Gearing.

Electrically assisted bikes, trikes, etc.
mattsccm
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Gearing.

Postby mattsccm » 29 Aug 2020, 9:14pm

Just wondering after looking at a selectipn of ebikes in a shop. Why do they all seem to have a single chain ring and a small one at that? My cynical wife reckons it is because the riders are unfit(they must be or they would not ride such a thing) and thus can't go fast any way and will be screwed when the speed limiter comes in.
This last week I have been riding the steepest hills I could find in Yorkshire and having injuries to both legs plus knees needing a rebuild I fitted a MTB double. 42 outer was way too low to press on on the long gentle drops or even on the flat. A 42 seems to be bigger than most fitted.
I am only looking at crank based engines of course.

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Tigerbiten
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Re: Gearing.

Postby Tigerbiten » 30 Aug 2020, 5:05am

Probably a mix of practicality, simplicity and cost.
To keep cost down, you're probably looking at a 1x 9 speed with a max sprocket size of 34 teeth.
You can go bigger max sprocket size and/or more sprockets/chainrings, but that starts adding cost/complexity.
This gives you a max gear range of around 3x.
They're not building them for TdF wannabes, so probably realistic gearing.
This means a first gear of around 30" for hill climbing, which probably gives you a sub-100" top.
This is opposed to the rough 120" top gear on a road bike, that would give you a first gear of around 40" which would make hill climbing hard work even with a motor.
You know wheel size, sprocket size and gearing, from that you can workout chainring size.
30" first gear / 27" wheel x 34t sprocket = 37.7 teeth.
So around a 38 tooth chainring matches the above criteria.
Hence small chainring sizes.

Luck ........ :D

mattsccm
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Re: Gearing.

Postby mattsccm » 30 Aug 2020, 7:29am

Was looking at the higher end stuff as well so 11 speed. Looks like my wife wasn't far off.
Is a double chain set ever fitted to crank based engined bikes?
Not looking to buy, more intrigued. If I was in the market I would want my road bike with some hill climbing oomph added. Low gears wouldn't be needed then.

Jdsk
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Re: Gearing.

Postby Jdsk » 30 Aug 2020, 7:41am

What an interesting question.

Is a bigger range now available at the rear because of the trend to double and single front chainsets?

Does it make easier and cheaper for the sensors?

Jonathan

PH
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Re: Gearing.

Postby PH » 30 Aug 2020, 8:06am

mattsccm wrote:My cynical wife reckons it is because the riders are unfit(they must be or they would not ride such a thing) and thus can't go fast any way and will be screwed when the speed limiter comes in.

She's wrong, people choose to ride assisted bikes for all sorts of reasons.
A 42 seems to be bigger than most fitted. I am only looking at crank based engines of course.

42 x 11 is about what you'll get on the sporty models, at a leisurely 90rpm that equates to around 30mph on 700 x 35 wheels/tyres. Just how fast do you want to go?

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Tigerbiten
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Re: Gearing.

Postby Tigerbiten » 30 Aug 2020, 9:38am

Jdsk wrote:What an interesting question.

Is a bigger range now available at the rear because of the trend to double and single front chainsets?

Jonathan

I think it is a bit chicken and egg.

The latest and greatest "part" was a cassette with one more sprocket .... :)
But adding a sprocket lets you extend the range whilst keeping all the old sprockets
Therefore the latest and greatest "part" is also a cassette with more range ...... :D

The wider the cassette became the harder it was to the setup a triple that won't suffer from chain rub with an indexed shifter.
Hence triples fell out of favour.

Now the latest and greatest "part" is still a cassette with one more sprocket .... :lol:
But the wider the cassette becomes the harder it is to the setup a double that won't suffer from chain rub with an indexed shifter.
So doubles are falling out of favour.
Therefore the latest and greatest "part" has to be a cassette with even more range ...... :roll:

Luck ......... :D

Nigel
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Re: Gearing.

Postby Nigel » 30 Aug 2020, 7:57pm

mattsccm wrote:Just wondering after looking at a selectipn of ebikes in a shop. Why do they all seem to have a single chain ring and a small one at that? My cynical wife reckons it is because the riders are unfit(they must be or they would not ride such a thing) and thus can't go fast any way and will be screwed when the speed limiter comes in.
This last week I have been riding the steepest hills I could find in Yorkshire and having injuries to both legs plus knees needing a rebuild I fitted a MTB double. 42 outer was way too low to press on on the long gentle drops or even on the flat. A 42 seems to be bigger than most fitted.
I am only looking at crank based engines of course.


Some are quite low top speeds; they're 7 speed hub gears, and geared at the lower end of the range. So they "top out" for pedalling fairly slow. An elderly friend of mine has one like it - a "serious" cyclist all his life, but age means his legs don't get up hills as easily any more.
But perhaps that's not what you're wanting to buy.

There are "racing like" electrics with normal road gearing: 50/34 front and 11-28 back, eg. this Cube which is similar to that offered by various brands
https://www.cube.eu/en/2021/e-bikes/roa ... k-edition/

On mountain bikes, there is a general fashion to 1x gearing on non-electric bikes - small single front ring, huge range cassette. That fashion will be dictating the gearing available.

mattsccm
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Re: Gearing.

Postby mattsccm » 31 Aug 2020, 9:01am

Ta. Just wondering rather than buying.
To my mind the modern wide range cassette is horrible. Too many gaps , a big heavy cassette and a vulnerable long mech. But that's me. Should I buy such a bike I would want something that just gives me the extra push on hills when I can't keep up with younger, fitter club mates. Currently a 50\34 CS with 11-28 on the back is about right but a touch gappy. I don't regard 90 rpm as leisurely, never could twiddle and chain gangs don't suit low gears.
Back to my question in another way. Could a larger chain ring be fitted or would this mess up the motors gearing.
Here's another question. Correct definition of engine and motor? :D

Antbrewer
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Re: Gearing.

Postby Antbrewer » 31 Aug 2020, 10:43am

In answer to Mattsccm.

Quote ''Is a double chain set ever fitted to crank based engined bikes? '' unquote.
Yes, I have a Cannondale synapse Neo 1 with a double chain set at front 50/34 and 11 sprockets at rear 11/34. 22 gears in all with a Bosch active line bottom bracket motor.
Excellent piece of engineering and a superb ride. Just over 18 kg.

hjd10
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Location: Originally from Lancashire but now in Lincolnshire

Re: Gearing.

Postby hjd10 » 31 Aug 2020, 9:39pm

mattsccm wrote:Just wondering after looking at a selectipn of ebikes in a shop. Why do they all seem to have a single chain ring and a small one at that? My cynical wife reckons it is because the riders are unfit(they must be or they would not ride such a thing) and thus can't go fast any way and will be screwed when the speed limiter comes in.
This last week I have been riding the steepest hills I could find in Yorkshire and having injuries to both legs plus knees needing a rebuild I fitted a MTB double. 42 outer was way too low to press on on the long gentle drops or even on the flat. A 42 seems to be bigger than most fitted.
I am only looking at crank based engines of course.

Doesn't really matter what the wife thinks, give one a test ride and find out. :D

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531colin
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Re: Gearing.

Postby 531colin » 31 Aug 2020, 9:47pm

mattsccm wrote:Just wondering after looking at a selectipn of ebikes in a shop. Why do they all seem to have a single chain ring and a small one at that? My cynical wife reckons it is because the riders are unfit(they must be or they would not ride such a thing) and thus can't go fast any way and will be screwed when the speed limiter comes in.
This last week I have been riding the steepest hills I could find in Yorkshire and having injuries to both legs plus knees needing a rebuild I fitted a MTB double. 42 outer was way too low to press on on the long gentle drops or even on the flat. A 42 seems to be bigger than most fitted.
I am only looking at crank based engines of course.

Friend of mine rides something that looks a bit like this....https://www.bing.com/images/search?view=detailV2&ccid=ocK%2fqs3e&id=CAB6DAA33A817CA369F87C087580FA84E173DBDF&thid=OIP.ocK_qs3evEnUAfcTj67vPwHaE8&mediaurl=https%3a%2f%2fwww.bikeexchange.com.au%2fdbimages%2fArticleImage%2f79%2f79%2ffullpage_Bosch_eBike_Systems_BikeExchange_moustache_bikes.jpg&exph=667&expw=1000&q=Bosch+eBike+Systems&simid=607994681522719947&ck=137FF0B0416C406DCB4815E044AB70CC&selectedIndex=26&FORM=IRPRST&ajaxhist=0
His top gear is about the same as mine. Conclusion; the drive from the cranks to the chainring must be geared.

hemo
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Re: Gearing.

Postby hemo » 31 Aug 2020, 10:56pm

The mid drives with small front sprocket use internal gear reduction to enable it's use but at the expense of friction/drag with no power. Some still use or are reverting back to a larger front ring with less internal gearing as many have found that they wish to ride without power sometimes, the latter makes it easier to ride unassisted. It is all down to motor gearing and what one wants from the bike.

redcoatuk
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Re: Gearing.

Postby redcoatuk » 3 Sep 2020, 8:20pm

The bike I bought had a 9 cassette with 11-34. Its a Hybrid. That has proved not to be enough up the hills. I have a shimano e6000 steps with 3 power settings. The Mrs has Bosch and has an extra power setting, and she cruises past me on the hills. 34 isn't enough for the Hampshire hills on the minor roads, and certainly wasn't on the Isle of Wight.

I have changed my cassette for a 10 speed, 11-42 and I can get up all the hills now.

So my advice is nothing less than a 36 big cog on the rear :)

mattsccm
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Re: Gearing.

Postby mattsccm » 12 Sep 2020, 10:16pm

Not buying yet. Just wondering as I am one of the grumpy old sort who fails to see the problem with a nice triple and a tight cassette. As I can still just about go below 26 for a club 10 I think I can wait a bit before I need the push. Now her ladyship on the other hand..........

mattsccm
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Re: Gearing.

Postby mattsccm » 12 Sep 2020, 10:19pm

Just read the post above mine. Amazed by the lack of oomph, I had assumed that an ebike would, in effect, take several decades of the legs and would allow a nice straight through, corn cob cassette. As you see I know nowt.