Symptom, measurement, interpretation, change, validation.

The working sequence

1. Symptom: describe the reported behaviour without turning a feeling into a diagnosis.
2. Measurement: record the relevant value, unit, timing and conditions.
3. Interpretation: separate documented information from editorial assessment.
4. Controlled change: change one meaningful variable where the context allows.
5. Validation: compare the result against the original question and record what remains unknown.

Evidence and source hierarchy

Source material is kept distinct from evidence records. Manufacturer documentation, technical manuals, standards, academic papers and official data may support a statement, with source type and checked date recorded. Editorial assessment is labelled as interpretation, not measurement.

Context, assumptions and uncertainty

Applicability includes the vehicle, component, session or other relevant context. Assumptions are stated rather than hidden. Unknown, not measured and not confirmed are not silently converted to zero, certainty or a recommendation. When credible evidence conflicts, the conflict and its limits are described.

Quantities and conventions

• Displayed quantities carry an explicit value and unit.
• Conversions use a documented internal convention and avoid unjustified precision.
• Motion-ratio values explicitly state either the wheel-to-spring or spring-to-wheel convention.
• Review and update dates identify when changeable material was checked.
• Teaching or example data is visibly distinguished from measured real-world data.

Safety-critical context

For brakes, wheels, suspension, steering, restraints, structural components and tyres, this method does not replace manufacturer instructions, component documentation, physical inspection, event or scrutineering requirements, or qualified technical help where appropriate.

Guidance reference

ICO organisational guidance and WCAG 2.2 are reference points for the separate trust and accessibility foundations.