Got curious. Found the following. My guess it may be correct. If I remember, I will check my BX 2200 today and report back if it is 5.5 inches or not.
Edit: ignore the text between this point and the edit below…
“Kubota BX series tractors are generally known to have the 4x100mm front wheel bolt pattern, but there are exceptions. Specifically, the early models in the BX series, such as the BX1500, BX1800, BX1830, and BX2200, have a different front wheel bolt pattern.
Kubota BX Models with Different Front Wheel Bolt Patterns:
1. BX1500: 5 x 139.7mm (5.5 inches)
2. BX1800: 5 x 139.7mm (5.5 inches)
3. BX1830: 5 x 139.7mm (5.5 inches)
4. BX2200: 5 x 139.7mm (5.5 inches) [BX22 AS WELL ?]
Most other models, particularly the newer ones, typically use the 4x100mm bolt pattern.”
Edit: Oh well, so much for trusting the Internet. The bolt circle on my BX2200 front wheels is 4 inches, which would be the same roughly as 100 mm. My measurement was with a tape measure so it could certainly be that the true measurement is 100 mm. But definitely not 5.5 inches!