What the fork?

[sooprvylyn]

I mean the sidecar is cool and all, but what is that fork situation?

[The Mighty Gryphon]

That's a leading link front suspension.  Used with sidecar rigs.  The geometry is different from telescopic forks to reduce the trail of the front wheel to make steering require less effort.

Because of the extra weight of the sidecar and the inability to lean into turns the sidecar rig needs more effort to steer.

[sooprvylyn]

Interesting. The more you know.  I don't know much about sidecar, but they were never offered by bmw for the k bikes right? Like they're aftermarket?

[Chaos]

K bikes were a popular choice for sidecars, not all have the leading link conversion but some had that and a subframe.  Can get pretty pricey to do it right.

[Laitch]

. . . but they were never offered by bmw for the k bikes right? Like they're aftermarket?

They're aftermarket.

[Laitch]

Here is a gallery containing some BMW sidecar offerings by sidecar manufacturer LBS. Check out the Kit section, too.