I want to install a chain catcher, but it is unclear what size I need for my bike. My seat tube is tapered, but still perfectly round, and has a radius of around 114mm. If my elementary school math is still clear, that means a diameter of around 36.3mm.

Both the Deda Dog Fang and N-Gear Jump Stop are available with a maximum radius of 34.9mm. Did I measure wrong? Is my bike weird? My seatpost size is 31.6mm. If my bike does indeed have a larger than normal seat tube (it seems normal to me), would a 34.9 size chain catcher work?