Bike tech explained

Your quickfire guide to bike jargon

Kamm-tail tubes

● The Kamm tail (truncated tail, named after German aerodynamicist Wunibald Kamm) “cheats” the air into believing that the tail is still there, providing less air resistance than a round tube, and that means more speed for the same efforts.

Reach

● The horizontal distance between the centre of the bottom bracket to the centre of the head-tube. A longer reach lowers your ride position, a shorter reach means you sit more upright.

Stack

● The vertical distance between the top of the head-tube to the centre of the bottom bracket. A taller stack means a more upright ride position; lower stack means a lower (racier) position.

Trail

● The trail figure is derived from a combination of headtube angle and the fork offset. This measure shows the tyre’s contact point ‘trailing’ behind the steering axis. A small measure of trail makes for a fasthandling bike; more trail slows down the steering response.

Ultegra Di2

● Shimano’s new generation Di2 (digital integrated intelligence) brings wireless communication from the shifters to the derailleurs for the first time. The derailleurs work from a battery mounted inside the seat tube wired to both. New Ultegra Di2 has also become 12 speed which means it’s compatible with both pro-level DuraAce Di2 and the new 105 Di2, though you can’t upgrade from a mechanical 11-speed set-up without changing every groupset part.

Investment casting

● The term “invested” means “surrounded” in this context. Investment casting uses a shell made of ceramic, plaster or plastic that’s formed around a wax pattern. The wax pattern is then melted and removed in a furnace and metal is poured into the shell to create the casting.

Hydroforming

● Hydroforming uses pressurised liquid to shape and stretch a tube into the desired form, reducing the need for welding, and increasing strength.