Fork Length
What is Fork Length (Axle-to-Crown and Length-on-Axis)
Two distinct methods exist for measuring the length of a bicycle fork:
Bike companies will often fail to clearly specify the method used to measure a fork in their geometry tables, so it may be necessary to check for an accompanying diagram. If it's unclear which method a bike company uses, select Fork Length: Unknown.
Why is it important?
A change in fork length, such as when replacing a damaged fork or changing from a rigid fork to suspension fork, will change several other attributes of a bike’s geometry. Establishing the fork length used when determining the initial geometry is important so that these changes can evaluated.
Fork Length types
Fork Length (Unknown)
Fork Length (Axle-to-Crown)
The more common method of specifying fork length on modern bikes, measured in a direct line from the fork crown to the axle. Length-on-Axis is the less common method of specifying fork length on modern bikes, measured from the fork crown to the axle along the steering/head tube axis.
Be aware that bike companies will often fail to clearly specify the method used to measure a fork in their geometry tables, so it may be necessary to check for an accompanying diagram. If it's unclear which method a bike company uses, select Fork Length: Unknown.
Fork Length (On Axis)
The less common method of specifying fork length on modern bikes, measured from the fork crown to the axle along the steering/head tube axis.
Be aware that bike companies will often fail to clearly specify the method used to measure a fork in their geometry tables, so it may be necessary to check for an accompanying diagram. If it's unclear which method a bike company uses, select Fork Length: Unknown.