A sensible rationalisation of the fat bike phenomenon, this all-new Surly appears to win over everyone who throws a leg over it.
The company's long established Pugsley has been the bestseller of the fat-bike breed by bar. But, as with most models, its blimp-like tyres require other modified parts for clearances. Plus, there aren't many riders who'll be able to rationalise the use of 4in rubber on normal trails.
The Krampus is the rational alternative. It has a 29er frame and fork that can be fitted with either normal 29in wheels and tyres or Surly's 50mm Rabbit Hole rims and Knard 3in tyres. Our test bike came with the latter combination.
Ride & handling: Smooths out any trail
After two weeks of fairly intense riding we're happy to state that the 'better off fully grown' approach of 29in wheels with less tyre girth succeeds in seducing more riders than the obese treads of other fat bikes.
While it's no shock that 3in tyres grip tenaciously to almost anything and roll with buttery softness across rocks and roots, it is surprising that they roll so fast across the sort of terrain where we expected to feel much more drag.
The Krampus could be the bike that makes fat bikes acceptable to regular off-road riders, rather than niche groups who ride mainly on sand or snow. Okay, that might be unfairly stereotyping the majority of the current fat bike breed, but we've ridden quite a few of them and the Krampus is in a different league.
It's essentially a trail-tuned 29er with frame, fork and wheelbase room for tyres that measure about 31in from edge to edge. Run at between 15 and 20psi the Knard 3in tyres absorb all the little rocks, roots and ripples of the trail, and do so more effectively than a short travel fork or shock because they deform around stuff rather than telescopically compressing.
The result is a rolling chassis that stays steady in terms of handling and makes every trail feel much smoother and grippier. Comfort is superb and control is better than on a short travel full-susser because the long wheelbase (43.75in on our medium bike) is inherently stable, and the geometry isn't shifting slightly on every bump.
Our test bike came equipped with Surly's 50mm Rabbit Hole rims and Knard 3in tyres
While the fattest of the fat bikes focus on traction via floatation, the Knard tyres straight-line on a fairly narrow block knobbed centre tread and roll at pretty much the same speed as conventionally fat 29er tyres.
But the extra girth offers loads of extra grip, comfort and confidence when you start to bank the bike over on twisty singletrack, allowing you to carry your speed through corners to an extent that would become alarming on most other bikes.
Inevitably, you'll end up braking less as you gain confidence, and this lets you focus on maintaining the extra rolling momentum that comes with heavier rims and tyres. The rubber on our test sample weighed 1.15kg (2.54lb), a fair bit heavier than claimed, but the slotted rims are only slightly heavier than other 29er models.
You notice the extra drag in initial acceleration but soon seem to end up barrelling back up to the guy who just pulled away. We did a few freewheel downhill rolls for the sake of comparison with other 29er tyres, and the Krampus got further.
Frame & equipment: Tough steel with heaps of room for customisation
The frame is built with Surly's trademark tough 4130 CroMoly butted steel. All the tube junctures are reinforced for maximum durability, and adaptability is to the fore, with conventional hub spacing, well-placed rack mounts, two sets of bottle mounts, mudguard eyelets and horizontal dropouts that permit a geared or single sprocket setup.
There's masses of mud room, even around the Knard tyres, and the long top tube reach (24in on our medium bike) keeps the front tyre clear of your toes. You can buy a frame and fork package to equip as you wish, or score the complete bike with cable disc brakes and a Shimano SLX 1x10 drivetrain.
The 50mm rims and 3in tyres mean you can't run a triple crankset, but with a 36 sprocket at the back a double would winch you up almost anything. We were happy with the Salsa 34T single on our test bike.
Complete bike weight was 13.3kg (29.4lb) without pedals.