SRAM Automatix 2-speed hub

New article about the SRAM Automatix two-speed hub. We have information on maintenance, choice among variant models, and how to adjust the speed at which it shifts automatically.

Exploded diagram of the SRAM Automatix hub

Exploded diagram of the SRAM Automatix hub

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2 Responses to SRAM Automatix 2-speed hub

  1. Neal says:

    Dear John,

    I’m thinking about purchasing this hub. But i want to use it on my single speed bike. It’s a retro Raleigh racebike. My current sprockets are 46/18 and that’s fine for normal riding but i live in Holland so the hills are most difficult.

    How can i calculate witch ratio i need tot have lighter with the hub and when it changes gear it will be something like 46/18.

    I have an SRAM automatix hub with a 19 and a 24 sprocket. So now i want to calculate which sprocket i need on the crank.

    Hopefully you can help me:)

    • John says:

      Hills are difficult in Holland? Well, not much though I do understand that there are hills in the southeast of the country. Even without hills though, having a lower gear for acceleration is helpful.

      You say 46/18 but do you mean in the high gear or the low gear? And what is the wheel size?

      Once you assemble this information, you can answer the question using http://sheldonbrown.com/gear-calc.html. If the 1:1 gear is not the one you want to be like a 46/18, then adjust the size of the chainwheel until the other gear, with the sprocket you will use, gives you the development you get with 1:1 gear and 46/18. The chainwheel is going to be larger in proportion to the size of the sprocket, but also will be in inverse proportion to the hub ratio.

      (new chainwheel size) = 46 * (your sprocket) / (hub ratio * 18)

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