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E-bike: gateway drug or 'the answer'?

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  1. Arellcat
    Moderator

    It oughtn't to be so surprising that e-bikes are heavier on transmissions. It would be interesting to know the average (or RMS, maybe) power output at the sprocket, compared with a purely human powered bike. And it would be interesting to know if heavier chains are ever specified.

    Playing fast and loose with some numbers, supposing an e-bike rider+motor allows for a time-averaged power output of 150W, that's somewhere between 175 and 270 times less than what my not-especially-powerful 55bhp motorbike will do, depending whether I ride it the way I usually do (fairly slow and puttery) or if I caned it all the time (red mist, evening jaunts and motorway dashes).

    But the chain on my motorbike is massive: it weighs about 2kg! A Sram single speed chain is only 330g; a typical 9-speed chain about 300g. So a chain that is objectively only six times more massive can handle 175 times more power. It lasts for 10,000, maybe 15,000 miles, yet 'only' costs about seven times more than a 9-speed chain.

    A piddly Honda CBF125 puts out over 50 e-bikepower, yet takes a DID 428 chain that costs less than £20.

    I realise that we have a lot of derailleury e-bikes going around, but for the hubgeared ones, are makers simply using the wrong equipment?

    Posted 2 years ago #

  2. chdot
    Admin

    “are makers simply using the wrong equipment?“

    Quite probably, though (maybe) another byproduct of the industry/marketing ‘need’ for faster/lighter.

    More gears means more compromises - particularly in product/wear life.

    Though presumably the serious E-bike manufacturers are aware of this and considering options(?)

    Perhaps go back to the previous standard of 1/8”??

    3 speed chains were sometimes used for decades - often with completely hooked teeth on chainwheel and sprockets...

    Posted 2 years ago #

  3. steveo
    Member

    Alternatively a rear wheel motor takes a lot of the strain off the drive train, in ideal circumstances only needed as a sensor to say the rider is pedaling and bring in the power.

    The motor on mine is small and struggles with my fat self on hills so needs some input and being a single speed this sometimes translates into a lot of torque. I'm sure the belt drive is upto it but the plastic chainwheel doesn't fill me with confidence on the odd occasion I have to put some extra power through it.

    Posted 2 years ago #

  4. LaidBack
    Member

    @steveo - what make is that? (Sorry will be downthread). Bike Works reckons that mulitigears are wasted and of course e-bikes have users that don't work with gearing anyway as attracting 'new cyclists'.

    But of course cycling is a fashion business and easier selling a 10 speed bike (eg Dave's Nihola) versus the classic Nihola cargo trike with a mere 7 speeds on a hub motor.
    The 10 speed with Shimano mid-drive 'feels' better to use as do the Bosch/Yamaha/Bafang crank drive models. Power assist cuts in as soon as pedal moves so gives a 'servo-assisted' feel. Hub motors though do cause less chain wear of course.

    One 'odd' thing is that Shimano's forward planning had made sure gearing options were intergral to the Di2 system that runs the motor. Their latest e-bikes offer a 5 speed hub as more robust than Alfine or Nexus 8 speed. 5 gears are enough really. Their e-shift Di2 screen displays the gear but hub gear works nicely manually too and old style display faster to read.

    Bosch of course sell loads of motors but rely on 'bike companies' to provide gearing.

    You might have expected Sturmey Archer to have gone into this e-bike hub market but no sign of that.

    (Sold a few models with Gates belt drive but had a belt sprocket with broken splines)

    Posted 2 years ago #

  5. steveo
    Member

    @Laidback its a gtech. Basically a cheap bike with a fancy drive train.

    Posted 2 years ago #

  6. LaidBack
    Member

    @Steveo - that's what I thought.
    J at Bike Works thinks G-Tech is right in it's less 'gear-centric' approach.
    Cost wise it's good value and does the job I'm sure. E-bikes generally wear brakes more as heavier but consumables are a fact whatever the price level a bike is bought at.

    One recurring 'theme' when selling an e-bike though is "can I pedal it with no power/battery left?". The answer is yes but a bigger spread of gears will help.

    Posted 2 years ago #

  7. steveo
    Member

    Yeah, the lack of gears and belt drive for me made it a great choice for commuting, only other thing I would add is disk brakes. Course I got it a week before lockdown so never once used for a commute!

    It could do with a bit more grunt there are some hills where the speed drops to ~10mph and you can really feel the torque from the motor. On the flat I get to about 14mph and before the motor cuts out but the gearing is such that its easy enough to keep pedaling to about 16mph-17mph before your just wasting energy. Its also easy enough to ride powerless but the gearing is a bit high for starting off.

    Posted 2 years ago #

  8. Dave
    Member

    I've never ridden a hub motor and would be interested to compare.

    We have both Bosch and Shimano mid drive. The Bosch seems perhaps more powerful (although that could simply be a new longtail VS an older e-bike towing a trailer) but I prefer the feel of the Shimano STEPs motor to Bosch.

    The Bosch assist feels over-sensitive, it changes the power too rapidly based on what my feet are doing, so if I'm not just plowing on at full speed it makes everything more jerky. The Shimano assist is probably dumber, but it is noticeably smoother when you're negotiating a gate / path entrance / etc.

    Posted 2 years ago #

  9. steveo
    Member

    The mid drive full suspension bike I hired at Cromrie had more in common with a MX bike but it had many more torques. But it was such a different experience to a rigid commuter.

    I can't remember if it was shimano or bosch but was much nicer but then it was a £5k bike and the drive system was basically replacing a chair lift!

    Posted 2 years ago #

  10. ejstubbs
    Member

    @Dave: The Bosch assist feels over-sensitive, it changes the power too rapidly based on what my feet are doing

    I've never ridden a STEPs-powered e-bike to compare, but I'd agree that the Bosch system can feel a bit jerky. As fitted to my eMTB (2018 Performance Line CX) I find it wholly unsuitable for technical climbs on any setting higher than Eco, which basically just compensates for the additional weight of the motor+battery. Getting a hefty 'kick' of assitance just as you try to nadger your way round the apex of a tight uphill hairpin is not helpful.

    Tour mode is more or less OK, and can in fact (though perhaps counter-intuitively) be useful on downhills such as Spooky Wood, giving a bit of extra oomph out of slow corners (or to put it another way: corners that you* chicken out of taking at full downhill speed at the last minute!) It can be a bit jerky away from rest, though.

    Turbo mode is great for blatting up boring fire roads but not much else. I find I can usually change up two gears as soon as I engage Turbo, so it's fast but it's not very controllable - it basically seems to work like an on/off switch: if you're exerting any kind of torque on the pedals at all then it provides full assistance, there doesn't seem to be much of a graduation in the delivery.

    eMTB mode I find puzzling: it's supposed to adjust the assistance level automatically between Tour (120%) and Turbo (300%) but somehow always seem to be giving me either too much or not enough. I've basically given up using it after one too many almost-being-flipped-over-backwards experiences on steep rock steps. (Some owners of pre-2018 Bosch systems were none too happy with the "upgrade" from Sport to eMTB that was applied when they got their bike serviced.)

    I know that Bosch claim that their more recent systems have even cleverer software so maybe newer ones are more forgiving. It's just a shame that, a bit like mobile phones, there seems to be no way to get the latest firmware installed on systems that are more than a year or two old. Definitely a step backwards in eco-friendliness IMO.

    * i.e.me.

    Posted 2 years ago #

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