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Geared Hub Allowable Input Sprocket Ratios

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  • Rich Wood
    Both Rohloff and Sram specify minimum input ratios for their gear hubs in order to limit the maximum torque peaks the hub internals are subjected to. Rohloff
    Message 1 of 3 , Oct 18, 2008
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      Both Rohloff and Sram specify minimum input ratios for their gear
      hubs in order to limit the maximum torque peaks the hub internals
      are subjected to.

      Rohloff lists a 2.35 ratio (38 tooth chainwheel and 16 tooth
      sprocket for example) for normal use. Their limit for tandem use,
      or for riders over 100 Kg in weight, is 2.5. This would be a 16/40
      combination. The manual is very specific about these limits on
      chainwheel/sprocket ratios.

      Sram lists limits for all of their gear hubs too. They are the
      following:

      iMotion9 1.73
      7 speed 1.83
      P5 1.8
      iMotion3 2.0

      The Dual Drive II, which uses a 3 speed hub and a 8 or 9 speed
      casette, recommends a 33 to 38 tooth front chainwheel. With the 9
      speed casette, 11-34 teeth, this allows for a input ratio as low as
      slightly below 1.0. Based on this the acceptable input torque for
      this hub is apparently very high. It is still not allowed for
      tandem or carrier bike use however. All this info is from the Sram
      gear hubs technical manual, downloadable from their web site.

      So far I have not found listed limits on input ratios for either
      Sunrace Sturmey Archer or Shimano gear hubs. I have emailed Sunrace
      asking about this and intend to do the same to Shimano. I will post
      results of my enquiries if and when received.

      Rich Wood
    • Rich Wood
      Per technical manuals from 1999 from the Sturmey Archer Heritage web site they listed the minimum acceptable input ratios on the two hubs checked as 2.0:1. As
      Message 2 of 3 , Oct 18, 2008
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        Per technical manuals from 1999 from the Sturmey Archer Heritage web
        site they listed the minimum acceptable input ratios on the two hubs
        checked as 2.0:1. As this is in the same range as the Sram data it
        is probably a good minimum to use for any gear hub except the
        Rohloff unless additional information is available.

        Rich Wood


        --- In Geared_hub_bikes@yahoogroups.com, "Rich Wood"
        <astronut1001@...> wrote:
        >
        > Both Rohloff and Sram specify minimum input ratios for their gear
        > hubs in order to limit the maximum torque peaks the hub internals
        > are subjected to.
        >
        > Rohloff lists a 2.35 ratio (38 tooth chainwheel and 16 tooth
        > sprocket for example) for normal use. Their limit for tandem use,
        > or for riders over 100 Kg in weight, is 2.5. This would be a
        16/40
        > combination. The manual is very specific about these limits on
        > chainwheel/sprocket ratios.
        >
        > Sram lists limits for all of their gear hubs too. They are the
        > following:
        >
        > iMotion9 1.73
        > 7 speed 1.83
        > P5 1.8
        > iMotion3 2.0
        >
        > The Dual Drive II, which uses a 3 speed hub and a 8 or 9 speed
        > casette, recommends a 33 to 38 tooth front chainwheel. With the 9
        > speed casette, 11-34 teeth, this allows for a input ratio as low
        as
        > slightly below 1.0. Based on this the acceptable input torque for
        > this hub is apparently very high. It is still not allowed for
        > tandem or carrier bike use however. All this info is from the
        Sram
        > gear hubs technical manual, downloadable from their web site.
        >
        > So far I have not found listed limits on input ratios for either
        > Sunrace Sturmey Archer or Shimano gear hubs. I have emailed
        Sunrace
        > asking about this and intend to do the same to Shimano. I will
        post
        > results of my enquiries if and when received.
        >
        > Rich Wood
        >
      • brandon
        I Agree Rich must be a exported hub and someone buys my hub decides he wants a easier ratio so the dealer finds a special sprocket and installs it. I was
        Message 3 of 3 , Oct 18, 2008
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          I Agree Rich must be a exported hub and someone buys my hub decides he
          wants a easier ratio so the dealer finds a special sprocket and
          installs it.

          I was talking to my friend who i bought it off and i found out that
          his brother found it at the tip and took it gave it to my friend after
          a couple of years then he sold it to me it originally came from
          lismore tip where i used to live and lismore is very hilly so it must
          have been bought for that reason.

          The local bike shop had no idea as where it was sold and there is only
          one bike shop left whereas before there was at least five around that
          period and nothing is left.

          Brandon.

          --- In Geared_hub_bikes@yahoogroups.com, "Rich Wood"
          <astronut1001@...> wrote:
          >
          > Per technical manuals from 1999 from the Sturmey Archer Heritage web
          > site they listed the minimum acceptable input ratios on the two hubs
          > checked as 2.0:1. As this is in the same range as the Sram data it
          > is probably a good minimum to use for any gear hub except the
          > Rohloff unless additional information is available.
          >
          > Rich Wood
          >
          >
          > --- In Geared_hub_bikes@yahoogroups.com, "Rich Wood"
          > <astronut1001@> wrote:
          > >
          > > Both Rohloff and Sram specify minimum input ratios for their gear
          > > hubs in order to limit the maximum torque peaks the hub internals
          > > are subjected to.
          > >
          > > Rohloff lists a 2.35 ratio (38 tooth chainwheel and 16 tooth
          > > sprocket for example) for normal use. Their limit for tandem use,
          > > or for riders over 100 Kg in weight, is 2.5. This would be a
          > 16/40
          > > combination. The manual is very specific about these limits on
          > > chainwheel/sprocket ratios.
          > >
          > > Sram lists limits for all of their gear hubs too. They are the
          > > following:
          > >
          > > iMotion9 1.73
          > > 7 speed 1.83
          > > P5 1.8
          > > iMotion3 2.0
          > >
          > > The Dual Drive II, which uses a 3 speed hub and a 8 or 9 speed
          > > casette, recommends a 33 to 38 tooth front chainwheel. With the 9
          > > speed casette, 11-34 teeth, this allows for a input ratio as low
          > as
          > > slightly below 1.0. Based on this the acceptable input torque for
          > > this hub is apparently very high. It is still not allowed for
          > > tandem or carrier bike use however. All this info is from the
          > Sram
          > > gear hubs technical manual, downloadable from their web site.
          > >
          > > So far I have not found listed limits on input ratios for either
          > > Sunrace Sturmey Archer or Shimano gear hubs. I have emailed
          > Sunrace
          > > asking about this and intend to do the same to Shimano. I will
          > post
          > > results of my enquiries if and when received.
          > >
          > > Rich Wood
          > >
          >
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