In the days of old, the Shimano freehub body standard was universally used in most hubs (we are not counting Campagnolo; after all, this is a mountain bike magazine). SRAM’s XD driver threw that standard out the window with a new design that accommodates a 10 tooth cog. No more interchangeability between SRAM and Shimano 11-speed mountain cassettes or even your favorite purple anodized singlespeed cog.
Problem Solvers has done what it does best, solve problems in the most simplistic way. The Zinger may be the only singlespeed conversion kit for an XD driver. It utilizes a six-bolt disc pattern for the cog interface and comes with an 18 and 20 tooth cog and spacers to help find that perfect chain line. This limits cog selection to Problem Solvers’ range of 16-22 tooth six-bolt cogs, or whatever TomiCOG you have left over from your ill-advised off-road-fixie days.
I mounted the Problem Solvers Zinger on a wheelset and put it to the test all through last winter. Installation was a breeze. First, thread the six-bolt carrier onto the XD driver spline and slide on the appropriate spacers and cog. Tighten everything using the six T25 bolts. Once those are set, you use a standard cassette lockring tool to tighten the carrier down. A very simple process, which took minutes, but my singlespeed ways found it bothersome having to tighten six bolts to mount it. I know. I am a simple man, and wrenching on six is five too many.
This may not be a commonly sought after product, and I don’t see any single speeders ditching their Shimano freehub body just to run a Zinger. At 133 grams with the 20 tooth cog this is likely not going to end up shaving any weight, even with the lighter XD driver. Nevertheless, the Zinger is a convenient and inexpensive option for either those that buy a used wheelset with an XD driver installed or those that have multiple wheelsets or multiple bikes and want to be able to mix and match between them, quickly and easily. For example, a rider that switched to a singlespeed drivetrain in the winter but uses a SRAM 1×11 or 1×12 for the rest of the year, a quick swap to the Zinger and a shorter chain could be accomplished in a few minutes with a minimum of tools.
This is a well designed and executed product for a select group of riders. I probably don’t need to tell you who you are.