Changing the front chainring on Bosch CX drive

[bikey850]

Hello,

Cube Bosch CX drive bikes appear to have a 15T front chainring. I can see that there are alternative third party versions available in quite a few sizes 16,17,18,19,20,22.

I am interested not to increase the motor asistance level or speed, but to make pedeling beyond cutoff a bit easier (less pedel RPMs).

Has anybody changed their front chainring, if so to what value, and what was the outcome like? Did you swap back to the original?

Did it affect your warranty? I can't image it would.

Also which brand Connex or FSA or does it not really matter?

Many thanks,

 

[RobF]

It's not clear what you are trying to achieve.

You say you want to make pedalling beyond the cut off easier, but also mention fewer pedal revolutions.

Generally, fewer pedal revolutions would equate to harder pedalling.

As a general point, changing the front ring on the motor is a simple job.

There can be motor clearance casing clearance problems if you go for a much bigger ring, but a couple of teeth one way or the other is almost bound to fit.

 

[Plodder Bob]

I swapped from 15 teeth to 20 teeth as I was predominantly using just the 4 smallest gears on the rear . The smallest 11 tooth rear sprocket was wearing quicker than the rest . Bare in mind most of my commute is reasonably level . I find I’m now rarely using the smallest gear at the back . I would say with a 20 tooth sprocket on the front there isn’t much clearance left between the chain and the Bosch cx casing . I prefer the 20 teeth set up can’t think of reason to swap back unless I develop a taste to go riding up some large hills - unlikely though ! My average speed has increased slightly but only by a couple of mph

 

[Plodder Bob]

Oh mine says Bosch on the sprocket don’t know how other manufacturers brands compare ?

 

[bikey850]

Hello,

Thank you both - sorry for the confusion, meant harder to pedel but with less RPM as I am spending the most amount of time in the smallest rear cogs.

Thanks for the suggestion of 20T - seems like a resonable value to try and had not thought about the clipping of the plastic surround on the Cube motor.

Thanks again,

 

[footpump]

I have bosch active line with 18t sprocket I find I tend to use the larger rear cogs to make it easier on my legs when peddling,
as I understand it the bosch front sprocket ratio is 2.5 so a 15t is 37t on a normal sized front chainring the 20t is 50t

 

[BazP]

Oh mine says Bosch on the sprocket don’t know how other manufacturers brands compare ?

The one on my Trek says FSA, the one on my Cube says nothing.
I have had three from E-Bike shop but they seem a bit flimsy compared to the FSA and with just a number on them. What or where you get an original Bosch one from I don't know, if indeed there is an original Bosch.

 

[KTM Bike Industries UK]

The one on my Trek says FSA, the one on my Cube says nothing.
I have had three from E-Bike shop but they seem a bit flimsy compared to the FSA and with just a number on them. What or where you get an original Bosch one from I don't know, if indeed there is an original Bosch.

Bosch don't make chainrings... they are all made by aftermarket made component brands, who supply the bike brands direct. When Bosch sell the motors they don't come with a chainring fitted.

A lot of them supplied on bikes are made by a company called Miranda.

 

[Plodder Bob]

Thanks all some good info given for anyone interested I bought mine from All Terrain Cycles seems good quality to me description = Bosch chain ring 20T part number 1270016205 paid £14.58 plus vat

 

[Trevormonty]

Also checkout Connex range of spockets.

 

[bikey850]

Hello,

Thanks for all the advice.

Ordered the increased front chainring - seems like worth doing and might help with the road perfomance at speeds over 15mph.

However, my Cube has a plasticy guard thing that sits just outside of the frontchainring.

When I fit a larger chainring it would be good to replace this to match the size.

Can you buy replacement ones of these with a larger size to match if the front chainring is increased to 20T?

Many thanks,

 

[Trevormonty]

Hello,

Thanks for all the advice.

Ordered the increased front chainring - seems like worth doing and might help with the road perfomance at speeds over 15mph.

However, my Cube has a plasticy guard thing that sits just outside of the frontchainring.

When I fit a larger chainring it would be good to replace this to match the size.

Can you buy replacement ones of these with a larger size to match if the front chainring is increased to 20T?

Many thanks,

Check miranda website, if anybody makes one it will be them.

 

[Plodder Bob]

I re-used the original one it looks ok offers partial protection

 

[Plodder Bob]

 

[bikey850]

Hello,

Thanks for the advice.

I think I might need some tools to remove the cranks and chainring.

Do I need the following items:

-crankpuller
-bosch spider tool to release the lock ring

Is it these parts?

https://www.bike-discount.de/en/buy/lifu-icetoolz-crank-puller-25941
https://www.bike-discount.de/en/buy/bosch-spider-tool-to-release-the-lock-ring-for-classic-plus-452280

Is a CX a classic plus?

Anything else needed, or links to a different (UK based) supplier?

Many thanks,

 

[Plodder Bob]

I just used a Halfords universal crank puller and a screw driver and hammer to knock the lock ring off . Bare in mind it’s a left hand thread so clockwise will loosen it . CX and classic are different motors not sure if the same spider tool fits both though ?

 

[Trevormonty]

Hello,

Thanks for the advice.

I think I might need some tools to remove the cranks and chainring.

Do I need the following items:

-crankpuller
-bosch spider tool to release the lock ring

Is it these parts?

https://www.bike-discount.de/en/buy/lifu-icetoolz-crank-puller-25941
https://www.bike-discount.de/en/buy/bosch-spider-tool-to-release-the-lock-ring-for-classic-plus-452280

Is a CX a classic plus?

Anything else needed, or links to a different (UK based) supplier?

Many thanks,

Get seal kit and gease while at it, plus spare oring. See attach parts list.

Also checkout Scooteretti recent youtube video on it.


View attachment Cube Stereo Hybrid 140 HPA Race 500 27.5 2016 bike parts.pdf

 

[bikey850]

Get seal kit and gease while at it, plus spare oring. See attach parts list.

Also checkout Scooteretti recent youtube video on it.


View attachment 23810

Hello,

Many thanks for the info - is that the same part used for a 2018 model? I'm guessing same motor so same part?

Also, do you know if thats the right Bosch spider tool (is a CX the same as as an classic plus? Make sense to order all the parts from the same place i guess.

Thanks again for everybodys help - much apprecaited.

 

[Trevormonty]

Hello,

Many thanks for the info - is that the same part used for a 2018 model? I'm guessing same motor so same part?

Also, do you know if thats the right Bosch spider tool (is a CX the same as as an classic plus? Make sense to order all the parts from the same place i guess.

Thanks again for everybodys help - much apprecaited.

Correct tool for CX and all Gen2 drives that use small chainring. CX and Performance haven't changed in 2018.

Bosch replaced Gen2 Activeline with new 2018 Gen3 direct drive Active & Active Plus ,which have large(normal size) chainrings.

 

[bikey850]

Hi,

Sorry - bit confused - which tool do I need to remove the lockring on a 2018 Performance CX motor?

1. https://www.bike-discount.de/en/buy/bosch-lockring-tool-for-locking-ring-assembly-active-performance-452266

or

2. https://www.bike-discount.de/en/buy/bosch-spider-tool-to-release-the-lock-ring-for-classic-plus-452280

Thanks in advance,