BikeDynamics - Bike Fitting Specialists

BikeDynamics - Bike Fitting Specialists

Bike Fitting Guidelines - Rules of Thumb

Knee Angle - Maximum

Ideally the knee should extend to between 145° and 150° at maximum extension. Often an attempt to open the knee angle by raising the saddle will just open up the ankle joint instead. If set too high, the hips will rock, causing lower back pain and saddle sores.

See Saddle Position and Crank Arm Length

Knee Angle Minimum

Once the maximum knee angle has been established, the minimum should be checked. Avoid an angle less than 70° as this can put high shear forces into the knee joint, exaggerates the 'dead zone' at the top of the pedal stroke and can cause discomfort in the hip and lower back. If too tight, you will need shorter crank arms.

See Saddle Position and Crank Arm Length

Saddle set back

The simplest method for establishing saddle fore aft position is to hang a plumb line from the tibial tuberosity (the bony bump below your kneecap). This should pass straight through the pedal spindle when the crank arm is at three o'clock.

See Saddle Position

Torso Angle - Fast

Torso angle is very dependent upon the cyclists choice of performance and comfort. A lower position is more aerodynamic as frontal surface area is reduced. 30° to 40° is a good compromise of performance and comfort but does rely on reasonably good flexibility to lower back and hamstrings.

Torso Angle - Touring

A more relaxed torso angle will take the pressure off the lower back, hamstrings and the neck and distribute loads from hands to seat. 40° to 50° is a suitable angle for longer distances where comfort is the priority over speed.

Torso Angle - Very Fast

A torso angle of <30° prioritises performance over comfort. Unless a rider has a very flexible lower back and hamstrings it is unlikely that this angle could be sustained without moving the saddle forward to open up the hip angle.

Upper arm and elbow

Irrespective of torso angle, the upper arm should always be between 80° and 90° to the upper body. This puts the shoulder in a relatively stable position and distributes loads directly into your skeleton. If ever fitting a shorter stem, care should be taken to check that knees do not hit the bars when riding out of the saddle.

A small bend in the elbows will help dissipate road induced shock load into your upper body. If you feel you need to ride with locked elbows, you are probably too far away from the bars.

Hand Position

Dropped handlebars are designed to offer a number of holds to facilitate both alternative torso angles and a variety of hand positions. This is to suit different road conditions and prevent discomfort due to staying in one position for too long. Once saddle height and set back has been established, stem length should be set such that the hands fall naturally to the hoods. This offers the alternatives of a more relaxed position up on the bars and a more aerodynamic position on the drops. If riders spend nearly all their time up on the bar tops, either their top tube or their stem is too long for them. The hoods should be adjusted such that the wrists are straight (as when shaking hands).

See Handlebars

Cleat Position

The cleats should be positioned such that the ball of the foot is over the pedal spindle and to accommodate the natural toe in or out of the foot. The ball of the foot can be defined as the end of the first three metatarsals bones which can be found with a bit of light prodding. Alternatively just use the bony lump on the inside of the foot at the base of the big toe.

See Foot to Pedal

For more details please use the following links.

Muscle Activation around the Stroke	Length Tension Relationship
Foot to Pedal	Varus Valgus Angles Cleat Alignment Foot to Pedal spindle Longitudinal Arch Support Pronation and Supination Coupling of Dorsiflexion with Foot Inversion
Saddle Position	Saddle Height - Knee Angles Saddle set back - KOPS, CofG and Pelvic Tilt
Handlebars	Reach - Torso, Upper Arm, Elbow and Wrist angles Handlebar Width
Crank Arm Lengths	Recommendations Hip and Knee angles
Temporary Riding Positions	Climbing Ankling Honking On the Drops On the Rivet
Time Trial/Triathlon Positions	TT Geometry Biomechanics Aerodynamics Comfort
Hips, Knees and Ankles	Typical Knee Displacements Ankle Behaviours

BikeDynamics Bibliography

You may be interested in some of the contents of the BikeDynamics library.

We say : If you are going to buy one book on Bike Fitting and the implications to injury, comfort and performance - this is the one.	We say : The latest scientific knowledge in a range of subjects from Biomechanics to Nutrition.	We say : Full of formulae and graphs. One for the Engineers.
We say : Good anatomical summary but also very strong on suitable weight training workouts.	We say : Excellent training recommendations but also good sections on bike handling skills and flexibility.	We say : A celebration of cycling technology. Good for those scared off by graphs and formulae.
We say : 'The' text book on conditioning, road cycling biomechanics, nutrition, hydration and trauma.	We say : A practical guide to the human body without being too "clinical".	We say : A clear, simple and inexpensive reference.

Page Last Updated : 24th August 2010

BikeDynamics - Bike Fitting Specialists