Instruments

Not directly. HDI instruments are calibrated in km/h and can carry different pinout assignments for the neutral indicator and trip reset functions on some model years. The connectors look identical, but plugging an HDI speedo into a domestic wiring loom can produce incorrect speed readings and fault codes. If you're sourcing a used instrument from Europe, verify the part number ends with the correct market suffix before buying.

Yes. A tyre change that alters rolling circumference — switching from a 180/65 to a 180/55, for example — will cause the speedo to read high or low, which also affects the odometer and cruise control. Speedo healers (Trail Tech, Dakota Digital) splice into the speed sensor signal and let you dial in a correction factor. They're legal in the UK as a calibration tool; the offset lives in the device, not in the instrument.

Genuine H-D clusters carry a Harley holographic label on the PCB, visible through the back of the cluster, and a cast-in H-D logo on the internal housing. On a used unit, check the backlight uniformity — counterfeits usually show hot spots or uneven brightness. Cross-reference the part number etched on the back against Harley's microfiches; a number that doesn't appear in any fitment chart is a reliable warning sign.