Author Topic: Ebike drivetrain  (Read 951 times)

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Offline Max8194

Ebike drivetrain
« on: December 09, 2020, 12:36:09 pm »
I recently purchased an ebike and I want to upgrade the drivetrain. I'm wondering what would be the best for it. The makers claim it can reach 38mph. I'm thinking changing it to a single speed with large sprockets. Since it is power assisted I'm not worried about how hard it will be to pedal. The largest chainring I can find is 65t. Are you supposed to put a small one on the back are a big one to get the fastest speeds?

Offline HikeBikeCook

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Re: Ebike drivetrain
« Reply #1 on: December 10, 2020, 06:16:50 am »
First my disclaimer - I am not a bike mechanic and I know nothing about Ebikes, but I know conventional bikes. You should consult your local bike shop before making changes.

Typically faster speeds would be obtained by a larger front gear and a smaller back one. I run an Ultregra triple ring on my go-fast road bike and the typical big ring on those is 52 tooth. I rode with a bunch of guys running Dura Ace rigs and had trouble keeping up on the flats and discovered their big rings were 53 tooth, so I swapped mine out for the 53 and got more top end. I think the typical Dura Aca rear cluster is 11 tooth through 25 tooth - the smaller gear is your go-fast gear.

Probably the easier gear change is the front gear, but there are several things to consider. Before any change in the size of the gear and changing the number of gears you need to make sure that your derailleurs and your shifters are compatible for the change and you will most likely have to adjust your chain length if the change is very dramatic. I believe I got away with the single tooth increase in front with no changes. My rear derailleur is a 9 speed, so I need to stick to 9 speed clusters in back and the "throw" of the derailleur has to handle the chain slack when I drop from a 28 tooth (bigger ring for climbing) to an 11 tooth for go-fast. On the flip side, the chain needs to be long enough to make it around the 53 tooth in the front and the 28 tooth in back, which is technically not advised due to "cross-chaining" which puts lateral stress on the chain, but should be allowed for in my opinion.

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Offline TCS

Re: Ebike drivetrain
« Reply #2 on: December 10, 2020, 03:28:26 pm »
I recently purchased an ebike...The makers claim it can reach 38mph.

That's well beyond e-bike and even moped territory.  Everywhere in Europe and the USA, a two-wheeled machine that can reach those speeds under power is a motorcycle.   ;)
"My name is Pither.  I am at present on a cycling tour of the North Cornwall area taking in Bude and..."