Singlespeed 608 Slotted Chain Tensioner
A push-down chain tensioner for singlespeed conversions. It straps to any 12–25 mm chainstay through a 90° V-saddle and two 9 x 3 mm band slots that take zip ties or mini hose clamps, so dropout width doesn't matter. A 608 bearing (22 mm) runs on an M8 bolt through an 8.5 mm slot with 23 mm of travel, and two 5 mm cheeks with a 12 mm gap keep 1/8 in and 3/32 in chain on the roller. Shim the bearing to centre with M8 washers.
mechanism bicycle singlespeed chain-tensioner