21in front wheel.

atomsplitter said:

With a mountain of cash that change is possible. The front end needs to be modified significantly to make it happen however. Whatever wheel you put between those or any forks won't just fit with the current brake calipers and ABS system. Also the radiator mounts may need modified to ensure the tire doesn't contact upon full collapse of the fork under load. It might be cheaper to just put a whole new front end on it including the triple tree.

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• Without a fender, it should clear just fine at full compression (only 0.8" additional radius).
• 6.2% more circumference might be pushing the limits of the amount of "error" ABS can handle. Though it would be less, relatively, since the rear wheel he added already has a slightly higher circumference than stock.
• Caliper and ABS fitment only matter in terms of the wheel's dimensions at their location. The center and spokes could easily be designed to use the stock parts in the stock locations and to clear the calipers. The rim and outer parts of the spokes could flare outward. From the image with the fender removed, there appears to be enough room for the added width between the forks. I presume he's already measured to confirm.
• It will require about 6% more braking force at the lever, though, to get the same deceleration.

sunny said:

looks like he is compensating for the oversized rear wheel he has? it looks like he has bigger rear tire at least from the photo

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