OTTO Tuning System review

Make your gears ’appy

Our rating 
3.5 out of 5 star rating 3.5
GBP £37.00 RRP | USD $50.00
OTTO’s app is very user-friendly with clear, repeatable verbal and visual instructions that are easy to follow

Our review

The system delivers what it promises, so long as you comply with its compatibility caveats
Buy if, Calibrating your gears gives you the fear
Pros: Consistent results, effective app
Cons: No good for Campy-riding Android users
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If you find gear adjustment on a par with witchcraft and nuclear physics, OTTO’s Tuning System could be for you. At the time of writing, it’s compatible with most Shimano and SRAM 9-11-speed drivetrains. It won’t work with Campagnolo, Android phones or clutch rear derailleurs on current single ring systems.


The apparent phone-brand prejudice – it only works with iPhone 5 or 6 – is down to the front-facing camera the app uses to ‘see’ the gauge targets. The process relies on consistency and accurate calibration, so it’s essential to use the same hardware, and these iPhones share the same front cameras. Android phones are developed by different companies, and their cameras all vary, as do the iPhone’s more powerful rear cameras. Theoretically it is possible to support every phone camera, but the costs involved are prohibitive, and for now, this situation is unlikely to change.

Using the system also requires good lighting – sufficient to comfortably read a book – so allowing the Photogrammetry function to read the targets in much the same way as face-recognition software does in modern cameras.

The plastic gauges have 12 rear-facing targets, whose positions are scanned at the factory, and stored within the unique QR code on each box. The free phone app reads the code, and calibrates your camera and gauges to measure 3D positional differences between the rear derailleur and cassette of less than 1000th of an inch.

After creating profiles within the app for each bike you intend to adjust, you’re ready to start. Slip the orange gauge over the upper jockey wheel, and the blue one between the frame and cassette, then align both sets of targets as near to parallel as possible. 

Your options are to Check or Tune rear derailleur alignment. Checking is free and takes under a minute, whereas a complete Tune incurs an in-app cost per quarter (90 days £7.99/$11.99) or year (£19.99/$26.99), to cover current and future development.

A Check results in an accuracy index score plus corrective barrel adjuster tweaks, and can tell if your derailleur or hanger are bent. The target score is within 0.125mm of perfect, and as 11-speed chains are only 0.4mm from the next sprocket, setup needs to be precise. 

Tuning can be Fast, using only the barrel adjuster, or Complete, where you’ll reset cable tension and mech limit screws. Di2 and eTap systems can be checked, but not tuned.

We found the system foolproof, with consistent results when following the instructions. For most riders, using the free Check function, and adjusting as necessary will be sufficient, unless you’re starting from scratch and need walking through every setup stage. 


It’s light and portable, so easy to pack for travel, when derailleur alignment could be affected, and offers peace of mind for the less technically-savvy. It does have quite narrow appeal given that it’s not universally compatible with drivetrains and phones alike, but is innovative and just a little magical.

Product Specifications


Name Tuning System
Brand OTTO

Description Rear Derailleur Adjustment system