: inline with the riders shoulders
- reach: the riders hands should can reach controls from any position on the handlebars
Width¶
Width is measured from the center of each forward facing arm of the handlebars.
Sizes range between 360 mm (XS) to 420 mm (Large).
Reach¶
The measurement from the centre of the stem to the handlebar controls.
Handlebars may have slightly different reach, up to 3 cm between extra small and large handlebar sizes.
Shifter levers have an adjustable reach screw since 2010
Adjust the reach of the shift levers if they cause the hands to over stretch or otherwise feel uncomfortable, especially when the hands are on the drops of the handlebars.