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I just bought this Aventon Level ebike https://electricbikereport.com/aventon-level-review/ I was wanting to upgrade the derailleur, but I'm not sure which one to get. I don't want the entry level/lowest level derailleur, but am having a hard time finding a 8 speed Shimano one.

This is the current one it comes with: Gearing: Shimano Acera 8 Speed/Shimano Acera Cassette, 12-32T, 8 Speed

Thank you this bike stuff is new to me I have another ebike, but didnt need to upgrade since the parts were higher quality.

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    I'm not sure why you're replacing a brand new derailleur - it can't be worn out already. You're not increasing the number of gears, so the benefits seem unclear. Could you use edit to expand on your goals here? Acera is perfectly serviceable, and if its not working then tune it up. New bikes often need a tweak after a month of use to adjust for cable tension and so on.
    – Criggie
    Jun 6 at 10:38
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    Acera is probably as good as it gets in 8 speed
    – Andy P
    Jun 6 at 12:43

3 Answers 3

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If you want a real upgrade, my recommendation would be to upgrade not only the derailleur, but also the cassette and shifter to have a more modern system (transmission for single chainring systems, with clutch derailleur).

The reason is quite simple: 8-speed systems are now only entry-level, and are often used with triple chainrings. Cassettes have then very small range, and it's not by upgrading only the derailleur that you'll have a significantly better experience: I don't know about 8-speed Deore XT for example, but 9-speed Deore XT could only handle 11-34 cassettes, which is not significantly different to what you have (260% range vs 300%) - it will feel better for sure, but won't be functionnally much better.

By contrast, if you switch to a modern 1x system, you'll have more range and thanks to the clutch derailleur, you'll have less chain drops over rough terrain. That will significantly improve your bike.

At the time of writing of this answer, the "starting" configurations for modern systems are:

  • Microshift Advent: 9-speed, 11/42 or 11/46 cassettes (380%/420%).
  • Microshift Advent-X: 10-speed, 11/48 cassettes
  • Shimano Deore M5120: 10-speed, 11/46 cassettes
  • Shimano Deore M5100: 11-speed, 11/51 cassettes
  • SRAM NX Eagle: 12-speed, 11/50 cassettes

In 12-speeds, things are a bit more complicated: because cassettes very often require another freehub body (to be able to use smaller sprockets than 11), which often require to replace the hub and then the wheel.

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You'll need any 8 speed derailleur from Shimano or another manufacturer.

As a rule of thumb, the differences between road and MTB, and differnet maker's designs only start to become an issue at 10 speed, and get progressively worse as the number of gears increases.

You could get any rear mech from the Shimano budget Tourney, or a Claris road 8 speed. On the MTB side:

  • Tourney (this is the bottom entry, and is classed as MTB but you find it on everything cheap)
  • Altus
  • Acera (your current spec - not bottom but comfortably in the "perfectly acceptable" middle of the range)
  • Alivio
  • Deore (getting expensive)
  • SLX
  • Deore XT
  • XTR (top dollar, and uncommon)

Shimano Zee and Saint are MTB downhill-specific and probably too new to come in 8 speed.

SRAM 8 speed seems to be uncommon, so you might also consider Microshift and other smaller specialists.

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  • This is not true. Sram and Shimano have very different pull ratios. Jun 6 at 21:24
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    @manderDon'treinstateMonica remember we're talking about older designs with 9 gears, specifically. I have 9 speed shimano mech paired wiht a 9 speed sram shifter, for example. Couldn't do that with 10 speed and more.
    – Criggie
    Jun 6 at 21:26
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Here you replace it with the best nominally 9-speed Shimano mountain derailleur you can get. The XT-level RD-M772 is the usual culprit among ones that are available new. There's also a 9-speed Deore with Shadow that is good. (If you found a higher quality vintage 8-speed RD that would also be an improvement, but most of them are scrap metal by now.)

A lot of ebikes come with rear derailleurs that are very ambitiously low-end for their price point. It's insanity. I think plopping in a new RD and calling it good makes a lot of sense.

You do have to think to some degree about the compatibility in terms of whether the new RD can handle the range and the large cog size. Basically all of the pertinent mountain RDs have no trouble here. Most of the road ones are not specced to be able to clear the 32t, otherwise you could look at those too.

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  • I suspect the derailleur is an area of cost saving on ebikes, because this one has a rear-hub motor and won't stress the transmission components at all.
    – Criggie
    Jun 6 at 19:54

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