BikeCAD and the rigid fork: what each dimension in the dialog measures
BikeCAD's rigid fork dialog describes the fork with letters: A is the outer width at the shoulders, C the distance from the crown race to the crown, L the length parallel to the head tube, R the offset, and so on up to W. If you design in BikeCAD or receive one of its files, this table tells you what each one measures.
BikeCAD fork dimensions: what each letter measures
| Letter | What it measures in BikeCAD |
|---|---|
| A | Outer width at the shoulders |
| B | Crown depth at the top |
| C | Crown race → crown |
| D | Crown race seat diameter |
| E | Crown height at the level of A |
| F | Height from the end of the upper bend to the race |
| G | Crown thickness (top → lower arch) |
| H | Flat zone under the crown |
| J | Blade width in front view |
| K | Axle → brake hole |
| L | Length parallel to the head tube |
| AC | Axle-to-crown, direct |
| R | Offset (rake) |
| T | Blade tip width at the dropout |
| W | Fore-aft blade width at the end of F |
A, E, J and G describe the shoulder in front view; F, W and T, the blade in side view. To see how these dimensions fit into a fork design, read the guide to unicrown fork design.
L and AC: two ways to give the length
BikeCAD lets you choose how to give the fork length: L, parallel to the head tube, or AC, the direct distance from the axle to the crown. They are linked through the offset R: L = √(AC² − R²). Before passing a measurement to another program or to the workshop, check which of the two your design uses. The difference between them is covered in the guide to fork axle-to-crown length.
Opening a BikeCAD design in ForkCAD
ForkCAD opens .bcad files with the "Import .bcad" button. After importing, review the dimensions and define the blade bend before generating the drawing.
FAQ
What is dimension G in BikeCAD's fork dialog?
The crown thickness: from the top down to the lower arch.
What is the difference between L and AC in BikeCAD?
L is measured parallel to the head tube and AC in a straight line from the axle to the crown. With the offset R, L = √(AC² − R²).
What does dimension F measure?
The height from the end of the blade's upper bend, where the transition from the crown ends, to the crown race.
Can I open a BikeCAD file in ForkCAD?
Yes, with "Import .bcad". Review the dimensions after importing.
Sources
- BikeCAD, rigid fork dialog.