Motor: Crank Drive or Front Hub (because of Nexus preference)?

[williec79]

Hello,

My wife and I are in the throes of buying a replacement electric bike to replace her now defunct Veloscoot. I should say that as we live in France our choice is limited to bikes sold here, but the advice I seek is not with regards to the brand names, but specifically as to which motor type is better for our needs and environment. Also following an accident a few years ago, my wife has pretty week leg muscles, and thus we need a bike which has the “easy start” option up to 6km/h.

Our use is purely leisure with maximum round trip being around 60km. Our locality is very hilly with hills ranging from pretty short & steep to those not so steep but pretty long.

We both are very familiar with bikes having the motor in the front hub and with the Nexus system.

As I have heard good reviews of the motor in the crank position, we have had several test rides with bikes having the Bosch Active Line and one test with a Shimano Steps system. With the exception of one test ride, all the others have been on pretty flat roads so all feedback I was getting was positive.

The other day, we actually bought a bike with the Bosch Active Line and it was advertised as having the “easy start” option. As the test ride was on a main road in a large city, my wife elected not to take the test ride, and to my shame I forgot to use the “easy start” button.

When we got home, the following problems were immediately obvious:

1. The “easy start” option simply did not work.

2. The bike could not easily climb the hills surrounding our house.

After a more detailed ride the next day, the problem on the hills could be identified. If, for example, one approached a hill in 4th gear, and when one changed down one or more gears, although the twist-grip indicator on the handlebar was showing the new gear having been selected, in fact the bike was still operating in the original gear (4th in this example). After a bit of experimenting, it became evident that if one stopped pedalling, the new gears was successfully selected.

I called the shop and to my amazement they said this was normal when a centrally mounted motor was used in conjunction with the Nexus system.

I have started the procedure to get a refund, but can any of your contributors let me know if what the shop claimed is correct?

On the “easy start” system problem, the shop is saying it should have been advertised as “walk assist” only.

Sorry to have been so long-winded.

 

[Artstu]

When we got home, the following problems were immediately obvious:



After a more detailed ride the next day, the problem on the hills could be identified. If, for example, one approached a hill in 4th gear, and when one changed down one or more gears, although the twist-grip indicator on the handlebar was showing the new gear having been selected, in fact the bike was still operating in the original gear (4th in this example). After a bit of experimenting, it became evident that if one stopped pedalling, the new gears was successfully selected.

I called the shop and to my amazement they said this was normal when a centrally mounted motor was used in conjunction with the Nexus system.

I have started the procedure to get a refund, but can any of your contributors let me know if what the shop claimed is correct?

On the “easy start” system problem, the shop is saying it should have been advertised as “walk assist” only.

Sorry to have been so long-winded.

I have a Bosch motor with a Nexus 8 and yes the hub won't change gear under load, a very brief pause in pedalling is required when changing gear. It's second nature for me now and isn't an issue even on 20% gradient hills.

I'd suggest trying to hone the knack before dismissing the bike.

 

[Rosie]

Have just changed to Nexus hub and after a few false starts find it's really good. Just ease off the pedals, change, and the torque will speed you up the hill. Really handy to change down whilst stationary when you stop in a high gear.

R

 

[williec79]

Many thanks to Artsu & Rosie for their replies.

One follow-up question please: is it likely that all “central motor” positions will have the same characteristics. For example, Shimano Steps & TransyX, plus others whose names escape me.

Regards,

Williec79

 

[IR772]

All crank motors need the gears to perform.

The Yamaha system is instant in help where the Bosch needs a couple of turns to start.

But yes they are all similar in operation.

 

[Artstu]

Many thanks to Artsu & Rosie for their replies.

One follow-up question please: is it likely that all “central motor” positions will have the same characteristics. For example, Shimano Steps & TransyX, plus others whose names escape me.

Regards,

Williec79

I'm lead to believe the steps system isn't as powerful as a Bosch system. I also understand that there are gear-change sensing systems available on both systems, linked to the Nexus hub gears, but I'm dubious about how well they work in reality.

I have the classic Bosch and the walk assist is next to useless also. however I really like the way it feels in riding bar perhaps in Eco mode which is just slightly too low powered.

 

[Danidl]

I have the Motus which uses the Bosch active motor and the derailleur gears rather than the hub type. The derailleur gears expect the chain to be moving when changing cogs. The gear change is very smooth , presumably the motor senses that there is no load and reduces power during the transition , certain ly there is no clunking on changing. There is also no electrical connection between the shifting paddles triggers and the motor.
I understand that all the internal hub gears , back as far as the original Strumerly. Archer 3 speed need the chain to be stopped before the gears can disengage. If you look at an animation of a hub gear unit, it is easy to imagine why this might be so.

There are swings and roundabouts here. The hub units are better for changing a gear when stopped and derailleur gears better when the bike is moving.

 

[Artstu]

I understand that all the internal hub gears , back as far as the original Strumerly. Archer 3 speed need the chain to be stopped before the gears can disengage.

That isn't the case with a Nexus, on a normal bike they change up and down under load, perhaps sometimes a very slight easing of the pressure may be desirable, but they certainly don't need the chain to be stationary.

 

[RobF]

All crank motors need the gears to perform.

The Yamaha system is instant in help where the Bosch needs a couple of turns to start.

But yes they are all similar in operation.

The Bosch system is instant, you can feel the assist as soon as you put pressure on the pedals.

Both the Yamaha and Bosch systems operate nicely, although the Bosch feels a bit smoother overall.

 

[Danidl]

That isn't the case with a Nexus, on a normal bike they change up and down under load, perhaps sometimes a very slight easing of the pressure may be desirable, but they certainly don't need the chain to be stationary.

I might have expressed it better. That the chain is stationary is not an absolute requirement, however the hub gear should not be under pressure otherwise the internal gears either will not disengage or will suffer greater wear when engaging. This is similar to trying to change the gears in a car without the benefit of a clutch. If the chain is slower than the freewheel then there is no pressure.

On a non electric bike the pressure exerted by the rider will be typically 50%" that of the electric bike so disengaging will be proportional ly easier. On the Bosch systems on maximum assistance the total pressure will be 375% that of an unassisted user.
The Nexus user manual advise slowing down the peddling when changing.

 

[Crockers]

When I was a kid I was told to back pedal when changing down on my Sturmey Archer 3 speed. I'm assuming it's like driving a manual car.. foot off gas depresss clutch etc

 

[D C]

When I was a kid I was told to back pedal when changing down on my Sturmey Archer 3 speed. I'm assuming it's like driving a manual car.. foot off gas depresss clutch etc

Me too, couldn't wait to get "proper" derailleur gears.
Any one remember double de-clutching?

 

[anotherkiwi]

Me too, couldn't wait to get "proper" derailleur gears.
Any one remember double de-clutching?

My best friend in NZ still drives his 1967 Holden with 3 speed racing box! I learnt to double de-clutch in that.

I drove my 1955 VW Beetle for a couple of weeks without the clutch. After I found where the clutch wire was "broken" I never used it when the car was moving. That was a gear box with great sychro!

 

[Rob Hardy]

Me too, couldn't wait to get "proper" derailleur gears.
Any one remember double de-clutching?

I do remember double de clutch, in the old pre synchro days. Driver today have it easy.....(groan moan mumble mumble.)

 

[Trevormonty]

Shimano Steps with Shimano Di2 Alfine hub might be better option. Motor controller reduces power during changes plus alfine is better at changing under load than nexus. Other plus is drive system automatically selects low gear when stop for easy starts. There is also option of automatic gear changes but reviews are mixed on this.

Bosch may support Di2 on newer models.

If ultra low gearing is required for hills, get chain driven hub. Any shop can lower overall gearing by changing rear or front sprocket. In theory it can be done with gates belt drive but maybe more expensive job.

 

[anotherkiwi]

That was once almost true. The Alfine 11 speed has never been recommended with a crank drive.

There is now a "premium" version of the nexus 8 inter which uses much of the internals of the Alfine 8. And to make things even more confusing for the buyer there is even a new disk brake version which makes the hub an Alfine in nexus clothes...

And yes there is a Di2 version of the nexus 8 too.

Most of the pedelecs I have seen use the cheap version of the nexus 8 however, leaves more profit margin for the manufacturer.

 

[RobF]

A problem, as Kwi says, is there are different types of Shimano hub gears.

I have an Alfine 11 on my Rose/Bosch bike, so it's tempting to say I know about Shimano hub gears, but I don't because the others all perform a bit differently.

The Alfine 11 changes best with the pedals turning under moderate load.

As regards start assist on Bosch bikes, I recall the original Classic Speed motor had this - it was outlined in the instruction manual.

But I've not heard of it since on a Bosch bike.

To me, start assist is not required because pulling away in turbo is quite lively - you get an all but instant prod forward which for most users should be enough to get the job done.

Gearing can be tinkered with on hub gears by changing either or both of the cogs.

Shimano publish maximum/minimum tooth combinations to avoid over-torquing the hub.

The lowest on the Alfine 11 is not especially low - lots of complaints about that from touring push bike owners who like a crawler gear for loaded climbing.

If really low gears are required, a derailer bike would be a better choice.

 

[Artstu]

Shimano Steps with Shimano Di2 Alfine hub might be better option. Motor controller reduces power during changes plus alfine is better at changing under load than nexus. Other plus is drive system automatically selects low gear when stop for easy starts. There is also option of automatic gear changes but reviews are mixed on this.

Bosch may support Di2 on newer models.

If ultra low gearing is required for hills, get chain driven hub. Any shop can lower overall gearing by changing rear or front sprocket. In theory it can be done with gates belt drive but maybe more expensive job.

Nexus for rim brakes, Alfine for disc brakes, the same internals.
You need a frame that separates to get a belt on.

 

[williec79]

Thanks everyone for their contributions, especially Artsu.

An update on the story is that we took the bike back to the shop and the somewhat unhelpful salesman told us that we would be dealing with someone else who was the under manager. His attitude was very different and he listened to our “complaints” without interruption.

He said he could not do anything on the lack of an “easy start to 6km/h” and he conceded that the bike should not have been so advertised. He took the bike into the service bay and made some adjustments and asked that we try the bike again, which we did outside the shop. I have to say the Bosch/Nexus “problem” of the hub not engaging a lower gear immediately when climbing a hill, had vastly improved, but the hesitation was still noticeable.

However, the bike also, was still less successful in climbing the test hill than my own ebike with a front-hub motor.

The under-manager fairly readily accepted that we had the right to cancel the purchase & return the bike as the lack of “easy start to 6km/h” had been an essential requirement to our purchase. This being due, as mentioned previously, to my wife’s leg muscles being severely weakened following an accident.

Finally, one point has just come to mind, and it may or may not be relevant to the problem we experienced with the Nexus not immediately changing gear under load. The bike in question had the “retro-pedalage” or coaster brake option. Could a mal-adjustment of this be a contributory factor in the problem?

 

[flecc]

Any one remember double de-clutching?

Yes, double-declutched for many years in both cars and trucks.

Similar to Anotherkiwi I also had a much more recent spell of clutchless driving. Two weeks before a new car was about to arrive the hydraulic clutch on the old Fiat failed with a big leak, so I did all my trips clutchless for that time. Being in town that meant starting in bottom gear (or reverse gear when exiting my garage) and of course switching off and restarting in gear when traffic lights stopped me.
.