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How does a small component company respond to Shimano's hollow crankarm technology? Rotor simply looked for their own way to achieve similar strength and weight benefits. Like Shimano, the Rotor 3D MTB Double Crank has hollow arms. Rotor's engineers achieved this with their Trinity Drilling System, a proprietary process that drills out the center of the aluminum crankarms after they've been extruded into shape. Three parallel bores are made into the length of each crankarm -- the center bore from the spindle end, and two outer bores from the pedal end, towards the spindle. Through this process, they are able to relieve the crankarms of excess material, and therefore excess weight, while maintaining the stiffness you want, and the strength you need.

This version uses a traditional 24mm steel spindle that is pressed into the drive side crankarm. On the left side, the crankarm attaches to the splined end of the spindle and is secured with a pinch bolt. All Rotor products including the 3D MTB crank meet stringent European safety standards, and what's more, have been tested under the Specialized Factory Race Team. Oh yeah, another guy rides with Rotor equipment who knows a bit about bike racing -- Ned "The Lung" Overend.

The Rotor 2 x 9 MTB system uses two chainrings and is designed for use with standard 9-speed equipment otherwise. What's the advantage you ask? As top level racers have known for a long time, there are many redundancies in gear ratios on a triple crank. And as their athletic level makes a granny ring unnecessary, why not take it off and optimize the two remaining chainrings to work in harmony, and give them what gear ratios they do actually need? It's a lighter, less complicated system than a triple crank and the Q factor is reduced to 163mm.

The Rotor 3D MTB Double Crank- Steel Spindle comes with an anodized black finish and is available in three crankarm lengths -- 170, 172.5, and 175mm. The alloy spider is compatible with all five-hole 110/74mm BCD chainrings. Chainrings are NOT included and may be purchase separately. It can be used with any 24mm external bearing bottom bracket system built to Shimano's specs. Claimed weight for the cranks only is 543 grams.

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