Bosch Performance CX Sprocket

[Trekkie]

I want to upgrade the front sprocket on my bike. It currently has a 15 tooth sprocket and bought a 20 tooth but it is too big as the motor casing has a moulding which I guess acts as a chain guide. Has anyone updated a Trek Powerfly front sprocket and what size did you go for?

Thanks

 

[soundwave]

sort of screwed on that one unless you can grind away the plastic with a dremmel ect.

or just remove the plastic case tho it might look kak with out it.

 

[Gadfly]

15 to 20 teeth is a huge change in gearing. You may well be happy with a 16 or 17 tooth sprocket which will likely fit straight on.

 

[Trekkie]

15 to 20 teeth is a huge change in gearing. You may well be happy with a 16 or 17 tooth sprocket which will likely fit straight on.

Hi Thanks for the response, yes it is a big jump but from what I had read the bike had a 17 tooth as standard, but that wasn't the case. I will try a 16 or 17 and see how I do.

Regards

 

[Trevormonty]

Hi Thanks for the response, yes it is a big jump but from what I had read the bike had a 17 tooth as standard, but that wasn't the case. I will try a 16 or 17 and see how I do.

Regards

Why do you need higher gearing, 15t should be good for 40kmh in top, well above 25kmh assist cutoff.

 

[Trekkie]

Why do you need higher gearing, 15t should be good for 40kmh in top, well above 25kmh assist cutoff.

I’m working with a friend who’s a track cyclist and we need to do some sessions where she is maintaining 48 kph.

 

[soundwave]

unless you have a dongle there is no way you will keep up with that.

 

[Trekkie]

unless you have a dongle there is no way you will keep up with that.

I do, I’m using a badass dongle to overcome the limit.

 

[soundwave]

then you want as big as you can go at the front but after 20t its not really worth it as tried a 25t and it was the worst thing ever.

i have 18t and 20t dual sprockets on my bike.
http://www.pedelecs.co.uk/forum/threads/bosch-20t-offset-2-5mm-£14-99.32335/