This conversion changes a 2 x 10 gearset to a 1 x 10. By using the 42T rear gear, it matches the range of gears you would normally have in a 2 x 10 setup. This mod reduces a fair bit of weight, as the front mech, shifter, cable and double chainrings are removed.
You require an 11-36T cassette to start with so that the jump to the bottom gear is not too great. The narrow wide chainring works really well and retains the chain by its profile alone. To assist retention, they recommend that you use this setup with a plus type derailleur with the added chain tension.
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