# Bosch cox small chainring



## justin70 (Sep 17, 2007)

Looking at Haibikes on sale the xduro models have the Bosch cx with 18 tooth chainring in front, in conjunction with up to 42 tooth gear in back. My question is, is this accurate? Because it seems like this would give extremely good low end gear range for climbing steeps, but would limit high end.


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## highroad 2 (Jan 24, 2017)

Justin
It’s just the opposite than you would think because the Bosch CX is geared such that for every full turn of the crank the chain ring turns 2-1/2 times so that the 18 tooth chainring is the equavalant of a 45 tooth chainring.
My Haibike was not rideable for my local terrain so I installed a 14 tooth chainring (equivalent to a 35t ) and a 48t EX1 cluster.
Most mountain bikes have 32t chainrings so even 35 is not low enough at times ( depending on how much assist) .
You can get 14t chainrings from Motostrano in the San Francisco Bay Area.


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## justin70 (Sep 17, 2007)

highroad 2 said:


> Justin
> It's just the opposite than you would think because the Bosch CX is geared such that for every full turn of the crank the chain ring turns 2-1/2 times so that the 18 tooth chainring is the equavalant of a 45 tooth chainring.
> My Haibike was not rideable for my local terrain so I installed a 14 tooth chainring (equivalent to a 35t ) and a 48t EX1 cluster.
> Most mountain bikes have 32t chainrings so even 35 is not low enough at times ( depending on how much assist) .
> You can get 14t chainrings from Motostrano in the San Francisco Bay Area.


Wow, I don't understand the lack of low geared ebikes. Don't people have hills where they ride? Even the yamaha-PW bikes with 2x chain rings, the small ring is still a 32...


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## highroad 2 (Jan 24, 2017)

I totally agree with you regarding not low enough gearing on the only 2 assisted bikes I have ridden.
The Levo and Haibike.
Guys with Levos have to do some grinding modifications to go from 32 to 30 chainrings and us Bosch CX assisted owners can only go down to 35 equivalent.
This discussion has already taken place but I still wish I could get into the head of a Bosch CX engineer to find out what he was thinking with a 1 to 2-1/2 internal gearing.
Even a 1 to 2 ratio would be an improvement.
I ride moto trails which often have steeper sections than mountain bike trails


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