this post was submitted on 11 Jun 2026
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Robust drive-trains for mid-drive e-bike conversion (lemmy.ml)
submitted 1 day ago by cvieira@lemmy.ml to c/bicycles@lemmy.ca
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Hello everyone!

After several years and thousands of miles of commuting by bike, I recently installed a mid-drive e-bike conversion kit on my gravel bike. For the most part, the experience has been absolutely fantastic. However, I'm having some pretty frustrating difficulties with the drive-train, and I've exhausted my expertise.

The bike came with Shimano Claris, which is certainly not the most robust drive-train. When I first installed the kit, the chain was skipping over the cassette pretty much any time the bike went under load. The cassette already had several thousand miles on it, so I replaced the entire drive-train (chain, cassette, and derailleur) with brand new Claris components. This worked great for about 200 miles (~4 days), but then the cassette started skipping again.

I replaced the cassette again and pretty much immediately snapped a chain. I again replaced the chain, and about 50 miles later snapped it again. I brought it to a local bike shop, that once again replaced the drive-train (this time with higher-end components) after noticing one of the cassette rings had been cracked down the middle. I brought it home, only to snap another chain within 50 miles, stranding me several miles from home.

Funnily enough the components are cheap enough that I'm still spending less than I would on gas/car maintenance, but obviously this is something I want resolve regardless.

I'm in the process of looking into more robust drive-train options. My priorities are durability and low maintenance cost/difficulty, but I don't care as much about weight/efficiency. I'm putting several times the power you'd typically put through a drive-train, so I'm not sure most of the go-to higher-end options for typical road cyclists would be sufficient.

I've seen some people discuss more exotic drive-trains like belt drives and internally geared hubs. Those sound intriguing, but also very complex to retrofit. It seems to me like there has to be some sort of drive-train with a larger/thicker cassette and chain, at the expense of having fewer gears. Perhaps something like a belt drive really is the safer option?

I'm willing to spend quite a bit on this, but I want to be confident it would actually be a reliable long term solution.

I appreciate your advice here,

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[–] FlyingWhales@lemmy.world 1 points 12 hours ago

My priorities are similar to yours, I ended up going with an internal gear hub on my mid drive. A Shimano Alfine 8, it was fairly expensive as I had to have a wheel built around it but after a thousand miles plus I don't regret it.

750w Bafang mid drive, mostly run in the mid power range but quite often loaded up with luggage.

I found this link useful: https://www.electricbike.com/mid-drive-kit-igh/

[–] JillyB@beehaw.org 1 points 1 day ago (1 children)

If you do want to go the belt-drive and igh route, you'll need to have your frame modified. You'll need to have a belt split added to the seat stay and the rear triangle modified for 135mm dropout spacing (probable you don't have 135mm dropouts). You would need the rear derailleur replaced with a belt tensioner.

Since you use drop-bars, that would limit your options as most IGH shifting uses unique cable-pull. Microshift makes drop-bars brake/shifters for Shimano alfine IGHs. I have this setup on my belt-drive bike. You could also have dedicated brake levers and a bar-end friction shifter which will work with any gear system. That would be a super cool setup but it isn't for everyone. A more clean setup would be something like the Gevanalle which has an indexed shifter built into the brake lever. Keep in mind that your IGH would need to be disc brake compatible unless you want to switch the rear to rim-brake.

None of this is impossible and you would have a super cool whip at the end of it but it's not going to be cheap compared to a frame built for belt-drive from the start.

A less committal option is a chain drive with IGH. You would still need the rear triangle modified to 135mm spacing but you wouldn't need a belt split. As long as your frame is steel, this can probably be bent by a frame builder/mechanic for cheaper than adding a belt split. This could use a single-speed chain which would be much more robust than most higher gear chains. It would also be more tolerant of misalignment since belts really need a good belt-line while chains can absorb a couple mm of misalignment.

[–] cvieira@lemmy.ml 2 points 1 day ago

Thanks for the write up! I sort of figured an IGH/belt-drive would involve this sort of complexity. It's an aluminum frame with quick release axles, which complicates things even further. At that rate, it seems to me like a new bike would be the better option.

A local bike shop took a look at the bike, and was surprised to hear about the problem. They said they've never seen anything quite like it, even considering the motor. Their best guess was that the chain-line isn't great, and that could be causing the chain snapping issue in lower gears. The cassette wear can probably be chalked up to it being a $20 cassette.

I think right now, my plan is to try a larger offset on the chain-ring to improve the chain-line. If that doesn't improve things, I'm looking into maybe installing a 5-speed cassette with a thicker chain. This option looks promising, but I'm not 100% sure it will work with my bike: https://www.cycmotor.com/product-page/heavy-duty-drivetrain

[–] jimonthony@lemmy.zip 3 points 1 day ago (1 children)

Shimano makes drivetrains designed to work with motors so I’d probably start looking there for your chainring, cassette, chain and derailleur.

[–] cvieira@lemmy.ml 3 points 1 day ago

I noticed this in my research, but it looks like these drive-trains might be specific to Shimano e-bike motors. I'm more looking for something I can retrofit generically. Do you know of any Shimano e-bike capable cassettes/derailleurs that aren't motor-specific?

[–] yuman@programming.dev 2 points 1 day ago (1 children)

zero experience with the thing, but I'd appreciate some pictures of that setup. thanks.

[–] cvieira@lemmy.ml 1 points 1 day ago* (last edited 1 day ago)

It's nothing terribly exotic. The only real mechanical difference against a typical road bike is that the main chain-ring can spin independently of the pedals on a ratchet mechanism, which allows the little motor in front of the bottom bracket to spin the chain-ring without spinning the pedals. Everything excluding the cranks is just an off-the-shelf drive-train, and you can pedal it normally.