The Monkey Lab: Rohloff-Equipped, Belt Driven Spot Rocker SS 29'er Mountain Bike

This steel Spot 29'er was built for a customer in Lynchburg, VA. The customer came to us looking for a bike with a Rohloff SPEEDHUB 500/14 and a Gates Carbon Drive belt system. These two products offer the high durability, low maintenance setup he was after for a high-mileage off road bike. After considering some stock titanium options as well as custom options in steel and titanium, he decided that this mostly stock steel frame offered the right combination of weight, ride quality, and affordability. Saving some money on the frame left a little more for the component package, which is made up of top quality parts.

For the wheels, we laced the Rohloff rear hub and a Chris King ISO disc front hub into a pair of No Tubes rims using Sapim double-butted and brass nipples. This gave a relatively light wheelset without being too delicate. The customer is fairly light, so we went with No Tubes lightest front rim, the Crest. Since the rear wheel sees more weight and impact, we used an Arch EX rim in the back, which has the same shape as the Crest but with thicker side walls. Race spokes are the standard double butted option from Sapim and were chosen for their combination of weight vs stiffness. Brass nipples were chosen for their strength and corrosion resistance.

The Rocker SS is Spot's steel hardtail mtb frame. The geometry is optimized for predictable single-track handling and all-day ride comfort. You get the lively, comfortable ride you expect from steel in a frame that is lighter than many other steel frames. Owing to the steep, technical Rocky Mountain trails in the backyard of the Spot facility, the head angle is about 2 degrees slacker on the Rocker SS than on your typical 29'er frame. This gives the bike more stability on steeper descents and at higher speeds compared to typical 29'er hardtails, which are often designed around XC racing.

At the time this frame was built, we were able to request slight customization in the form of Rohloff-specific cable guides instead of derailleur cable guides. This, along with the Rohloff-specific dropout that Spot designed for their sliding dropouts, gives a clean, integrated look for the SPEEDHUB 500/14. Unfortunately, with a shift to offshore manufacturing, customization is no longer an option directly from Spot. We can, however, have one of their current frames modified by one of the quality frame builders we work with to achieve a similar result. The alternative would be to use zip-ties to attach the shift cables to the frame as we do on most builds when using an off-the shelf frame.

Build details