You see, when going for a new stance on a Harley-Davidson by means of new wheels, shops generally choose to pair a 21-inch front wheel with a 18-inch rear one. We've seen that happening over and over again, so we generally know what to expect on this front.
What Thunderbike did though with this ride was move the 21-inch wheel that usually goes at the front to the rear. A move (and an effect) so rare it's bound to catch the eye. Also, the piece installed at the back is 260 mm wide, and held in place by a single-sided swingarm, so the effect is even more impressive.
To keep the usual ratio between the front and rear wheels, the one at the front is now 23 inches in size, and has a width half the size the one at the back, namely 130 mm. Both are part of the German custom garage's Big Speed series, and come in a five-spoke design. An air ride system helps the bike rise or get closer to the ground for a maximum visual impact, depending on needs.
Other than that, the crew says the "core of the bike is largely unchanged." The frame is stock, and so is the Milwaukee-Eight 114 engine it holds in its embrace. It does breathe though through a Dr. Jekill and Mr. Hyde exhaust system. Other elements, like the fenders, handlebar, or turn signals, are all aftermarket.
The bike is wrapped in a scarlet red livery that also gives it part of its name, Crimson Force. The second particle of the name is due to the fact the ride is part of Thunderbike's Force series (which also includes things like the Road Force and Red Force).
In all, close to 40 custom bits and pieces were fitted onto the Fat Boy. The German garage makes no mention of how much the entire project, man-hours and paint job included, is worth. For reference though, keep in mind a brand new bike of this kind is selling from the Harley shelves for just under $20,000, and the added bits alone amount to at least as much.