We’ve had big-wheeled 29ers and  big-rubbered fat bikes all presented as literally the next big thing. Now from Surly comes the Krampus, combining – sort of – the two trends in one platform, which they’re calling 29+.

With three-inch-wide tyres, you might want to call it a 31er, but Surly obviously thinks there are enough wheel size designations around without throwing yet another into the mix.

So what’s 29+? It starts with a gert wide ‘Knard’ tyre, 3.0 inches across when mounted on Surly’s 50mm wide Rabbit Hole rims.

Unlike a fat bike, the 4130 steel frame of the Krampus uses standard 100mm front and 135mm rear dropouts, so you’ll have a huge choice of tyres. The bottom bracket is 73mm, with a plate style chainstay yoke for clearance.

Out back, the drop-outs are rear-opening with a gear hanger, so you can go singlespeed or multiple sprockets.

The single-wall Rabbit Hole rim is named after the weight-saving drillings and builds into a non-offset rear wheel for dishless strength.Claimed weight is 699 grams.

The key component is the new 3.0 width Knard tyre. This size, and the associated tooling to make it, is unique to Surly. As UK Surly bloke Pat Joscelyne puts it, “It’s a completely unique mould that Surly have had made. Everyone said it couldn’t be done,” because tyre manufacturers didn’t previously have tooling that would take the over-sized moulds. There will initially be two versions of the Knard, 27tpi wire bead and 120tpi folding with a claimed weight of 850g, and more tyres with different tread patterns will follow.

According to Pat, UK importer Ison Distribution hope to have frames, rims and tyres in early January 2013. As there’s nothing else unusual about the platform, that’s everything you’ll need to build a Krampus with your own parts selection.

If you prefer to just pull a bike out of a box, Ison will have complete bikes late March or early April.

Sizing follows the same pattern as Surly’s Karate Monkey – S, M, L and XL ‘t-shirt’ sizing, with the Krampus having the same standover as the Karate Monkey (hence the steeply sloping top tube). There’s no exact word yet on pricing, but Pat says complete bikes will cost a bit more than Surly’s £1399 Ogre 29er, because of the unique tyres.

In case you’re wondering about the name, Wikipedia says: “Krampus is a mythical creature recognized in Alpine countries. According to legend, Krampus accompanies Saint Nicholas during the Christmas season, warning and punishing bad children, in contrast to St. Nicholas, who gives gifts to good children. When the Krampus finds a particularly naughty child, it stuffs the child in its sack and carries the frightened child away to its lair, presumably to devour for its Christmas dinner.