Koba relies on semi-fat

The Swiss custom bike specialist Koba is at the forefront of offering bikes with the popular plus tire size. As early as July, Koba will be offering two fullies and a hardtail that roll off-road on 27.5 Plus tires.

"Two souls dwell, alas! in my breast", is not only the motto of Goethe's Faust, but will soon also be part of Koba's portfolio. The 29er bikes Big Sentiero, Carbon Sentiero and Big Racetool are equipped with the space in the rear triangle and fork to accommodate wheels in 27.5 Plus format.

Jan Koba describes the concept and defines the area of use: "With the voluminous 2.8-inch wide semi-fat tires, the rider has a lot of control. This is ideal for ambitious beginners. With a second 29er wheelset with tires of 2.1, 2.25 or 2.4 inches wide, the bike then becomes a cross-country bike and is ideal when ambitions and riding skills have increased."

Koba employee Werner Niessen explains: "You can ride the 2.8 tires with up to 0.8 bar tire pressure, which offers a lot of comfort. Difficult surfaces such as gravel lose their terror. With the semi-fat tires on the 100 millimetre Sentiero fully, you get that full all-mountain, even freeride feeling."

Three semi-fat bikes on offer
The 100 millimeter fullies 29 Big Sentiero and 29 Carbon Sentiero can be equipped with the 27.5 Plus wheels - or Semi Fat as Koba calls it. The 29 Big Racetool hardtail rounds off the Plus format range.

No Boost installation dimensions for the time being
The rear triangle of these bikes features 142 millimetre mounting dimensions, while the forks have 100x15 millimetre axles - i.e. no Boost formats in 148 and 110 millimetre widths. Jan Koba is very clear about the new axle standard: "The Boost format is ideal for 29er bikes, and the slacker spoking angle provides up to 15 percent more stiffness. For the 2016 season, however, we are still relying on the familiar installation dimensions for the time being."

Photos: Rims not as in series
The bike shown here is provisionally fitted with 650b FlowEx rims from Notubes. The Flow EX can take on the 2.8 tires from WTB, but with an inner width of 25.5 millimeters, the extra-wide tires result in a profile that is too round and tends to buckle under hard riding conditions. Wider rims from WTB (see picture above) are fitted as standard. Koba is currently carrying out intensive testing on Lake Garda and in its home territory of the Rhine Valley to determine the optimum rim width for the semi-fat tyres, which are likely to be WTB rims with a width of 40 millimetres.