Already noticed by the specialized press: the new SF Deore 2019-2020
It is with great pride that Spherik presents its 2019-20 SF Deore.
Its quality of design and its competitive price make it an affordable and reliable machine that is very pleasant to drive.
Already noticed by the specialized press, it retains the characteristics that made it the “editorial choice” of VELOMAG newspaper for several years:
– Hydroformed alloy frame
– SHIMANO hydraulic brakes
– Single SPHERIK micro tray.
– SHIMANO deore 10-speed transmission
However, it differs from its predecessors by the choice of 80 mm wheels (27.5×4.5″) equipped with TERRENE CakeEater tires
What are the advantages of a 27.5″ x 4.5″ tire compared to a 26″ x 4.8″?
A) Ground contact analysis 27.5″ vs 26″
The fatbike is currently evolving towards the 27.5” wheel format, known to be “more rolling” and more efficient in traction, the upper diameter generating a longer contact surface with the ground. To verify this assertion, we compared three renowned 26-inch tires, in the 26 X 4.8 format, with the Terrene Cake Eater, which is fitted to all 2020 Spherik fatbikes.
The test was carried out with 80mm rims, a 75kg rider, at a pressure of 6 PSI.
The footprint left on the ground by the three 26-inch tires was similar within 2%, or 151 cm2. For its part, the Terrene Cake Eater 27.5 X 4.5 tire left a footprint of the same width, but much longer, for a surface of 286cm2, which represents a difference of 27%. Unlike regular tires, the Cake Eater has a thicker tread and softer sides, which allow the tread to flex flat, much like a car tire, to leave a mark on the ground as wide as a a 4.8 inch tire.
The Terrene Cake Eater is therefore a formidable winter tire, with aggressive lugs and a traction surface 27% greater than the best 26-inch snow tires.
B) Inertia analysis and angle of attack 27.5″ vs 26″
The large diameter of the 27.5” wheels obviously has the advantages of a superior traction surface, but also those of greater momentum and a better angle of attack.
The angle of attack affects how easily a bike can get over obstacles. The larger the wheel, the greater this angle, and the easier it will be for the wheel to pass over an obstacle, because the latter, in proportion, becomes smaller. On the trail, this results in a smoother behavior of the bike, both uphill and downhill.
The higher mass of a large wheel may seem like a disadvantage in terms of static weight, when the bike is stationary and needs to start. Indeed, the heavier an object, the more difficult it is to set in motion – this is called inertia. On the other hand, once this object is moving, it will be more difficult to stop – this is called momentum, and this is what makes the difference on trails. The movement of the wheel generates a centripetal acceleration, which increases according to the speed of rotation, and gives a “going air” to the bike, which retains its speed much better.
