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• Hub motors and mid-drive motors on electric bicycles – What’s that all about?

One of the most common questions that prospective buyers of electric bicycles have, is whether to ‘go mid-drive or hub drive’. Even people who don’t think to ask such a question are often bombarded by friends, sales people, manufacturers etc about which is better. What is it that they’re all on about and why is it even a thing? Do we really have to learn all that technical jargon to buy a good e-bike? Probably not, but knowing what your options are is important, particularly as you will not always be presented with all the options when you walk into a shop, unless it’s a true e-bike specialist, so make sure you get the chance to consider everything available to you before you make a decision. In most areas in NZ, this will mean visiting more than one shop.

Background Reading

Two years ago, we wrote an article about the benefits and drawbacks of the main motor placement options on electric bicycles, (re-published on our domain here) and now is a good time for a re-cap. The original article speaks in technical terms on the consequences of each motor placement option and therefore the pros and cons for the owner of the bike.  In this article, we will focus more on the non-technical side of it all. Well, I’ll try anyway, but you’ll still come across a lot of terms in here that are found in our Glossary or FAQ.

What are the options?

There are two general categories of electric bicycles for sale in NZ (and Australia, U.S. and many other places).

1 – “Hub-motor e-bikes with throttles” such as eZee Sprint, Magnum Metro and many more. These e-bikes are often from specialty e-bike companies as opposed to established bicycle manufacturers.

2 – “Mid-drive e-bikes”, eg e-bikes equipped with the motor drives by Bosch, such as Gepida, Moustache e-bikes, Riese and Muller and many more. European e-bikes are highly represented here, though there are plenty of factory generic options coming through as well.

It’s a lucky thing e-bikes are inanimate objects, as generalisations on these categories are unavoidable. And although there are always exceptions, the generalisations are definitely useful:

The hub motor category is more transport-oriented and excels in the nuts and bolts of transport – they go faster, have bigger batteries and are more affordable. The geometry and sizing is usually more ‘shareable’, fitting a variety of people. They almost always have throttles and cadence sensors, though the use of torque sensors in this category is growing. The bikes hold a bit more mass-market appeal, more likely to be built with function over form and don’t generally target the existing cyclist market.

The mid-drive category is almost synonymous with the european market, for reasons we will get into later. The choices in this category are more like non-electric bicycles in many ways, including aesthetics, geometry and sizing, ride feel and component choice. These are generally made by existing bicycle manufacturers who have a ‘bike first’ design philosophy, prioritising the non-powered nature of the vehicle over things like battery size, power, top speed etc. These bikes almost never have throttles and almost always have a torque sensor to help the bike know when you want power. They are generally slower, with most not giving assistance above 25kph. However, that is very quickly changing with more available at 32kph and 45kph.

Which option is the best?

You probably know I’m not going to answer that, they’re both great options and the beauty is that they are very different to one another. For an MTB rider that plans for both wheels to leave the ground at the same time, we will generally recommend a mid-drive. For an everyday rider who wants to do the occasional wine trail, the case for the hub drives is very strong, though plenty of people will prefer a mid-drive too.

I stick to the original article’s advice that you need to ask yourself (and your supplier) the following about any bike you’re considering.

1 -Do you feel confident when leaving the house on this e-bike, that you’ll have an enjoyable and safe ride that will make you want to use it next time you leave the house?

2 – Do you feel comfortable riding this electric bicycle?

3 – Can the electric bicycle go up hills with an amount of assistance sufficient to your needs/desires?

4 – Can someone service this electric bicycle for you, are spare parts available now and will spare batteries be available in 5 years?

What are the latest trends in the technology – why can’t one system have it all?

Since writing the original article, what’s changed in two years? Well, nothing that makes any of the original information inaccurate. However, there have been changes to what’s commonly for sale. In particular, there are many more hub motor e-bikes available with torque sensing systems, which was previously the domain of mid-drive e-bikes. And vice versa, there are many more mid-drive e-bikes available that can go faster than 25kph, previously the domain of the hub-motor bikes. This blurring of boundaries will make it even harder to draw any useful generalisations and therefore a little harder to decide in one sitting at your computer which bike to buy! However, deciding what to buy before you’ve ridden it never was a good idea. In reality these extra options mean it’s easier than ever to find an e-bike that you love, you may just find there’s a few more on your list to test ride than you first thought!

Bikes like the T4 torque sensing series of eZee bikes (Sprint Alfine T4 etc) are truly a ‘best of both worlds’ situation, with power in proportion to your pedalling achieving a smooth, natural ride, but still with the big batteries and heaps of power to go up any hill and higher top speeds.

Then we are also seeing the mid-drives offer higher speeds, with 32kph becoming an option for many brands, notably on most Shimano bikes since 2017 and some Bosch bikes from 2018. They still don’t have throttles and huge batteries, but for someone who wants to do most of the pedalling work but wants to go quicker than 25kph, this is also a ‘best of both worlds’ offering. It truly is exciting times for e-bike shoppers!

Why can’t one bike have it all and we can do away with these divisions? Some constraints certainly are artificial, such as a speed limit imposed in a different continent affecting what you can buy today, that’s a solvable problem. But other constraints are real – why do the e-bikes that feel most like a bike, not perform as well on the electric side? Because they’ve got a lower weight and space budget for robust motors and large batteries! Why do they cost more when they try to cover all bases? Because they’re having to spend more to accommodate competing interests. Evolving technology can cover some of these issues (eg lighter battery cells), but some are fundamental questions about what’s most important to you. Upright bikes are more comfortable but they’re less aerodynamic and are less suitable for swerving downhills on windy tracks – that’s a fact of physics and technology won’t change that. When riding on Tāmaki Drive shared path and getting buffeted by wind over a bridge, a heavy-set e-bike is your friend, but you won’t feel that way if you try to lift it onto a poorly designed car rack – technology won’t change that either (though a better car rack will).

There is a reason after all, why there is more than one bike to choose from! Take advantage of that fact and choose one you’ll love!

Further reading – Why do these different categories even exist?

The first thing to consider to understand all of this, is that NZ and Australia are small markets for bikes of any sort, due to small populations and a near-total decimation of livable cities in favour of car traffic. Now that the public is interested in buying e-bikes, we’re in the nice position of being able to choose from many different options that have been developed elsewhere for decades, so we get to skip straight to the state of the art without ever having put up with lead acid batteries, <10km battery range etc. All respect to the pioneers of e-bikes from the local early adopters, the NZ companies and the international companies that sold into NZ for the last 10 years, but the reality is that what is available to an NZ consumer right now is almost completely based on what has been popular elsewhere in the world and which of those happen to be pretty good matches for what’s appropriate to sell in NZ. And the availability of bikes elsewhere in the world has been influenced by user demand, technical constraints/achievements and the local regulatory conditions (ie what was legal and what wasn’t). The story of each market around the world over the last few decades is very interesting, but this has already gone on for too long. So we will look at Europe and the sector that I would call ‘the internationals’ as they have been the ones that kiwis have been buying from. The european market is based on what kinds of e-bikes the european bicycle companies were making for their own market. The ‘internationals’ is about what e-bike companies were making and attempting to sell all over the world, including NZ.

1 – The European experience and the birth of the mid-drives

The e-bike industry in Europe was an add-on to the bicycle industry on both the consumer and supplier side. That is to say that the consumers were generally people who wanted to keep doing things that were normal for them to do on a bicycle, but with electric assistance (Japan is the same in this regard). This meant the original market was for older people or anyone who needed motor assistance to do what other people were doing without motors. E-bikes were made therefore to be ridden alongside other established bicycle infrastructure and designed to behave like other bikes in speed, acceleration, weight etc. The buyers themselves were generally experienced in riding bicycles. The industry making the e-bikes were world experts in making non-electric bicycles and therefore offered all the same frame size options, geometry, slick aesthetics etc on their e-bikes as they did on their non-electric bikes. As a result, the bikes had small batteries and motors, weren’t intended to go very fast and not generally intended to do anything you wouldn’t do with a non-electric bike. The legislation forbid throttles and didn’t allow motor assistance past 25kph. Was everyone happy with this? Not at all, there were many pushes for faster e-bikes for more motor assistance and other obvious possibilities for an electric bicycle. This push generally came from hillier cities and places where bicycles and bicycle infrastructure was not as well established, as their needs were different. However, there was sufficient numbers of buyers in areas that were flatter and had existing riders, that a huge industry blossomed, with the Netherlands being the clear leader per capita and the Germans leading on absolute numbers. This market started with hub motors, but the market share is being overtaken by mid-drive motors, which do a better job of mimicking a non-electric bike. These are fantastic electric bicycles, we stock a range of them and recommend very highly that you try some and if it’s for you, you’ll be pleased as punch. However, we do not prescribe to the commonly espoused view that this is the ‘best’ category and that the only reason to buy from the hub motor category is for value for money reasons. That’s a narrow view of the market, based on an assumption that all e-bike owners want their e-bike to be just like their non-electric bicycle (only better) and generally is held by those who only sell European bikes or who are only reluctantly offering electric bikes, viewing them as some sort of compromise to a ‘real bicycle’. It appears as a majority viewpoint, simply because those who currently have an opinion on the matter and the privilege to air that opinion are those who write magazines, work for established bicycle manufacturers or who are in some way or another, part of the existing industry, which is based on non-electric bicycles. So what about the majority then, the people don’t use non-electric bicycles anymore? Or those who do use non-electric bicycles but want an electric bicycle to be different, to allow them to do things they wouldn’t dream of doing on a manual bike?

2 – The internationals and specialist e-bikes

The international e-bike companies have been selling e-bikes around the world for as long as you care to guess, for example eZee since 2001 to Europe, the US, NZ, South Africa, Australia etc. The experience of these companies was to worry less about what the regulations were in every single country and think more about what kind of e-bike they wanted to make and then see who would buy it. Their strength was not in non-electric bicycles and neither was their interest. The priorities became the nuts and bolts of movement – how big a hill can you climb, how far can you go, what speeds can the bike sustain? The geometry and componentry was chosen around that – what sort of frame shape can fit a big battery and still hold a lot of cargo that e-bike riders will want to carry around? What shape is comfortable, stable, safe and suits a lot of people. Why make 7 sizes when most e-bikes will get shared around the household anyway, why not make it more versatile, prioritising the vehicle over the biomechanical efficiency of a particular rider? It is well worth reading the interview transcript with Wai Won Ching, CEO of eZee on this subject.

The challenges for these companies was finding markets to sell into that could sustain an industry. The Europeans ignored any market that wasn’t big enough to pique their interest and for a reason – it’s hard to make ends meet in a small market and they have easier options. The e-bike specialists on the other hand, only existed to sell e-bikes, hard work or not.

The USA became a good market for the internationals because of the accommodating legislation (32kph and 500W was allowed in most states, throttles were allowed) and although the bike riding conditions were poor, the total population was big. The US consumer was also less likely to be impressed that a bike was made in Europe and more interested in the performance of the vehicle.

Probably what is missing most was a clear marketing message. “Designed in <insert country> for <insert country> conditions” is about as imaginative as it gets, compared to the marketing budget of bicycle brands that sell more units in one single shop in a Dutch city than all the e-bike shops in Auckland sell put together.

Where to from here for NZ?

Time of course will tell. The market will never be big in global terms, but it is getting big enough for us to be able to buy whatever we want, instead of what just happens to be imported into NZ. International companies are competing for market share here.

The next big step will be seeing what, if any, guidelines and regulations the NZTA assigns to electric bicycles. Government regulation is a double edged sword. The dangers of over regulating are obvious – if great bikes for our market are declared outside of regulation, the industry will shrink and so will consumers options. However, practical and clear guidelines from government will give the industry more certainty in what to invest and import.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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FAQ and e-bike Glossary of Terms

Welcome to our Frequently Asked Questions and Glossary! Feel free to email in suggested topics/questions

Torque Sensor

A torque sensor is a device on an electric bicycle that measures how much torque the rider is exerting on the pedals. In other words, this allows the e-bike to know how hard the rider is pedalling. Generally speaking this means the bike is able to offer a smoother ride feeling, as it will give power proportional to how hard you are pushing, rather than giving a lot of power when you’re just on a flat. It also makes it less likely for the bike to take off when you didn’t want it to, as you generally only push hard on a pedal when you wanted to go forward! In the absence of a throttle, a torque sensor makes it easier to perform a hill start on an e-bike, as the bike can respond to your pedalling very quickly. Most e-bikes with torque sensors also have cadence sensors to help give the e-bike the full picture of what you are doing with your feet. However, generally people will just refer to the bike as using a torque sensor.

Cadence Sensor

A cadence sensor is a device on an electric bicycle that measures how fast you are pedalling. It is generally just used to decide whether you are pedalling or not. That is to say, it is rare to find an e-bike that changes how much power it gives you based on how fast you are pedalling, they simply have a threshold that you’re either above and therefore get power, or below and therefore get no power. The amount of power you get when you are pedalling will depend on the e-bike itself and what settings it has, but it will not depend on how hard you pushing on the pedals. For that possibility, the bike needs a torque sensor.

 

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Mid-Drive, Front Hub and Rear Hub Motor Comparison

Where’s the best place for the motor on an e-bike?

With more and more electric bicycles on the market in New Zealand, we’re seeing more examples of the various places a motor can be added to a bicycle. This article is about the advantages or otherwise of the three main motor placements on an electric bicycle. It is about ‘complete electric bicycles’, as opposed to electric bike conversion kits, which have slightly different criteria though a similar conclusion. Friction drives are ignored here, as are kickstarter/crowd-funded concept projects.

Spoiler alert – there’s no particular ‘absolute best’ place for a motor and there’s no ground-breaking technical information in this article. The usual common sense approach applies for anyone considering buying any given electric bicycle and it applies equally for battery placement, battery size, type of gears, frame type etc:

1 -Do you feel confident when leaving the house on this e-bike, that you’ll have an enjoyable and safe ride that will make you want to use it next time you leave the house?

2 – Do you feel comfortable riding this electric bicycle?

3 – Can the electric bicycle go up hills with an amount of assistance sufficient to your needs/desires?

4 – Can someone service this electric bicycle for you and are the maintenance requirements (both in cost and frequency of trips to the workshop) reasonable for your use?

5 – Are spare parts available now and will spare batteries be available in 5 years?

If the e-bike you’re looking at satisfies the questions above, then who really cares where the motor is? However, if you can’t happily answer yes to those questions above, then there’s probably a reason for that and motor placement might be one of them. Let’s dive into the different motor types. They all have their pros and cons, so the way to make this article useful is to consider each pro and con and ask yourself “how well does this benefit match my riding/lifestyle” and “how much will this ‘con’ affect me”.

Front Hub Motor – the sensible option

electric yuba mundo with ezee front hub motor

This is one of the simplest implementations of the electric bicycle. The motor is the hub of the front wheel, it turns the wheel over which then makes the bicycle move.

Advantages: Simple is good. This is very low maintenance as it shares the strain on the bike between the front wheel (motor power) and rear wheel (human power and rider weight). It also physically separates the motor system from the rest of the bicycle parts, making your bike easier to service and spare parts more aligned with conventional bike parts. Allows any type of gearing in the rear wheel, such as internal hub gears. No matter where the battery goes, you’ll end up with a well balanced and very stable bike.

Disadvantages: Front end of the bicycle becomes heavier, reducing choice of front forks and making it a little harder to lift up a curb or into some types of bike parking racks. Traction is an issue on very steep tracks with loose surface. Quick release front wheel not an option. Above a certain power level, front hub motor becomes unviable for various reasons such as fork strength. However, this article is not interested in e-bikes of that level of power and speed, it is focused on legal electric bikes.

Best suits City Riders. So what kind of rider or what kind of bike best matches up with the advantages on offer? A low maintenance and simple e-bike with good balance and internal hub gears is going to best suit ‘everyday riders’ who ride to get around the city with the occasional rail trail and just want a comfortable, safe and reliable e-bike. These riders don’t suffer much from the disadvantages either, being mainly on paved roads. For this person, some of the disadvantages are actually advantages – no quick release front wheel means less theft risk. And a heavy front end on a bike with ‘upright’ seating position isn’t a problem while riding and actually adds to stability. Another ‘sweet spot’ for these e-bikes is for commercial and fleet use, when predictable maintenance requirements and costs are paramount to the fleet’s success. Therefore a common choice for delivery e-bikes (eg Dominos Pizza in NZ and Australia), post e-bikes (this is what NZ Post and Australia Post use) and for e-bike fleets (Auckland Council, NZTA, Datacom and more).

Least Suits MTB Riders. Which kind of rider would not benefit from these advantages and would suffer most from its disadvantages? A mountain-biker. They are always riding on loose surfaces, their bikes are not ‘upright’, choice of high tech front forks is essential and a heavy front end when jumping over tree-roots etc isn’t going to work. Low maintenance isn’t essential to an MTB, they won’t want internal hub gears and with the rates of crashing their bikes, a trip to the shop every now and then is normal.

On the fence – Touring Riders. Electric bicycle touring riders are in between. They will encounter a variety of riding conditions where a heavy front end might be inconvenient. On the other hand, low maintenance and simple is paramount for long distance riders. The decision will be based on the likely terrain and will be some sort of compromise. I used an eZee Torq with front hub motor for the Perth-Sydney ride with mixed terrain and the eZee Forza with rear wheel drive for the Cape York-Sydney ride which was more heavily off road. Sam had both front and rear eZee motor on his eZee e-Rex fat bike on a trip through outback Australia.

Example of a perfect fit – the eZee Sprint city electric bicycle.

Rear Hub Motor – the Fun option

In reality there isn’t a huge difference between a front hub or rear hub motor electric bicycle. Both have similar performance, the motor has similar design constraints and both are very efficient in propelling the bicycle without a drive chain (direct to the spokes). The traction issue between front and hub motors is largely over-stated. And there is no difference at all in power/speed/efficiency whether the motor is pulling you or pushing you.

The real consideration for the buyer is a trade-off in maintenance/component choice vs the feel of the ride.

Above a certain power level, a rear hub motor is the easiest way to pack in a lot of power relatively safely without damaging the frame or causing the bike to slide out around corners. For this reason, electric motor bikes like the Stealth Bikes use rear hub motors. This is not particularly relevant to the kind of electric bicycles we sell (road legal ones).

Advantages – Light and maneuverable front end, allowing any type of front fork. All your weight is on the motor, giving it maximum traction even in adverse conditions. Aesthetic advantage of being able to conceal the motor among the gears, panniers bags etc. Even when the same hub is used, noise levels are lower on a rear hub, due to the extra weight on the wheel minimising vibrations and resonance through other parts.

Disadvantages – Choice of pedalling gears are restricted. In general, derailleur gears are the only option, and not internal hub gears. Rear wheel and spokes are under enormous stress – your weight, your pedalling power, the motor’s power, the motor’s weight and even the dimension of the motor make for a more difficult wheel build than a conventional bicycle hub. It is not unusual for electric bicycle with rear hub motors to break spokes regularly. Check carefully with your retailer whether or not replacing spokes will be considered warranty work or not and who will cover the cost if the wheel needs to be rebuilt completely in the first say 1 or 2 years. It happens a lot. The good news is that if a brand has sorted out all these issues, it’s unlikely to be a problem. But there are plenty of e-bikes on the market with rear hub motors that simply will not stand the test of time and distance.

Best Suits: Riders who will often go off-road on steep/loose tracks. Also city riders who are happy to prioritise the feel of the ride and accept higher maintenance on the rear wheel and weren’t going to choose internal hub gears in any case. It is best suited on high-end e-bikes where the rear wheels are built with high quality components and to a high standard of manufacture. If you’re going for a super low budget, go for a front hub motor instead.

Least Suits: Any owner for whom maintenance is a priority including fleet operators.The combination of more motor wheel maintenance, plus no option for internal hub gears will mean overall increased maintenance. Note that rear wheel drive bikes are easier to sell in general, so you see more of them. Unfortunately this means there are a lot of cheaper electric bikes with rear hub motors where it’s only a matter of time before the spokes start breaking and expensive and lengthy work is required. The heavier the motor and the heavier the rider, the more of a problem it will be.

Mid-Drive Motors – the ‘have it all (almost)’ option

Mid-drive motor systems on electric bicycles from German manufacturers such as Bosch and Impulse have started to become more common in the Australian and NZ market. This list is growing, with Shimano STEPs, Yamaha and Brose all in on the action. This option is very different to the hub motor setup. The mid-drive motor pulls on the chain, just as your pedalling power does. This then turns the rear wheel and away you go. The motor’s drive goes through the bicycles gears, so the motor is effectively geared too.

Advantages: Allows both wheels to be ‘normal’ bicycle wheels, giving all the available options of quick release, internal hub gears etc. Front forks can be any type and both front and rear end of bike is kept light. Centre of gravity is low and the whole e-bike is usually a little lighter too. The drive is via the rear wheel, so traction is not an issue. Rear wheel spokes are not stressed as much as on a rear hub motor setup because the motor’s weight is not back there and the wheel build is not affected. Motor is geared, so going slow and steady up very steep hills is achievable. You can also have internal hub gears in the rear, which otherwise only a front hub motor would permit.

Disadvantages: Higher Maintenance and no throttles. More complicated system, so motors are usually more expensive and the proliferation of sensors in the bike adds to possible failure modes. The drive-chain is under increased stress (human power + motor power through the one chain), so the chain, gears and rear hub will need to be maintained and replaced more frequently. The shifting is integral to the functioning of the e-bike, so your shifter cable and derailleur (or rear internal hub) need to be mechanically A1 at all times or damage can result. In general, these systems provide less assistance, so if you’re looking to minimise sweat, exacerbating knee/joint issues then test ride these thoroughly before making a purchasing decision – some are much easier than others to do a hill start or ride up steep hills.

Grey Area: There’s a lot of aspects on a mid-drive e-bike that are either advantages or disadvantages, depending on what you want from an electric bicycle. Make sure you try the bikes out and think about the 5 questions at the beginning of this article and make your choice. Are the following good or bad things for you:

– Motor replaces bottom bracket, providing an opportunity to measure the rider’s effort on the pedals and tuning the electric drive system to respond accordingly, making for a ride that feels more like riding a normal bike. This also means it forces you to do more work

– The motor is going through the gears, so you can change gear to keep the motor in its most efficient mode. But this also means you have to be in the right gear for the motor whenever you change speed/hills. More to do/learn

– At the moment (and this will change), most of these bikes are coming from Europe. This gives access to e-bikes of a higher standard of manufacture and finish than what we are often used to down under. This also means more scarce or expensive spare parts and usually the bikes are speed limited to 25kph and they usually don’t have a throttle.

– Longer range (km) per unit of battery capacity. For example a Focus Aventura e-bike with 17Ah battery will likely go further than a hub motor bike of the same battery capacity. But this also means that you’re doing more of the work which might be good or might be a drag.

Best Suits: Hands down the best system for expert MTB riding. Rear wheel traction but with good centre of gravity, lightweight wheels and any suspension option is possible. Also a good compromise for electric bicycle touring. Has rear drive traction, not too many rear spoke problems, often easier to ride unassisted than a hub motor e-bike. Not as low maintenance as a front hub motor but by carrying some spare chains with you and careful cleaning/maintenance it is completely manageable.

Also great for riders who want an electric bicycle to feel like their normal bicycle but with less hills, or perhaps less a few decades – still an effort to get around, but not painful. With this they also get the benefits of longer range and a lighter e-bike, often with a higher standard of finish/manufacture.

Least Suits: Riders who want as much help on the hills as possible and a throttle to get off at a start. This is particularly an issue for electric cargo bikes where the total weight of the bike + gear is higher and the size of the bike means that taking off in a straight line is so much easier with a throttle. Anyone living with M.S., Polio, Chronic Fatigue, Prosthetics and other conditions that affect balance and muscular control in the legs and core. Applications where budget for maintaining and replacing chains, cassettes, rear hubs etc is limited.