In recent years, dynamo hubs have become increasingly popular among bicycle tourists, bikepackers, commuters, and long-distance cyclists. This popularity can be attributed to improvements in efficiency and output thanks to advances in magnet technology, charging technology, LED light technology, and battery technology. Modern dynamo hubs can power a light that outputs over 1000 lumens or charge a phone, GPS, camera, or battery pack through USB. Of course, there are some drawbacks to using a dynamo hub. This guide answers the question: Are dynamo hubs worth it? I’ll list the pros and cons of dynamo hubs. I’ll also cover efficiency, cost, performance, maintenance, and much more. Finally, I’ll outline what to look for when buying a dynamo hub.
Table of Contents
- What is a Dynamo Hub and How Does it Work?
- Dynamo Hub Pros
- Dynamo Hub Cons
- Efficiency of Dynamo Hubs
- Power Output of Dynamo Hubs
- Dynamo Hub Drag
- Parts of a Dynamo Hub System
- How to Choose a Dynamo Hub
- Dynamo Hub Recommendations
What is a Dynamo Hub?
A Dynamo hub is a small electric generator that is built into the front hub of a bicycle wheel. As the bike’s wheel rotates, the dynamo in the hub generates electricity. You can use this electricity to power lights or charge small electronic devices like a phone, GPS, camera, or a small lithium-ion battery pack.
The hub wires directly to your dynamo headlight and USB charger. Installing a dynamo hub involves building a dedicated wheel around the hub. You’ll also have to wire in and mount dynamo lights and a USB charger. You can disable the dynamo hub when it’s not needed so it’s not always producing electricity and causing drag.
Dynamo hubs come in different power ratings. Which one you need depends on your power needs. 1.5 watt, 2.4 watt, and 3 watt hubs are available. They all run at 6 volts. The higher the wattage, the more power the hub produces. 3 watt hubs are the most common.
Most dynamo hubs produce AC power. For this reason, they are technically considered magnetos rather than dynamos. The AC power must be converted to DC to charge electronics. The USB charger converts the power. Lights can run on AC power.
How does a Dynamo Hub Work?
Inside of the dynamo hub, there are a series of small magnets mounted around the walls of the hub body. In the center of the hub, there is a coil of copper wire and a powerful stationary magnet. The large magnet creates a magnetic field. As the wheel spins, the small magnets on the hub body quickly rotate around the stationary magnet and coil. This produces an electric current in the copper wire.
The faster you ride, the faster the magnets spin and the more electricity the hub produces. How much electricity a dynamo hub can produce depends on a number of factors including your speed, wheel diameter, the hub’s power rating, and the design and efficiency of the hub. Some hubs produce more power than others. Some offer better efficiency than others.
Pros and Cons of Dynamo Hubs
Whether or not installing a dynamo hub is worth it depends on the type of riding you do, how long you ride, and how much power you need. In this section, I’ll outline the pros and cons of using a dynamo hub.
Dynamo Hub Pros
- You can charge your devices as you ride- If you install a USB charger on your dynamo hub, you can use it to charge your phone, camera, GPS, battery pack, eReader, headlamp, and other small electronic devices. Whenever your wheels are turning, your device charges. This comes in handy for bicycle tourists and bikepackers. If you spend at least 3 hours per day in the saddle while touring, you can easily keep all of your devices charged.
- Your lights always work- Most bike lights rely on batteries. The problem is that you have to remember to charge or change the batteries periodically. They can also go out unexpectedly during a ride. With a dynamo hub, your lights always work. The LED lightbulbs last decades. You’ll never get stuck in the dark. This is a great feature for commuters. Your lights are always ready to use when you need them. It’s one less thing to worry about.
- Better lighting- Dynamo-powered headlights typically provide more light than battery-powered headlights. Many models output 1300+ lumens. The lighting is also better. Dynamo lights provide a wide field of light with even near-field and long-distance illumination. This gives you an excellent view of the road. Your headlight also doesn’t blind drivers, pedestrians, and other cyclists. Some lights even self-adjust as your speed increases. Lighting can be optimized for on or off-road riding. Battery-powered headlights, on the other hand, tend to produce a more narrow beam that is more focused in one place. For some comparisons between battery and dynamo-powered headlights, check out this excellent guide from Peter White.
- Low maintenance- Dynamo hubs are designed to be nearly maintenance-free. After installation, a high-end dynamo hub can run for tens of thousands of miles before it needs to be serviced. For example, the recommended service interval for a Schmidt SON dynamo hub is 50,000 km (around 31,000 miles). Lower-end models tend to fail sooner. You may only get 5,000 miles or less out of a cheap dynamo hub before it needs to be replaced or serviced. There is really no maintenance for the user to do.
- Dynamo hubs can save you time- Because you can charge your devices while you ride, you never have to sit around a power outlet waiting for your batteries to charge. This allows you to spend more time riding. For this reason, dynamo hubs are ideal for long-distance Randonneur riders and endurance racing. Competitive riders can’t afford to spend time waiting around for batteries to charge.
- You can use your devices all day without worrying about finding a place to charge- With a dynamo hub, you can leave your phone on at all times and use it for entertainment or navigation. You can use battery-intensive apps such as Strava to track your ride. Alternatively, you can use your GPS all day. You can also use your camera as much as you want. You don’t have to worry about your batteries dying mid-day because you can just plug your device in when you run low on power. For this reason, dynamo hubs are great for bicycle tourists and bikepackers who travel through rural and undeveloped areas where electricity is hard to come by.
- They work in all conditions- Dynamo hubs offer incredibly reliable power production. It doesn’t matter if your wheels are caked in mud or dirt. It doesn’t matter what the weather is like. Dynamo hubs produce power when you ride, regardless of the conditions.
- The drag is not noticeable- When you turn a dynamo hub with your fingers, you will feel some notchiness. Some cyclists worry that the drag produced by a dynamo hub will make the bike feel sluggish. This isn’t the case. Even though dynamo hubs do create some resistance, you won’t feel it when riding. I have accidentally ridden with my light on for many miles without even noticing.
Dynamo Hub Cons
- Dynamo hubs create resistance- As the magnets rotate around the coil, they produce drag. This drag is caused by the resistance between the small magnets and large stationary magnet as the poles repel one another. You are essentially paying for the electricity that the hub produces by sacrificing some pedaling power. For example, to charge a phone through USB, a dynamo hub will cost you somewhere between 4.5 and 12 watts of pedaling power depending on your speed and the efficiency of the hub. To power a headlight at the maximum brightness, a dynamo hub will cost you around 5-25 watts of pedaling power. With an efficient hub, this may only be around 5% or less of your total pedaling power. Powering a bright headlight with an inefficient hub could take up to 20% of your pedaling power. That is significant! You will feel this amount of drag while riding.
- Dynamo hubs reduce your pedaling efficiency and slow you down- The added resistance of the dynamo hub causes you to burn more energy while riding. You’ll ride at a slightly lower average speed as well. If you’re touring, you won’t be able to cover quite as many miles each day because you’ll tire out sooner and ride slower. An efficient hub will slow you down by an average of around 0.5-1 mph or about 5 minutes over the course of a 100km ride. A less efficient hub will slow you down even more.
- Dynamo hubs create some drag when not in use- The drag depends on the model of the hub and your speed. When your light is turned off and you’re not charging anything, a dynamo hub typically creates around 1.25-6 watts of additional drag. Admittedly, this is pretty minimal but it does add up if you cycle long distances. It’s also an unnecessary waste of energy if you don’t use your dynamo hub often. To compare, a non-dynamo hub creates around 0.5 watts of drag.
- Dynamo hubs don’t work well at low speeds- If you’re averaging less than around 7 mph or 12 kph, most dynamo hubs won’t produce enough power to charge a power-hungry device like a smartphone. Most phones need around 2.5 watts to begin charging. Most dynamo lights need around 3 watts to shine brightly. At these low speeds, most dynamo hubs produce less than 2 watts of power. Efficient dynamo hubs can charge small devices such as a GPS tracker or small battery pack at speeds as low as 3 mph or 5 kph but may not be able to charge a phone or power a light until you reach about 12 kph.
- Dynamo hubs are complicated to install- To install a dynamo hub on your existing bike, you’ll have to first build a new front wheel around the dynamo hub. This involves buying a rim and spokes and either building your own wheel or paying someone else to do it for you. You could also buy a pre-built wheel with a dynamo hub already installed. Next, you have to wire in your dynamo light and USB connector. This requires wire cutters and connectors. For some instructions, check out this guide. Of course, you could always just pay a bike shop to install the system for you. Also, this is a job you only have to do once. After it’s installed, you never have to worry about it.
- Complicated maintenance- Dynamo hubs require proprietary tools to service. They also contain delicate electronics and precision-made parts. It would be easy to cause damage if you don’t know what you’re doing. For this reason, some dynamo manufacturers recommend that you ship the hub to their service center for maintenance. This isn’t that big of an issue because dynamo hubs require such infrequent maintenance. High-end models can run go for 10s of thousands of miles before they require any service.
- Dynamo hubs are Expensive- Entry-level dynamo hubs cost around $60-$100. High-end dynamo hubs cost around $300-$400. A headlight will cost around $40-$100. A USB charger costs around $60-$220. You may also have to pay to have a wheel built with the dynamo hub. If you’re not comfortable working with electronics, you may have to pay someone to wire in the light and USB charge outlet. This could cost around $100 in labor. All in, you’re looking at spending $200-$900 to buy and install a dynamo hub depending on the quality of components and the amount of work you can do by yourself.
- Dynamo hubs add weight- Dynamo hubs weigh more than regular hubs. The magnets, coil, and electronics all add weight. For example, the SON 28 hub dynamo weighs 448 grams (15.8 oz). A regular Shimano XT front hub weighs 167 grams (5.9 oz). In this case, the dynamo hub weighs 281 grams (9.9 oz) more than the standard non-dynamo front hub. The extra weight reduces your efficiency slightly because it takes more energy to spin the heavier hub up to speed. Your wheels are one of the worst places to add weight to your bike.
- More complex- A dynamo hub adds a complex precision-built electronic device to your bike. If something fails and the hub stops producing power, you can’t just open it up and fix it. In fact, most dynamo hubs are completely sealed and are not designed to be opened by the user. If the hub stops working, you’ll have to ship it to the manufacturer for repairs or buy a new one. Of course, if the generator breaks, chances are the wheel will still roll just fine.
- Harder to remove and replace the front wheel- Every time you remove your wheel, you have to disconnect the dynamo hub. This involves unplugging a spade connector. When you replace your wheel, you’ll have to plug the connectors back together. This is just a minor inconvenience but can be pretty annoying when your hands are cold or when you’re trying to remove your wheel in the dark. The Schmidt SL connector design solves this problem. I’ll talk more in-depth about connectors later.
- Dynamo-powered light illumination changes as your speed changes- When you speed up, the light gets brighter and when you slow down, the light gets dimmer. This can be annoying if you have to ride slowly through a dark area. To solve this problem, some dynamo-powered headlights are designed to light up the road near you at slow speeds. As your speed and the illumination increases, the light shines further ahead. Also, some light and dynamo combos perform better at low speeds than others. When buying a dynamo light, you’ll want to consider how much power it requires and how much power your hub produces.
- You probably can’t charge your laptop with a dynamo hub- These days, most bicycle tourists and bikepackers like to carry a laptop while touring. Unfortunately, dynamo hubs do not produce enough power to charge laptops. 2.5 watts just won’t cut it. Many laptops need at least 30-45 watts to charge. There are a couple of solutions. You may be able to charge a large portable battery with your dynamo hub then charge your laptop from the battery. This is inefficient because some power will be lost when moving from the hub to the battery to your laptop’s battery. Another option would be to use a small tablet instead. Most small tablets will charge at 5 watts. The only other option is to only charge your laptop when you have access to a wall outlet.
- Some dynamo-powered lights go off when you stop- This is annoying if have to stop in a dark area to repair a flat. You might want to bring a flashlight or headlamp with you just in case. It’s important to note that this is only the case with older or lower-end models. Some models even flicker a bit when you’re riding at low speeds. Newer dynamo lights have a capacitor inside that charges up as you ride. This powers the LED lights when you stop. These are often called ‘standlights.’ With a standlight, your light will stay on for around 5 minutes after you stop. The capacitor charges up pretty quickly as well. If you commute in stop-and-go city traffic, you’ll want to make sure your light has a standlight.
- You might not be able to use a dynamo on steep hills- While charging a power-hungry device, the hub may create just enough extra resistance that you can’t climb up a steep hill. You may need slightly lower gearing to climb with a dynamo hub while charging. Another problem is that if you’re riding too slow up a hill, your device won’t charge. You may have to unplug your device until you reach the top of the hill. This can be annoying while riding through hilly terrain because your device will constantly stop and start charging. A buffer battery can help with this.
Dynamo Hub Performance
Not all dynamo hubs are equal. Some put out more power, offer better efficiency, or create less drag than others.
Dynamo Hub Efficiency
A dynamo hub converts your pedaling power into electricity that you can use to power lights and your electronic devices. Not all of the energy that you put into the hub gets converted into electricity. Some is lost to friction in the hub and resistance from the magnets.
Some dynamo hubs operate more efficiently than others. You can calculate how efficient a hub is by comparing the power output and the drag that the hub creates at different speeds. The more efficient the hub, the more pedaling power it converts into electricity.
This article from Cycling About does an excellent job of showing the efficiency of different hubs through lab testing. For example, it shows that one of the most efficient hubs, the Schmidt SON28 puts out about 3 watts of power but causes 5.5 watts of drag at 20 kph while using a USB charger to charge a device. This means that of the drag that the hub creates, about 55% goes into charging the device. The other 45% of the power put into the system is lost. An average cyclist can maintain 100-200 watts of power. If you’re producing 100 watts through pedaling, about 5.5% of your energy is going toward charging your device in this example.
A comparable but less efficient hub, the Shimano UR700, puts out about 4 watts of power at 20 kph but causes about 10.5 watts of drag. This means only about 38% of the drag goes toward charging your device.
The exact efficiency of a dynamo hub varies greatly. It depends on a number of factors including your speed, the type of light you’re using, the devices you’re charging, your weight and the weight of your bike, wheel diameter, the terrain, and more. Dynamo hubs range somewhere between 20%-60% efficiency. Most hubs run at their maximum efficiency when you’re riding around 20-25 kph (12.4-15.5 mph).
Dynamo Hub Power Output
Dynamo hubs are rated for either 1.5, 2.4, or 3 watts. This output is measured at 20 kph. The power output of the dynamo hub changes as your speed changes. The faster you travel, the more power the hub can deliver. Power delivery also depends on the power demand of your lights and the devices that you’re charging.
Some hubs are capable of producing more power than others at a given speed. Most dynamo hubs are designed to output 3 watts of power at 20 kph. This is enough power to charge a phone or power a headlight. Higher-end hubs can deliver close to 4 watts at that speed.
Most dynamo hubs are capable of charging a phone through USB at speeds of 12-18 kph (7.5-11.2 mph) when paired with a good USB charger. Phones are usually designed to start charging at 2.5 watts. Most dynamo-powered lights reach their maximum brightness when you’re traveling at around 20 kph (12.4 mph). The light will illuminate at much lower speeds.
Some dynamo hubs are capable of outputting much more power than others, even if they have the same wattage rating. Some hubs can produce sufficient power at speeds well below 20 kph. For example, a lower-end dynamo hub might only output 1 watt at 15 kph (9.3 mph). This isn’t enough to charge a device or produce much light. A high-end hub with the same 3 watt rating might produce 3 watts of power at just 15 kph (9.3 mph).
One of the most powerful dynamo hubs currently on the market is the Shimano UR700. At 25 kph, it can produce a peak output of around 5.5 watts to a USB charger. To compare, the SON28 only puts out about 4.5 watts at that same speed.
Dynamo Hub Drag
Dynamo hubs create resistance, which slows you down. The energy isn’t free. You can feel this resistance when you pick up a dynamo hub and turn the axle with your fingers. The axle does not spin freely. It feels kind of notchy.
The notches you feel are the small magnets passing the large stationary magnet as the hub spins. The SON28 has 26 magnets inside. You’ll feel this notchiness each time a magnet approaches the pole of the stationary magnet inside of the hub. When magnet poles approach, they repel one another apart. This creates resistance. As the magnets pass the poles, they repel against each other and push apart. These forces almost cancel each other out but not quite. The resistant force is a bit stronger.
When you’re not charging a USB device or running a light with your dynamo hub, the resistance is minimal and you don’t feel any notchiness. Most dynamo hubs create 1-5 watts of resistance with no load depending on your speed and the quality of the hub. For example, one of the more popular hubs, the SON28, creates less than 2 watts of drag at 30 kph (18.6 mph).
When you connect a USB device to charge it or turn your light on, the resistance in the hub increases. The amount of drag this creates mostly depends on the power demand of the light you’re running or the device you’re charging. The design of the hub comes into play as well. Remember, some hubs are more efficient than others. Some create more drag than others.
For example, to produce enough power to charge a phone, a hub might cause a drag of 4.5-12 watts, depending on your speed and the efficiency of the hub. To power a bright headlight at its peak brightness, the hub might cause a drag of 18-24 watts depending on your speed and the efficiency of the hub.
Assuming you create 100 watts of power from pedaling, an efficient hub might only take around 5% of your pedaling power to charge a USB device. That’s not too bad. Most likely, you won’t even be able to feel that small amount of resistance.
An inefficient hub could take up to 10-20% of your pedaling power to run a power-hungry light on its brightest setting. That amount of drag would slow you down significantly. You will feel the resistance while riding.
Of course, even regular hubs create some drag. A high-quality hub that is properly maintained causes about 0.25-0.5 watts of drag depending on your speed. Drag increases at higher speeds. You can subtract this from the drag created by a dynamo hub. This will tell you how much drag you are adding by installing a dynamo hub to your bike.
To get an idea about how much different dynamo hubs will slow you down check out this article from Cycling About. According to lab testing, it was found that an efficient dynamo hub will slow you down by around 3-6 minutes over the course of a 100 km ride. When the hub is not in use, it will slow you down just 17-30 seconds. This means you’ll ride about 1.5-2.7% slower with a dynamo hub than without. For most riders, that’s pretty insignificant.
Parts of a Dynamo Hub System
When you buy a dynamo hub, usually you’re just buying the hub itself. In order to use it, you’ll need to buy some other components. The parts of a dynamo hub system include the hub itself, a dynamo light, a USB charger, electrical connectors for the light and charger. You might also choose to install a buffer battery.
If you’re planning on installing a dynamo hub on your existing bike, chances are you’ll have to buy each part separately. In this section, I’ll outline each part of a dynamo hub system and explain what to look for.
- Dynamo hub- This is the actual hub unit that includes the generator. Some popular brands include Shimano, Schmidt SON, Sturmey Archer, Shutter Precision, and KT. You’ll have to build a wheel around the dynamo hub. This involves buying a rim and spokes and building the wheel or having it built.
- USB charger- These units regulate the power the hub delivers to your device so it doesn’t cause damage by supplying too much voltage. USB chargers also convert the dynamo hub’s AC power output to DC power that you can use to charge your electronic devices. Some energy is lost during this process. The best chargers use software and hardware to maximize efficiency. The USB charger also includes the USB outlet where you plug your device in to charge. These usually mount on the frame, steerer tube, or handlebars.
- Dynamo light- Dynamo lights come in a variety of brightnesses and beam shapes. The output of light is measured in lumens. The brightness at a given distance is measured in lux. When choosing a light, you’ll want to consider how you’ll use it. Some dynamo lights are designed for off-road riding and others are designed for road riding. Off-road lights tend to make a symmetrical beam. On-road lights tend to have a beam that matches the shape of the road. Some dynamo lights offer different brightness settings, beam shape settings, and battery assist modes. Most dynamo lights are designed to be mounted at the height of the top of the front wheel, on the fork crown. Some are designed to be mounted on the handlebars. Most models are waterproof. Some dynamo lights also integrate the USB charger into the light. You have a lot of options to choose from. A few popular dynamo light brands include Busch+Mueller, Schmidt, Supernova, and Herrman
- Electrical connectors- You may have to buy connectors for your light and USB charger that match the connectors on your dynamo hub. There are two different connector types that are common. One is made by Shimano and the other is made by Schmidt SON. The connectors attach to the wires coming out of the USB charger and dynamo light then plug into the connector on the dynamo hub. Your connectors must match. They are not cross-compatible. You must disconnect these when you want to remove your front wheel.
- Buffer battery- This is an optional component. A buffer battery allows you to continue charging or powering your devices while you are riding too slow for your dynamo to provide enough power or while you’re stopped. This way, your device isn’t continuously receiving then losing power and cycling on and off. A buffer battery is nice to have but not absolutely necessary. The drawback of charging from a battery is that around 20% of the energy is lost. For this reason, the best buffer batteries are pass-through batteries. These can deliver power straight from your dynamo to your device when your dynamo is supplying enough power. They can charge with any extra power. This way, you aren’t wasting energy. Pass-through batteries are more expensive. Regular batteries can only charge or power your device. They can’t do both at the same time. Some dynamo USB chargers have a built-in buffer battery. Batteries with a capacity of 5000 mAH or less work best because they have low enough resistance for the dynamo to charge them easily.
How to Choose a Dynamo Hub
When choosing a dynamo hub to install on your bike, you’ll want to consider a number of factors including the type of devices you plan to power, your axle type, your brake type, spoke count, and the type of riding you do. Below, I’ll outline each point to consider when choosing a dynamo hub..
Dynamo Hub Power Output
Dynamo hubs output either 1.5 watts, 2.4 watts, or 3 watts. Usually at 6 volts and 0.5 amps. 3 watt dynamo hubs are by far the most common. The output is typically measured at 25 kph or 15 mph. A hub that is marketed as 3 watts will produce an output of at least 3 watts of power at 25 kph.
At higher speeds, the hub produces more power and at lower speeds, it produces less. For example, while speeding down a steep hill at 50 kph, you may see a peak output of 10 watts or more. While slowly climbing up a steep hill at 10kph, your hub might produce less than 1 watt of power.
If you typically ride at speeds lower than 25 kph (around 15 mph), you’ll want to choose a 3 watt dynamo hub if you plan to charge devices through USB. These hubs typically produce enough power to charge a phone starting at speeds as low as 12-20 kph (7.5-12.5 mph). Most bicycle tourists and bikepackers go with 3 watt hubs because they tend to travel at low speeds.
If you ride a bike with small 16-20” wheels like a folding bike, you may be better off with a 2.4 watt dynamo hub. You can get away with a lower wattage hub because smaller diameter wheels turn at a higher rpm to maintain the same speed as larger wheels. When running at a higher rpm, the hub produces more power. Also, a 3 watt hub may create too much resistance on a bike with small wheels.
If you typically ride at speeds above 15 mph (around 25 kph) and you only want to power your lights, you may be able to get away with a 1.5 watt dynamo hub. If you plan to power your electronic devices as well, you might prefer a 2.4 or 3 watt hub.
Dynamo Hub Electrical Connectors
Dynamo hubs connect to lights and USB chargers with a spade connector. There are two different connector designs on the market. One is designed by Shimano and the other is designed by Schmidt SON.
In terms of performance, they both work about the same. Both connectors transfer power from the hub to the light or USB charger. Because there are two competing connector designs, most dynamo light and USB chargers don’t come with any connector attached to the ends of the wires. This allows you to choose the connector type that you need for your hub. You must install the connector on the wires of your light and USB charger. You’ll probably need a wire cutter to do this.
There is a third connector design from Schmidt called Schmidt SL. With this design, the side of the dynamo hub forms its electrical connection with a plate that is mounted on the fork dropout. The plate is soldered to wiring that is built into the fork.
The benefit of this design is that you don’t need to disconnect any wires when you remove your front wheel. The hub automatically connects when it makes contact with the plate in the dropout. The drawback is that this setup requires a custom fork that is designed to work with the Schmidt SL system. Chances are, you would have to install a new fork. Most Schmidt SON hubs come in an SL version. FOr more info, check out this great guide.
Axle Type, Axle Diameter, and Hub Width
When choosing a dynamo hub, you’ll need to take your axle type, axle diameter, and hub width into consideration. Not all dynamo hubs are compatible with all bike frames. The hub needs to be designed for your specific axle type and hub spacing. Dynamo hubs are available in a range of different sizes to fit pretty much any bike.
A few common dynamo hub sizes include:
- 9mm x 100mm quick release- This size is common on older and lower-end bikes.
- 12mm x 100mm thru-axle- for road bikes
- 15mm x 100mm thru-axle- for mountain bikes
- 15mm x 150mm thru-axles- for fat bikes
- 9mm x 135mm quick release- for quick release fat bikes
- 15mm x 110mm thru-axles- for mountain bikes with boost spacing
In the list above, the first number represents the axle diameter. The second number represents the axle length. The hub width you need depends on your front hub spacing.
If you’re unsure about which size of hub you need, check out my thru axle vs quick release guide.
Number of Spokes
Dynamo hubs are available in a range of different spoke hole counts including 20, 28, 32, 36, and 48. Many lightweight road bikes and folding bikes use 20 or 24 spoke front wheels. Most mountain bikes and touring bikes use 32 or 36 spoke front wheels. Tandems and expedition touring bikes often feature 48 spoke wheels. The spoke count of the hub must match the spoke count of the rim.
The number of spokes plays a role in the strength and weight of the wheel. More spokes create a stronger wheel. Of course, the extra spokes also add weight. The spoke tension needs to be balanced across the entire wheel to ensure that the wheel stays true and strong.
For more in-depth info, check out my guide to 32 Vs 36 spoke wheels.
Dynamo hubs are available for both disc and rim brake bikes. Dynamo hubs for disc brake bikes have rotor mounts. Usually 6 bolt. Hubs for rim brake bikes do not have rotor mounts. For more info on bike brakes, check out my disc vs rim brake guide.
Dynamo Hub Recommendations
Dynamo hub options are pretty limited. Really, there are only a handful of dynamo hub manufacturers. The main ones include Schmidt SON, Shimano, Shutter Precision, KT, Sanyo, and Kasai. In this section, I’ll outline some of the best dynamo hubs available.
Schmidt SON Dynamo Hubs
Schmidt makes some of the most efficient and reliable dynamo hubs on the market. In fact, these German-made hubs are pretty much the industry standard these days. They offer excellent weatherproof sealing with high-quality SKF sealed bearings. These hubs can run for 50,000 km before they need servicing. They are also guaranteed for 5 years.
When it comes to performance, the Son28 offers incredibly low resistance while the hub is not in use. It produces less than 2 watts of resistance at 30 kph. When charging through USB or powering a light, the SON28 is also one of the more efficient hubs on the market. The drawback is that Schmidt SON hubs are some of the most expensive.
The Schmidt Son28 is available in both thru axle and quick release varieties for both disc and rim brake bikes. They are available in 28, 32, 36, 40, and 48 hole options.
Shimano Dynamo Hubs
Shimano is the largest manufacturer of dynamo hubs. They offer a wide range of options including some of the most affordable hubs on the market. Shimano dynamo hubs are also reliable, easily serviceable, and offer excellent performance for the price. In general, Shimano hubs are slightly less efficient than Schmidt SON. Shimano probably makes the best value hubs.
On the higher end, Shimano offers the UR700. This is one of the most powerful and efficient dynamo hubs on the market. It is a great choice for off-road riding or riding in hilly areas.
Shimano also offers a wide range of mid-range and lower-end dynamo hubs. On the lower end, they offer the Alfine and Nexus ranges. These hubs offer an excellent value with solid performance at a slightly higher weight than more premium hubs. They are slightly heavier than the higher-end Deore LX and Deore XT ranges. One of the more popular options is the Shimano DH-S501 Alfine.
Shimano offers both quick release and thru axle dynamo hubs in both disc and non-disc options. They offer 32 and 36 hole options. Because they offer such a wide range of hubs, you can find one to fit pretty much any bike.
Shutter Precision Dynamo Hubs
Shutter Precision offers some of the lightest dynamo hubs on the market. Their prices are also pretty reasonable for the quality that they offer. They are reliable and long lasting as well. The drawback is that Shutter Precision dynamo hubs don’t perform quite as well as comparable Schmidt SON or Shimano options. They are less efficient and output less power.
Shutter Precision offers both thru axle and quick release dynamo hubs with a wide range of spoke hole counts including 20, 24, 28 32, and 36 hole. For this reason, they are popular among road riders who use 20 and 24 hole wheels. They are also available in disc and non disc options.
Dynamo Hub Alternatives
Dynamo hubs aren’t the best choice for every cyclist. Some riders don’t want to deal with the added cost or complexity. Some don’t want to add weight and drag to their bike. Luckily, there are alternatives to installing a dynamo hub if you need electricity while you’re riding. A few options include:
- Solar panel and charger- Solar panels have become much more efficient over the past few years. It is possible to keep small devices charged with solar power these days. There are compact 28 watt panels available that you can mount on top of a rack and panniers. This BigBlue 3 (#ad) would work well. The benefit to using solar is that it doesn’t cause drag like a dynamo hub. Of course, you still have to carry the extra weight of the solar panel and charger. The panels are also bulky. They can cause wind resistance as well. The main drawback is that solar panels need direct sunlight to produce power. This makes solar systems a bit less reliable. On a cloudy day or while riding in the shade, it may not produce enough power to keep everything charged. You also have to keep the panel clean.
- Battery pack- A large portable battery can charge your phone, GPS, light, camera, and more without creating any additional resistance. A 10,000 mAH battery can charge a phone 2-4 times depending on the size of the phone’s battery. There are a couple of drawbacks. You still have to charge the battery. Every couple of days, you’ll have to find a place where you can sit down for a couple of hours while your battery charges. Large batteries are also heavy. This setup can work out great for day rides or short tours where you don’t need much power.
- Stopping to charge at power outlets- Of course, you can always simply rely on finding an outlet to charge your devices. You can find a power outlet at many campsites, restaurants, coffee shops, and sometimes large supermarkets or department stores. The drawback is that you’re always looking for a place to charge. When you find a power outlet, you’ll have to stop for an hour or two to charge everything up. If you’re riding in a rural area, you might not see a power outlet for days. You’ll have to pass through a city or town in order to power up.
Another Option: Rim dynamos (bottle dynamo)
Rim dynamos produce power using the same technology as dynamo hubs. The difference is that the dynamo unit mounts to a fork arm instead of being built into a hub. The rim dynamo is a small cylinder that sits against the rim. When your wheel spins, it causes the rim dynamo to spin and produce power.
These were common on vintage bikes before dynamo hubs were introduced. Rim dynamos of the past rubbed against the tire instead of the rim. They were commonly were used to power a small headlight. Early models were noisy and made the bike ride kind of funny.
Rim dynamo technology has improved greatly over the past few years. Modern models offer a number of benefits over dynamo hubs and are worth considering for some riders.
Rim Dynamo Pros
- You can move the dynamo away from the rim so it doesn’t cause any additional drag when not in use.
- You don’t need to rebuild your wheel to install or repair a rim dynamo. They simply clamp to the fork. This makes rim dynamos easier to install.
- Rim dynamos weigh less than hub dynamos.
- Rim dynamos can produce more power than hub dynamos.
- You can easily remove a rim dynamo when you don’t need it.
- Rim dynamos are more efficient than hub dynamos.
Rim Dynamo Cons
- When your rims are wet or while traveling at high speeds, the rim dynamo can slip against the surface of the rim. This causes a reduction in power output.
- Rim dynamos cause more resistance than hub dynamos.
- Rm dynamos are louder than hub dynamos. They can make an annoying whirring sound.
- There are fewer light and USB charger options that are compatible with rim dynamos.
- You must position the rim dynamo so it sits against the rim at the correct angle and pressure. They can be a bit finicky.
- They require a bit more maintenance. You must replace the o-ring occasionally.
- Rim hubs don’t work well when the rim is contaminated with mud, snow, or other debris.
Final Thoughts About Dynamo Hubs
Whether or not a dynamo hub is worth it depends on the type of riding you do and how fast you ride. Dynamo hubs offer a reliable and efficient way power your bike lights and to keep your devices charged. If you ride for a few hours per day while touring, you can keep your phone, GPS, camera, eReader, and extra battery charged and keep lights running. You don’t have to worry about running out of power.
Of course, there is a cost. You are sacrificing some pedaling power and speed because dynamo hubs create additional drag. There is a small weight penalty as well. For these reasons, you will ride a bit less efficiently when using a dynamo hub. There is also some added complexity and cost. For bicycle tourists, bikepackers, and commuters, the pros usually outweigh the cons. To me, the convenience is worth the slight reduction in efficiency.
What do you think? Are dynamo hubs worth it? Share your tips and experience and tips in the comments below!
Sunday 2nd of April 2023
I just want to know is there a dynamo with a battery that it charges so your lights don’t go out when you stop at traffic lights
Monday 10th of April 2023
Some dynamo hub lights have a capacitor inside that charges up as you ride. When you stop at a traffic light, the light will stay on for up to around 5 minutes before it goes out. Not all lights have this feature. Look for 'standlights' when you buy a dynamo hub light.