Methodology & limitations
Understand what is calculated, what is entered, and what remains unknown.
Calculation rules
Use manufacturer stack and reach for the exact model year and size. Add headset top-cap height consistently to the spacer-stack input.
Convert the stem and spacer arrangement into handlebar-clamp coordinates relative to the bottom bracket. Compare those coordinates instead of nominal frame size.
Solve the inverse stem geometry while holding the candidate spacer height fixed. Check real component sizes and every manufacturer limit before making a change.
Limits that matter
A cockpit calculation cannot guarantee fit, comfort, safe component installation, or handling. Validate the setup with a qualified fitter or mechanic.
Examples, imports, and source evidence
Example records are illustrative and are not a current public database. CSV and JSON imports are processed locally. A source URL supplied by a user does not mean that the publisher or this tool has independently audited that record. Missing specifications remain unknown. Inspect source dates and revisions before acting.
Reproducible results
Export a JSON plan to preserve the inputs and method version. Table exports contain the complete result, not just the currently displayed page. The printable report includes all result rows. A saved plan stays on this browser until you delete it or clear browser storage. Calendar exports create a snapshot of dates, not continuously updated alerts.
Corrections and commercial independence
Report calculation issues through the linked public source repository using an anonymized reproducible example. Do not include private addresses, serial numbers, personnel records, financial statements, or license-restricted data in a public issue. Advertising cannot change calculations, compatibility warnings, organic order, or source interpretation.