I have a 20" folding bike with a shimano Nexus Inter-3 (most probably this one), and I find that even on flat terrain (not to mention downhill) the 3rd gear is simply too slow: I often find myself cranking very fast exerting a very low torque, and 2nd gear is good for most slopes (<15%). I mainly use the bike for commuting, on mostly flat terrain.
My current top speed seems to be around 20-25 km/h, I would like to be able to do 40 km/h. That means an increase by a factor of two.
I am searching for a way to up the gear ratio, my options seem to be:
- Increase the size of the front chainring (45 currently):
- This would make folding harder.
- I would also need to change the chain protector and possibly the pedals.
- Decrease the size of the rear cog (18 currently):
- This would increase the strain on the individual cogs and increase the chance of slipping (that already happened) and chain fall-off.
- Change the gear hub to one with a higher upper ratio:
- May need to change the shifter and corresponding wiring
- May not fit in the current frame
- The current ratio is 1.360, I would like at least 1.8 or even 2.0
- I do not really need gears below 1.0, and certainly not below 0.73 (my current 1st gear). Unfortunately most gear hubs concentrate on the lower gear ratios, but I am yet to find a comprehensive table of available gear hubs (wikipedia's, and Sheldon Brown's have different flaws). Shimano's 4-speed hub seems promising, but is discontinued.
Which solution (or combination of them) do you recommend? If it is the third, what specific gear hub(s) do you recommend?