Why has the Nexus 8 speed hub gear not caught on?

[iRider]

Hi Guys,

As I look around for a good all-round hybrid eBike I came across the Raleigh Motus Grand Tour with a Nexus 8 speed hub gear. Looking further I haven't seen any other eBikes with Hub Gears, instead they tend to be 9 speed Shimano Deore gears or similar.

Why did the Nexus 8 speed hub gear not catch on?

 

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EBOXX E14 • Nicolai Bicycles

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[Artstu]

I think you've misunderstood. When you're go up a steep hill and you stop pedalling to change gear, you stop. You don't have to do that on a Bosch, shimano, Brose or Yamaha with derailleur gears.

James and Flecc have already answered, the briefest pause is all that is required on a good crank drive system, I bet the gear changes are quicker than on a derailleur system, and remember you ease off on those to change gear, well if you have any mechanical sympathy you do.

Oh and having a Nexus 8 certainly doesn't slow me down on the hills as this example shows https://www.strava.com/segments/9919845?filter=overall

 

[Woosh]

You can't pause pedalling when you're going up a steep hill, which is when the load is highest, and you can spout your theories as much as you like about how you can select bottom gear before you start the hill, but we all know that that just isn't practical, and even if it were, it's just not convenient. Woosh, if you believe in your idea, make a bike with crank motor and hub gears and sell them in their thousands, but I guess you don't and won't make one because you know it would be a crappy bike and nobody would buy it. Maybe you're only trying to sell this false narrative to put your competitors out of business.

I fitted gear shift sensors to my crank drive bikes for two years now. Before that, some get it immediately after a minute on the bike, some take longer but nobody reported a problem with changing gears. People get used to shifting gears on a CD bike pretty quickly. However, the gear sensor costs me $10, fairly inexpensive to fit. Same with hydraulic brakes, the cost differential is now only $35, I fit them to most of my bikes.

 

[georgehenry]

"robust electronic 14-speed hub gear Rohloff E-14 with Gates belt drive, an enormous gear range of up to 520% performance and extremely low maintenance requirements"

So they say, at a price of course!

 

[culy30]

Wow, some differing opinions here. Though I'd throw mine in.

Firstly the Nexus isn't totally maintenance free. It runs as a sealed unit and is greased, unlike the £1,000 Rohloff which runs in an oil bath which can be drained and refilled in situ. The Nexus will need to be re-greased every 2yrs or 5,000km according to Shimano. That might put some off as I'm sure lots of e-bikers do more than 5,00km a year. There are various versions of the Shimano Hub gear, the 8 Speed Nexus being just one. Shimano have recently launched a 5 speed hub gear aimed at the E-Bike market. The internals are more heavy duty according to the Shimano propaganda. But is 5 gears enough? They will be more widely spaced, which I personally would not like. I run a 10 speed derailleur setup on my converted e-bike and occasionally I could do with a couple more. But my wife might prefer fewer gears, she isn't.................er.......... intuitive, always changing gear too late and sometimes the wrong way, so she might get on better with 5 than her current 9. It's curious, when she drove a manual car, she didn't try to go up steep hills in top gear. Perhaps she's driven an automatic for too long.

With most crank motors having sensors to reduce power when changing gear, I really don't think the load during changes is an issue. Another feature of the top end hub gears is the electronic gear change option. Many would find this a benefit.

I have ridden the 8 Speed Nexus on an ebike. It was great, I loved it. It was hilly. (Bavarian Alps) Its cleaner too, most quality ebikes have chain guards and there are fewer external movings parts exposed to road dirt. Most commuter/city/touring ebikers would find this an attractive feature.

I see Raleigh offer an 8 speed Nexus ebike at a premium of £100, which doesn't sound too bad to me.

As for the efficiency argument, that intrigues me. A derailleur in perfect tune and clean is pretty efficient when the chain is in a fairly straight line. ie the middle three or four gears. I'll now see if I can find some tests comparing IHG with derailleur so I can help my wife make an informed choice when I decide to buy her a new bike!

 

[culy30]

Well I didn't find a definitive answer to my efficiency question of derailleur vs Internal Hub Gear or is it Internal Gear Hub? Most opinions range from the Hub Gear being 3%-8% less efficient compared with a well tuned, clean derailleur. For an ebike, I don't see this being a huge issue, especially when we all know that the derailleur loses efficiency when it gets dirty and when using gears at the extreme ends of the cassette.

Having given this some more thought, I'm sold on the Internal gear for an ebike that does most of its mileage on tarmac, gravel or hard trails. There are pros and cons, one of which is fixing a rear puncture, so when we get around to getting one, I'll probably go for a tubeless rear tyre with good puncture protection. Converting a non tubeless rim is easy and successful provided you use a tubeless ready tyre, I've done it a few times.

My wife is testing the Raleigh Motus Grand Tour step through, with Nexus hub and 26" wheels at the weekend. If she likes it I'll come back with a report. (They also offer a 700c version in the same 46cm frame size, but the 26" should be easier to handle) I guess they adjust the gearing/ rearsprocket to compensate for the differing wheel sizes. The LBS has agreed a small discount on the RRP.

 

[Nealh]

The only problem with hubs gears is they straight away make the use of very good rear motor hubs non viable.

 

[vfr400]

especially when we all know that the derailleur loses efficiency when it gets dirty and when using gears at the extreme ends of the cassette.

I think that I can say that you're categorically wrong because we can't all know that if I don't/didn't. Have you got any evidence to support that? Who else knows about it? How far off centre gives how much reduction in efficiency? Does it only affect the modern 12-speeds, or would it happen on a 3-speed cassette?

I've never adjusted, cleaned nor lubricated the derailleur on my road bike in 2000 miles. Do you think I'll be able to pedal up hills more easily if I get some soap and water on the derailleur? Do I need to polish it with Brasso too? Would I be able to get up hills more easily if I changed to a 5 speed cassette that's narrower because I nearly always use bottom gear when climbing, or does it happen on the extreme ends regardless of the number of gears - maybe something to do with air resistance or something?

I think most would agree that chains are more efficient when they're cleaned and lubricated, but both hub gears and derailleur gears use chains. Is it that derailleur chains are longer? Perhaps the same amount of dirt spread over a longer chain means less dirt per link and therefore less dirt on the part of the chain that's engaged with the sprockets, so wouldn't that make it more efficient than the shorter hub gear one, not less efficient.

This is what Sheldon Brown says about chainline in relation to efficiency, though he doesn't cite the research, nor quantify "minor", so I can't say that he's right or wrong. I can see the logic, but the question is to what degree is efficiency lost? I think that he's implying that it's a negligible affect, just something to be aware of in case you have an extreme case of misalignment.
"research has shown the loss to be minor, at least with modern, flexible chains."

Genuine research here says that the biggest factors affecting the drive train efficiency are sprocket size and the amount of tension in the chain. Higher tension gives greater efficiency, so that implies that a derailleur would be more efficient due to the higher chain tension provided by the spring in the derailleur unless you have a sprung tensioner on your hub gears. The video is interesting. It shows virtually no energy being wasted on the derailleur compared with the drive sprocket.

Headlines@Hopkins: Johns Hopkins University News Releases

 

[culy30]

The attached technical journal published in 2001 covers the gear efficiency subject comprehensively.

Personally I tend to clean my drive train very frequently, certainly before and after any events I ride and most weeks when I'm just riding/training, especially in winter. With transmissions costing over a grand maintenance is part of my way of life and its been this way for over 30 years. I have a power meter on my road bike and anecdotally I do notice the difference between a newly cleaned and lubricated drive train and one coated in mud and grit. Not only are gear changes quicker on a clean transmission, I can actually hear and feel the difference.

I'm not sure if the attached will change anyone's world, but its interesting to have some scientific findings on the subject.

 

[vfr400]

The attached technical journal published in 2001 covers the gear efficiency subject comprehensively.

Personally I tend to clean my drive train very frequently, certainly before and after any events I ride and most weeks when I'm just riding/training, especially in winter. With transmissions costing over a grand maintenance is part of my way of life and its been this way for over 30 years. I have a power meter on my road bike and anecdotally I do notice the difference between a newly cleaned and lubricated drive train and one coated in mud and grit. Not only are gear changes quicker on a clean transmission, I can actually hear and feel the difference.

I'm not sure if the attached will change anyone's world, but its interesting to have some scientific findings on the subject.

That was very interesting reading. One thing not obvious. It shows that you get a slight increase in your pedalling efficiency when you use a crank-drive bike compared with a hub-motor because of the additional chain tension. That was also implied from the research that I linked to above.

I can imagine that derailleurs have now pulled out an even bigger advantage. That was done in 2001 using a basic Shimano 27 speed system. The efficiency of the modern two-chainwheel 24 speed systems are clearly leaps ahead, while as I doubt that the hub-gears have changes significantly.

One thing's for sure. If hub gears were fantastic, they'd use them in the Tour de France and other cycling competitions where everyone is trying to eek out the last .001% of efficiency.

 

[Woosh]

One thing's for sure. If hub gears were fantastic, they'd use them in the Tour de France and other cycling competitions where everyone is trying to eek out the last .001% of efficiency.

there is still the weight factor to consider.

 

[KirstinS]

I only really interested in mtb and utility cycling. Totally agree hubs gears are not the answer for speed , professional, weight weenie types.

However I have had alfine 8 hybrids (chained and shaft drive) as well as my current fav a bbs converted Ti hardtail. Also with alfine

Unlike my deraileur bikes it has never skipped a gear or slipped a gear under load, failed to change without a extra mini press. I can change several gears at once if I wish (or make a mistake ). Change stationary etc

I love that hard tail and have done many miles over south downs . I've no issue whatsoever changing gears on hills. And never had

Having said that my bike is light and I'm 68kg so maybe that helps alleviate

 

[culy30]

I only really interested in mtb and utility cycling. Totally agree hubs gears are not the answer for speed , professional, weight weenie types.

However I have had alfine 8 hybrids (chained and shaft drive) as well as my current fav a bbs converted Ti hardtail. Also with alfine

Unlike my deraileur bikes it has never skipped a gear or slipped a gear under load, failed to change without a extra mini press. I can change several gears at once if I wish (or make a mistake ). Change stationary etc

I love that hard tail and have done many miles over south downs . I've no issue whatsoever changing gears on hills. And never had

Having said that my bike is light and I'm 68kg so maybe that helps alleviate

Indeed it seems to Hub gears are more about lower maintenance and simplicity of use (albeit that the internals are complex).

 

[culy30]

there is still the weight factor to consider.

And it doesn't stop there. I found this article which looks at lubrication and gear choice vs efficiency. Published 19 years ago mind.

 

[flecc]

One thing's for sure. If hub gears were fantastic, they'd use them in the Tour de France and other cycling competitions where everyone is trying to eek out the last .001% of efficiency.

I fully agree with all your previous posts on this subject.

One factor often ignored, including in those tests at one standard speed, is how each type of gear is preferred. Hub gears have usually been preferred in utility riding which is generally at much lower speeds, ambling around at 10 to 12 mph being commonplace. With much lower effort required that makes efficiency far less important.

Much more important to utility riders is low maintenance and long term reliability. Hub gears used at lower speeds with less inputted effort do have a clear advantage there, since they can often last well over a decade of continuous use without any attention. The wider chains and sprockets generally used adds to the low maintenance advantages. Hub gears also have the advantage that chaincase protection and even immersion lubrication in some instances can make chains and sprockets last almost indefinitely.

So for speed and high load applications, derailleur every time.

But for everyday utility use with moderate effort at reasonable cycling speeds, hub gears have the overall advantage.
.

 

[culy30]

I fully agree with all your previous posts on this subject.

One factor often ignored, including in those tests at one standard speed, is how each type of gear is preferred. Hub gears have usually been preferred in utility riding which is generally at much lower speeds, ambling around at 10 to 12 mph being commonplace. With much lower effort required that makes efficiency far less important.

Much more important to utility riders is low maintenance and long term reliability. Hub gears used at lower speeds with less inputted effort do have a clear advantage there, since they can often last well over a decade of continuous use without any attention. The wider chains and sprockets generally used adds to the low maintenance advantages. Hub gears also have the advantage that chaincase protection and even immersion lubrication in some instances can make chains and sprockets last almost indefinitely.

So for speed and high load applications, derailleur every time.

But for everyday utility use with moderate effort at reasonable cycling speeds, hub gears have the overall advantage.
.

I fully agree in principle, however having thought about this, surely riding at lower power outputs means that efficiency has a larger effect on speed. If say 25watts is need to overcome resistance, then a rider pedalling at 125Watts will lose 20% of his power, whereas a rider pedalling at 250Watts only loses 10%? Does that make sense? I'm not sure. It may be that only 10watts is lost, but the same principle applies.

I found this article which appears to support this theory.


"The numbers are going to be a little different for everybody. But the difference in time actually gets greater with slightly less power (to a point).

If we run the numbers using an average between the 50-200w for interests sake (125w), we get ~93% efficiency on the Rohloff and ~88% with the Pinion (which is a 6w difference... it would actually be a little less due to idle losses). Anyway, that's a 4 minute 34 second difference on the flat over 100km with the same rider as in the example above (2.0% slower). On the hilly course, the difference between a Rohloff and Pinion is 7 minutes and 22 seconds (2.7% slower)!"

So if anything, riding at less power may make a larger difference in terms of time!https://www.cyclingabout.com/speed-difference-testing-gearbox-systems/

 

[flecc]

I fully agree in principle, however having thought about this, surely riding at lower power outputs means that efficiency has a larger effect on speed. If say 25watts is need to overcome resistance, then a rider pedalling at 125Watts will lose 20% of his power, whereas a rider pedalling at 250Watts only loses 10%? Does that make sense? I'm not sure. It may be that only 10watts is lost, but the same principle applies.

I found this article which appears to support this theory.


"The numbers are going to be a little different for everybody. But the difference in time actually gets greater with slightly less power (to a point).

If we run the numbers using an average between the 50-200w for interests sake (125w), we get ~93% efficiency on the Rohloff and ~88% with the Pinion (which is a 6w difference... it would actually be a little less due to idle losses). Anyway, that's a 4 minute 34 second difference on the flat over 100km with the same rider as in the example above (2.0% slower). On the hilly course, the difference between a Rohloff and Pinion is 7 minutes and 22 seconds (2.7% slower)!"

So if anything, riding at less power may make a larger difference in terms of time!https://www.cyclingabout.com/speed-difference-testing-gearbox-systems/

True enough and I was already well aware. But in practice utility riders don't worry about such minutiae, they usually just ride at the speed and effort levels they are comfortable with. They don't care if it's a mile or two per hour slower and cycling in The Netherlands where hub gears are very popular illustrates this very well.

I'm old enough to remember when it was the same in Britain and when my boss in the trade snorted in derision at the first deralleur we saw in the shop, saying, "Ridiculous, who would ever need more than three gears".
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Continental Bicycle Systems - Drive Units

With the 48V Revolution, our system encompasses a world-first innovation.

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that has the gears inside the motor

 

[Woosh]

that has the gears inside the motor

That's the best place for it.

 

[flecc]

That's the best place for it.

Just a pity it's the inefficient NuVinci system.
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