A 36 spoke 29er bike wheel is a rare thing. While a 36 spoke wheel is not a new idea, they have been primarily used for BMX bikes, which have smaller diameters. When using larger 29 inch wheels, there is some debate as to whether a 36 spoke design is better than the standard 32.
Most people agree that a 36 spoke 29er bike wheel is generally stronger than a 32 spoke design. However, they tend to be heavier as well, which is a disadvantage in some minds. The fact that they’re harder to find also helps contribute to their unpopularity.
A 36 spoke 29er bike wheel is often avoided by professional cyclists because they are not as aerodynamic as are the standard 32 spoke wheels. Fewer spokes means less drag, which translates to more efficiency. In fact, there are a few companies that are experimenting with using fewer than 32 spokes to further help the aerodynamics.