Shimano Dynamo Hubs

Val Kleitz from Seattle Bicycle Supply sent us some great info about the Shimano Dynamo Hubs.

shimano dynamo hubs

Here’s their report:

Shimano Dynamo Hubs:
Practical Considerations

When we realized that we would be carrying the NuVinci CVT hubs at Seattle Bike Supply, we decided that we should offer a complementary front wheel. Since the best application of the NuVinci will be as a practical, solid commuting wheel, we tried to build up the most practical front commuting wheel to go with it. Here in the Pacific Northwest, we may not have much seriously cold weather to deal with, but the commuting conditions are otherwise fairly extreme in the winter. Rain, mud, and darkness are the rule rather than the exception. To cope with this, we chose one of Shimano’s Dynamo front hubs.

Building a generator into the hub is not a new idea, even for Shimano. Many riders still remember the Sturmey Archer Dyno hubs that were made as early as 1936. As with any electric device, though, modern advances have improved these hubs drastically, so that today’s generator hubs are much more powerful than the early ones, though functionally identical. As the hub turns, a strong magnet built into the hub shell rotates around the core of the generator, producing current. There no more moving parts than a normal front hub, and the current produced becomes useful for lighting at around 3mph with a 700c wheel. It is a sign of the extreme practicality and increasing popularity of these hubs that there are at least five major companies offering them now.

Shimano makes several models of Dynamo front hub, and we chose among them based on the conditions we expected them to endure. The DH3D30 hub is compatible with standard 6 bolt disc brakes, has 36 holes and a quick release axle. Disc brakes are extremely practical in wet conditions, offering consistent braking and lower maintenance than rim brakes, and 36 hole wheels will withstand much more abuse and need less truing than 32 or 28 hole versions, while weighing only slightly more.

Once the hub is in a wheel, and the wheel on a bike, a light must me connected. Shimano makes one, which has both a white LED and a halogen bulb, and throws a well focused beam. In this area, though, there are many choices, and here, also, modern advances are worth pursuing. There are many new generator powered LED headlights that give superior illumination, and many of them also have the ability to remain on when the bike is stopped.

For the NuVinci test bike, I used a very basic halogen headlight left over from another generator set. It is a well designed light from Union, and while there are better lights available, I found that this one provided much more than adequate light for dark bicycle trails. As with most lights of this type, its beam was not very noticeable when riding directly under street lights, but is definitely strong enough to catch the attention of drivers and to take over when the street lights are gone. The light I used also had no “standlight? function, as many modern lights do. This function charges a capacitor while you ride, which then keeps the lights going for up to two minutes at a stop. I have ridden both with and without this function, and I find that, while I like it, it is not essential. If I am stopped, I am usually well out of the way of the traffic, and also usually directly under a street light. Otherwise, I am moving, and lit.

Riding with a Dynamo hub can be very liberating. There is no friction between the tire and a drive wheel, as with frame mounted generators, and the resistance is almost impossible to notice when riding. I do have friends with Dynamo hubs who claim that they can tell whether their light is turned on or not based on feeling the added resistance, but even they admit that they may be imagining it (I think that they check under their mattresses for peas before going to bed, too). There is no need to wonder how much life is left in your battery, and no need to remember to plug anything in at the end of the ride. You can ride indefinitely without any dimming of the light, and you should not need to think about removing it from the bike when locked up outside the corner store, since the generator is the front hub, and the lights should be firmly bolted to the bike. All you have to do is ride, and know that you have light. The lighting system becomes an integral part of the bike, a standard feature, rather than something else to add on and worry about. A good light system based on a Dynamo front hub offers simplicity, reliability, and safety – exactly what every commuter needs.

Val Kleitz


  1. Jim

    thats a sweet looking hub, I wish I had seen this last week as I just purchased a new set of laced wheels for my commuter bike in Sac…
    I think I’ll replace the hub on my wife’s bike with one tho, as she loves her headlights at night!!

  2. Bill

    Indeed, a great recycled and improved idea, and the main reason I invested in the dynamo-equipped Specialized Globe 3.1 instead of a comparably priced and equipped Cannnondale commuter. The problem: Shimano apparently cannot provide replacement parts. After a mild crash totaled the dynamo-driven headlight (with the dynamo off-on switch)my bike dealer, the reliable Gotham Bikes of Manhattan, ordered a replacement light from Shimano via Specialized. More than two months later, Speccialized says the part still remains unavailable. Meanwhile, the dynamo keeps spinning along…but I wish I had bought the Cannondale instead. Caveat emptor.

  3. Val

    Bill: You should be able to install any number of other lights on that dynamo. The Shimano switch is nifty, but not strictly necessary. The switch includes a regulator, which keeps the high voltage from fast speeds from burning out your lights, but many of the lights available today already have the regulator built in. The basic Union light in the pictures does, and any light that you find from Busch & Muller will also have overvoltage protection built in. Don’t give up on the Dynamo – find a shop that knows about lights, and hook it back up. Also, if you like the Shimano lights, any shop that orders from Seattle Bike Supply can order one right now – we have them in stock. It’s not really so crucial at this time of the year, but getting lit is never bad.

  4. ktronik



    I have found a way to get up to 12.8w from the shimano / SON dynamo hub, using a series cap before the refictior, into 3 series LEDs…

    I have different curves that I use for on or off road use…

    the fastest curve gives 1150ma into 3 series LEDs @40km/hr…but I mainly use a flatter curve…peak 910ma @ 27.5 km/hr into 3 series LEDs…

    I have built a few lights using cree xr-e & SSCp4 LEDs…so my lights, powered from the shimano dynamo maxes out @ 720lm+!! giving HID bright lights from a dynamo…


    its a really simple circuit to get it going, with extra mods for extra functions if needed…it can be customised for any type of riding / speed…

    normally the hub, wants to give 500ma @ all speed by changing the voltage…

    by holding the voltage low (series cap), the current rises

    using a 100uf Bi-polar cap in series before the bridge ref I get:

    7km/hr=8.47v @ 50ma
    15km/hr=9.44v @ 250ma
    23km/hr=10.24 @ 610mq
    27.5km/hr=10.62 @ 910ma
    37km/hr=10.14 @ 630ma

    using a 200uf bi-polar cap in series before the bridge ref I get: (same speeds as above)

    100ma, 480ma, 18km/hr peak @ 660ma, then 600ma @ 24km/hr, I use this curve for off road racing & the 100uf curve for on road commute…

    I bigger the cap the more boost down low & the less peak power…

    you can mix 2 different curves together, or even mix in a voltage doubler for up to 75ma @ 4km/hr, 100ma @ 5km/hr & 200ma @ 7km/hr…

    so a lot can be done just by using a series cap before the bridge ref…

    he dynamo hub could be used for powering equipment in the day…maybe use a LM7805 to give USB power…GPS, MP3, phone charging, ect

    you also could use the circuit to charge battery’s & run your stuff off that, that way when you stopped your GPS wouldn’t turn off… & yes you would have a little switch box on your bar to select the different riding curves / low speed boost or battery charging…

    all this can work… & its all very easy to do…

    I been testing this circuit with both shimano & SON hubs, for about 2 years… not one problem…now that the new breed of LEDs are out, it makes sence to dynamo it up!! my dynamo light is now as bright as a HID (on paper)

    BTW the cree LED is a better bet rather than the SSC p4… it has less colour shift when over driven & less colour shift over time…the seoul is also a more floody type of beam…

    I use the SSC P4 of off-road racing using the 200uf curve (peak 660ma)& the cree on-road with the 100uf curve (peak 910ma)…

    I have full data for DIYers if needed… just drop me a email…



  5. Pingback: Get up to 12.8w from the shimano / SON dynamo hub at Bike Commuters

  6. Davey

    Hi there! I live in the UK and I’ve just won a Brompton folding bike on eBay. (it still needs collecting) These bikes have 16″ (349mm) 28 spoke wheels which are not so good for people outside the lightweight category. I would like to get some 36 hole rims but where can they be found?

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