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I have a singlespeed with a flipflop hub to change to fixed gear. In my freewheel sprocket I have 16 teeth and in the ring chain 46 teeth.

For me this is almost always the perfect combination for touring where I live.

But sometimes I want to go up a mountain (15-17% ) and I,m not strong enough to keep pedaling. I,d like to have the fixie side as backup for those occasions with more teeth.

I don't have any local shop to try gear ratios so I have t guess and buy.

Is there any method to guess how many more teeth do I need considering what I already have? I can go around 15km/h in a 7%hill.

  • This probably depends on your body strength, weight and height. Maybe there is a ratio conversion but I don't know it. Good Luck. – William May 12 '18 at 17:53
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    Fixed gears and mountains don't really mix. – ojs May 12 '18 at 19:04
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    You're OK so long as the teeth in your upper jaw match the teeth in your lower jaw, so you don't hurt yourself when you grit your teeth while climbing. – Daniel R Hicks May 12 '18 at 21:01
  • Could you fit two singlespeed freehubs instead of having a fixed side? A fixed speed on a hill would be terrible for going down any downslope because your wheel will drive your feet. – Criggie May 12 '18 at 22:48
  • Borrow a derailleur bike with a 46 tooth front chainring, and ride it up this hill. Find a gear that feels right to you, then count the teeth. If you can't get exactly that chainring size do it anyway, and get the ratio of rear teeth to front teeth, and calculate the required rear teeth with 46 front. At the end you will have to make an educated guess. – Criggie May 12 '18 at 22:54
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I don't think you can do it unless you are planning on carrying a few chain links to splice in whenever you flip your wheel. In any case, with the relatively large 46 tooth chain ring I think you'd need at least 36 teeth on the back to get up a 15% grade. Which would require a chain with 10 more links

  • Good point. OP may need a chain tensioner, or set the chain length with trackends so its long on the small cog (ie axle is aft) and short on the bigger cog (so axle is near the front of the adjustment.) – Criggie May 12 '18 at 22:50
  • No problem to have two master links, and carry a bit of extra chain. (And my multitool has a chainbreaker as well). Back when I were a yoof, and toured on a 3 speed, I carried a bigger rear sprocket, and a bit of chain. I could change it before climbing across the ranges, and again at the top for the speed down. (it was mostly to get more speed going down). We used to carry a spare master link in the puncture kit, as they sometimes lost the clip. – Henry Crun May 13 '18 at 10:13
  • Thanks, I didn't take that into consideration. I don't think is worth it then.. How many more teeths can I have without needig a longer chain? – nck May 13 '18 at 10:50

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