Looking for a fast road-legal pedelec / bike with pedelec upgrade

[flecc]

From what I've read the Rohloff has a 527% gear spread, an 11 speed Shimano 408% and an 8 speed only 307%.

For amusement Feanor, the ultimate range can be had by using the excellent SRAM DualDrive. This combines an 8, 9 or 10 sprocket cassette mounted on a speed hub, all operated from one clever control. The idea is that the 3 speed hub equates to a triple chainring where that isn't desirable for some reason, but the DualDrive can still be used with a triple chainring if desired. The result using the DualDrive 30 with a triple chainring and it's second control can achieve 90 gears, easily covering 1800% or more range!

SRAM DualDrive

 

[Cakey]

I have rohloffs on 2 of my ebikes. I would not buy a bike with a rear mech out of choice again.
Hence why I like the Bosch haibike with Rohloff

 

[Feanor]

For amusement Feanor, the ultimate range can be had by using the excellent SRAM DualDrive. This combines an 8, 9 or 10 sprocket cassette mounted on a speed hub, all operated from one clever control. The idea is that the 3 speed hub equates to a triple chainring where that isn't desirable for some reason, but the DualDrive can still be used with a triple chainring if desired. The result using the DualDrive 30 with a triple chainring and it's second control can achieve 90 gears, easily covering 1800% or more range!

SRAM DualDrive

Haha that's mental!

I have rohloffs on 2 of my ebikes. I would not buy a bike with a rear mech out of choice again.
Hence why I like the Bosch haibike with Rohloff

Interesting - what's your view on how well-utilised the range of gears on a Rohloff are on an ebike? In your experience do you think it gives an advantage over the Shimano hubs?

 

[wissy]

My KTM Macina arriving Thursday ... Yee ha! .... Has dual sram things... BUT I didn't understand a word of what you meant up there!?

More gears...? Or more gears if I do change something??

 

[Feanor]

My KTM Macina arriving Thursday ... Yee ha! .... Has dual sram things... BUT I didn't understand a word of what you meant up there!?

More gears...? Or more gears if I do change something??

He meant if you change something .

Most bikes have gear cogs at the front where the pedals are and gear cogs on the back wheel. This means you have two separate controls - one for the front gears and one for the rear gears. This can be confusing and fiddly. The total number of gears is calculated by multiplying the number of gear cogs at the front with the number of gear cogs at the back (so let's say 10 gears on the rear cogs and 3 gears on the front cogs = 30 gears).

On your bike, the 3 cogs at the front are replaced by a 3-speed rear hub gearbox which provides the same multiplier function. But because of the mechanics of how the system works you don't need a separate control - everything can be done from a single control.

What flecc was suggesting is putting 3 cogs where the pedals are anyway along with a separate control. This would mean you would have 10 gears x 3 gears x 3 gears = 90 gears.

All the percentages just relate to how much harder you have to pedal in the top gear compared to the bottom gear. So if you had a 20% gap between each gear, gear 1 would be 0%, gear 2 would be 20% harder, gear 10 would be 200% harder (ie three times as hard) and gear 30 would be 600% harder. With 90 gears, gear 90 would be 1800% harder.

In practice though I'm not convinced how well this would work without using custom cog sizes as you'd surely get a lot of duplication, but I haven't given it any thought so might be wrong. Calculating gear ratios is complicated and although my job is a multi-discipline technician/engineer maths was always my weak point! (Fortunately I have found that in my job common sense, logic and people skills are far more important - not that I'd claim to have much more sense than is common! ).

Anyway, I seem to be helping "derail" my own thread here!

 

[flecc]

Percentages are not too difficult to work out for sprocket combinations, it's simply arithmetical via the tooth combinations. If a rear cluster's sprockets range from 11 teeth to 33 teeth, that's 300%, 33 divided by 11 and times 100. So a cluster of 9 to 24 teeth is 24/9 x 100 = 267%.

The three speed hub on the SRAM DualDrive has a 200% range to be taken into account also by multiplying 2 x 3 to give 600% range in the first example.
.

 

[RobF]

By common consent, the Rohloff is the finest hub there is, so it follows that you won't go far wrong with one.

And you can always tinker with the sizes of either of the sprockets.

All ebikes have a knack to riding which you soon learn, but to generalise cadence speeds are slower than a normal bike.

I believe most riders find they use fewer gears, which is why I think you don't need the 14 speeds of a Rohloff.

For example, I'm just back from a 20-mile round trip on my Brompton Nano in which I only used gears four and five (out of six) and didn't change very often.

Top speed on a legal bike will depend on how easy the bike is to pedal above about 15mph when the motor stops assisting.

My experience is this varies a lot, my Brompton Nano just doesn't want to go much faster than 15mph, no matter how hard I try.

Forum member Alex on here has a C11 Alfine Kalkhoff which will go faster.

I tried a couple of legal Kalkhoffs and found the same, I recall getting 20mph or so out of one without too much effort.

That's unlikely to be Kalkhoff-specific, I imagine any reasonably light Bosch hybrid on narrowish 700c tyres would do the same.

 

[wissy]

I'm getting worried.. i understood that....

Many gears not needed usually or chain goes 'chrchrcgh' ?

 

[Electrifying Cycles]

Wissy no need to worry. Advantage of having more gears is you can take advantage of this fact on flat or downhills. Most electric bikes have less gears as you need less gears due to using motor to help go up hills. However I find they do come in handy but just not essential like a traditional push bikes. I like to ride them fast so prefer more gears or higher percentage ratios. Hope this helps. Looking forward to your thoughts when you take your first few rides.

 

[Feanor]

I've found a couple of threads about the Sunstar iBike on a German forum (my German is reasonably fluent and my partner is German) where I came across this image. It's exactly what I have in mind in combination with a good road/commuter bike (Santos?) instead of a single speeder:



Since people at the German forum seem to have used the iBike I'm going to ask if there are any downsides, such as whether the motor will destabilise a high-end well-balanced bike at all, but the more I think about it the more the upsides to this make sense to me:

1. I'm not sure I would really get the most out of a pedelec at the moment as I don't need/want cycle far enough for it to be worthwhile. So I can get the bike sooner and add the kit later as my needs change.
2. I can get exactly the bike I want, fitted to me.
3. The kit can be replaced when it becomes obsolete and I'll still have a good bike that'll last.
4. It'd be lightweight and still have a good top speed.
5. With a lightweight motor & battery I think the Rohloff would not be wasted as I'd still be able to cycle without the pedal assist perfectly well if the battery ran out or I wanted to conserve juice. My understanding is that most ebikes are horrible to ride if the battery is flat but with this setup that shouldn't be a problem.

Against that, the possible downside of upsetting the bike's balance slightly doesn't seem very significant.

I'm still grateful for any input on this though as I'll be mulling this over for a few months to come.

 

[jackhandy]

Sounds like you may have found your bike

The motor/gearbox & battery are in what's generally considered to be the best position for balance & you have the option of a rack-mounted extra battery for when you want endurance.

 

[flecc]

The Sunstar SO3 motor unit is quite light and shouldn't destabilise the bike in any way. It's one of the lower powered motors around, but it's light assistance suits a fit cyclist on a good road bike.

The unit is quite sophisticated in the Panasonic and Bosch crank-drive manner, unusual for a crank drive kit motor since most of this type have quite simple and often crude software.

If you are happy with the fairly light assistance it's a good choice.

 

[Feanor]

Thanks both. I hadn't realised it was lower powered than other motors but as you say power isn't very important to me. I'm fairly fit and relatively young (28) so am mainly looking at being able to get to work a bit less sweaty and a bit less exhausted while making a good time, rather than taking most of the effort out.

The S03 seems to be very popular in Germany but one downside has come up. I read in another thread on this forum that the motor carries on for a couple of seconds after you stop pedalling, so I asked about this because it sounds dangerous. The response was that it's not so dangerous but could be a bit annoying as it's best not to change gears with the Rohloff when the pedals are under torque, so could make gear changes difficult. I've asked if anyone knows why this is - I haven't heard the same thing said of the Bosch motor?
I can't help but wonder whether maybe it'll be fixed if they release an S04 - as said I may not get a pedelec upgrade this year anyway so it'd be nice if such an upgrade came out.

Also, does anyone know if the S03 makes it harder to pedal once the battery runs flat? Would you be fighting against the motor coils and electromagnets?

 

[flecc]

Also, does anyone know if the S03 makes it harder to pedal once the battery runs flat? Would you be fighting against the motor coils and electromagnets?

There's aren't large differences between the Sunstar SO1, SO2, and SO3 kits, just some power increases (the SO1 was a 180 watt rating with a tiny battery) and battery changes as far as I can see, so I doubt the changes in the SO4 will be radical.

Richard Peace, a respected cyclist and cycling book author has test-reported the Sunstar kit twice on his recumbent, once for A to B magazine when he first fitted it and once for VeloVision after he'd gained more experience of riding with it. In the A to B test he mentions the value of the off switch that he used freely to conserve that earlier unit's tiny battery, but made no mention of any drag on those occasions of pedalling only, so we can probably safely assume that like most good crank units, there's none to speak of.

Also in that A to B test he mentioned that at first the pedal power responses were rough, but he was advised to try altering the DIP switch settings. These units have a row of DIP switches in the handlebar unit that can be set in various ways, and he found that having them all off cleared the problem completely. Obviously these switches enable one to tune for each bike setup.

The later VeloVision test review is available online for you to read on this link
.

 

[Feanor]

Thanks. I hadn't realised you have to fit their proprietary bottom bracket. I assume this makes compatability with a belt drive difficult or impossible?

 

[flecc]

I don't know the answer to that, but it may well rule one out. It's a problem with many crank drives that the choice of chainwheel is very restricted or non-existent.

 

[Electrifying Cycles]

Worth noting that Grace bikes have a crank drive with a belt drive while AVE have models which are belt drive ready. So it is possible on some crank drive systems, not sure if it is with the one mentioned above.