Nicolai's latest has clean lines

The G-Boxx unit from the right...

...and from the left. The final drive sprocket is concentric with the swingarm pivot, so there'll be no chain tension effects

Rear wheel can be removed without disturbing the disc, chain or sprocket

This is the Nicolai Nucleon TFR, or at least a pre-production example thereof. You're possibly wondering why the chain's on the wrong side and the derailleurs have all disappeared, but anyone familiar with other Nicolai bikes could probably hazard a guess. The German manufacturer has been building freeride and DH bikes with a centrally-mounted Rohloff hub gear acting as a gearbox for a while, an approach also used by Brooklyn Machine Works and a couple of other niche brands. But the TFR moves a step ahead. Rather than just a hub in the wrong place, it uses a G-Boxx.

G-Boxx is an initiative kick-started by the aforementioned brands to come up with a standard internally-geared, centrally-mounted unit that they can all share, rather than all coming up with their own slightly different ways of mounting a Rohloff in the frame. The G-Boxx unit is essentially the guts out of a Rohloff hub with a built-in primary drive replacing the external jackshaft/second chain arrangement that you'll have seen before.

But, you may be asking, what's the point of it? For a start, you get rid of all the derailleurs without losing any gear range, which is mud-friendly and low maintenance. You can get that benefit just by running a Rohloff, but they're pretty heavy beasts and sticking them at the back of the bike can make things a little strange-feeling. The G-Boxx puts all that weight in the middle where it won't do much harm. The system also neatly sidesteps the issue of chain-tension effects that exercise the minds of FS designers everywhere - the final drive is between two single sprockets so the chain alignment is always the same and the G-Boxx allows designers to put the final drive sprocket on the same axis as the swingarm pivot. You get a similar (but not perfect) effect with a regular transmission and a pivot around the bottom bracket, but the BB isn't necessarily the best place to pivot a swingarm. The Nucleon parks it a bit higher up, giving a bit of a rearward arc to the travel to fight bob and improve small-bump sensitivity.

The Nucleon TFR will be the first production all-round bike to use the system. The pre-production bike came in at 15.8kg (34.8lb) which isn't exactly svelte, but you do get up to six inches of travel and the weight distribution, with the heavy stuff in the middle and a very light rear wheel, should make it feel lighter to ride. We dare say production models may come in slightly lighter.

There's some cunning stuff going on at the back. Sliding dropouts deal with chain tension, while the custom rear hub carries the sprocket and disc on the same side - production bikes will have a shield between the two to keep chain lube off the rotor. The lack of a cassette means a dishless rear wheel, there's no freewheel mechanism - a common source of failure - at the back and some cunning patent-pending jiggery-pokery means that you can take the rear wheel out while leaving the disc and sprocket on the bike.

Production will start in the next couple of months. Importers Nicolai-UK will have one later in the year - supplies are likely to be extremely limited so if you're at all interested, get your name on the list. UK prices are unconfirmed but are likely to be nudging three grand for frame, G-Boxx, cranks and rear hub. Which sounds like a lot, but you don't have to add all that many bits to get to a complete bike...

You can talk to Nicolai and ride the other bikes in the range at the Mountain Mayhem demo day (Friday 25 June). See what else they've got to offer at www.nicolai-uk.com, or find out more about G-Boxx at www.g-boxx.org.