The US provider Otto Design Works is selling an iPhone app including a two-part measuring gauge for 36.99 British pounds, which can be used to adjust the gears. The gauge is placed on the pinion and cog and the app uses the iPhone camera to check whether the adjustment is correct. With the Otto Tuning System, the measuring accuracy is said to be just 0.125 millimeters.

According to the manufacturer, the system is compatible with almost all road bike drivetrains and almost all 2x mountain bike drivetrains from Sram and Shimano. Once the gauge has been set up correctly and the app has been used correctly, a computer voice from the smartphone provides instructions on which screws to turn and how to do so for the adjustment work.www.ottodesignworks.com