A tyre needs two things: the wheel size (ISO bead seat — "700c", "29" and "28" are the same 622 mm) and a frame that clears its width. We check width against the frame maximum the manufacturer publishes; when no maximum is on file the verdict is "unknown".
- How do I know whether a part in this category fits my bike?
- Every part page lists the standards it requires and its computed verdict on each bike in the fleet, with its confidence and sources. An "unknown" verdict means we do not have the measurement on file — not that it fits.