Examples
Examples
Try the starting example
- Saddle reference height above BB (mm)
- 700
- Straight seat-axis angle above rearward horizontal (degrees)
- 75
- Horizontal rail adjustment forward (mm)
- 10
- Existing reference setback behind BB (mm)
- 160
- Saddle reference x, forward of BB (mm)
- -177.564435
- Setback behind BB (mm)
- 177.564435
- Straight BB-to-saddle reference distance (mm)
- 722.169737
- Setback change from existing reference (mm)
- 17.564435
Try another scenario
- Saddle reference height above BB (mm)
- 700
- Straight seat-axis angle above rearward horizontal (degrees)
- 75
- Horizontal rail adjustment forward (mm)
- 20
- Existing reference setback behind BB (mm)
- 160
- Saddle reference x, forward of BB (mm)
- -167.564435
- Setback behind BB (mm)
- 167.564435
- Straight BB-to-saddle reference distance (mm)
- 719.776243
- Setback change from existing reference (mm)
- 7.564435
Calculation method
Calculation method
Saddle reference x, forward of BB (mm)
x=−height/tan(seat-axis angle)+horizontal rail adjustment.
Setback behind BB (mm)
−x; negative means the reference lies ahead of BB.
Straight BB-to-saddle reference distance (mm)
sqrt(x²+height²).
Setback change from existing reference (mm)
Calculated setback−entered existing setback.
Symbols and units
- a
- Saddle reference height above BB (mm)
- b
- Straight seat-axis angle above rearward horizontal (degrees)
- c
- Horizontal rail adjustment forward (mm)
- d
- Existing reference setback behind BB (mm)
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions & limits
Assumptions & limits
- A straight seat-axis side-view model with explicitly horizontal rail adjustment. It does not infer effective seat angle for a curved frame or recommend a saddle position.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.
Further reading
OpenStax: Euclidean geometry and trigonometric identities ↗
Background reading; this does not imply endorsement or independent review of SumFizz.