More adventure riders & gravel racers are looking to dynamo hubs for endless light & charging electronics, and now the field serviceable Kasai Dynacoil adds in the peace of mind of being able to troubleshoot common issues on the side of the road. Being able to charge a GPS and power LED lighting greatly extends the range of bikepacking and ultra-distance racing adventures.

Kasai Dynacoil FS field serviceable dynamo hub generator

Kasai Dynacoil FS field serviceable dynamo hub generator

c. Merry Sales

Some riders are reluctant to make the leap to dynamos because of real or perceived threat of system failure that could leave them powerless and far from home. I’ve begun using dynamo powered lighting for shorter adventure rides, and I don’t really want to ever go back to worry about charging or replacing batteries. My personal trips are seldom far from civilization, but many bikepackers are riding further afield and putting their gear through brutal tests in harsh conditions. For them especially, the idea of the user-serviceable Kasai FS Dynacoil Hub sounds great.

Kasai Field Serviceable – Tech details

Kasai Dynacoil FS field serviceable dynamo hub generator

Most all dynamo hubs are factory sealed, meaning all of the generator internals are inaccessible, so not even a bike shop could service it if you have a problem. That’s a big issue if you have a failure out on your travels – as the hub likely will need to be shipped back to the manufacturer for service. Plus, since the dynamo is laced into your front wheel, it also means that any serious dynamo hub problem will mean rebuilding your wheel, too.

Kasai Dynacoil FS field serviceable dynamo hub generator

The Kasai FS (or Field Serviceable) concept is to make it easier to deal with a dynamo over the life of the hub and wheel. Bearings can be easily replaced, and the electricity-generating dynamo can be threaded out of the hubshell itself, so you can replace the magnetic coils if needed – all with simple standard tools thanks to big wrench flats on the hub. No need to ever teardown and rebuild the wheel on account of the dynamo, just service the parts that need maintenance over the life of your adventure setup.

Kasai Dynacoil FS field serviceable dynamo hub generator

Kasai distributor Merry Sales says the most common failure mode for a dynamo is water infiltration. With a 36mm wrench, you could conceivably pop it open to dry it out after one too many river crossings saps your electricity-producing capability.

Kasai Dynacoil FS field serviceable dynamo hub generator

The Kasai Dynacoil FS hubs feature a 6061 alloy hub shell available in 32 or 36 hole drilling & black or silver anodizing, and 7075 alloy endcaps. The teflon-insulated copper coils wires are made in Japan, and the hubs meet Germany’s strict StVZO road lighting standard. Kasai says the hub is 72% efficient from 10mph/16kph, putting out 3W of power at 6v for 26″-700c wheels. Claimed hub weights range from 445-495g depending on axle & brake configurations.

Kasai FS dynamo hub – Options, affordable pricing & availability

Kasai Dynacoil FS field serviceable dynamo hub generator

The Kasai FS is relatively affordable stacked up to other dynamo hubs and is available in several configurations. A rim brake, quick release hub sells for $130, or for 6-bolt disc with a QR axle for $140. Thru-axle Kasai FS dynamo hubs are a bit more expensive – $190 for either 6-bolt or centerlock disc – but unfortunately it seems to only be available in a 15mm x 100mm axle configuration. That will fit a number of adventure bikes, but a large number of recent gravel bikes have adopted the increasingly more common 12x100mm axle standard.

Kasai Dynacoil FS field serviceable dynamo hub generator

A replacement coil assembly sells separately from $90, and standard sized sealed bearings are used.

The Kasai dynamo hubs are available now, in the US from a number of direct sales outlets like Soma Fabrications, and are distributed to independent bike shops by Merry Sales.

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Dolan Halbrook
Dolan Halbrook
2 years ago

I’ve heard of Shimano and SP dynohubs failing, but never with Schmidt SONs. Still, not a bad idea.

shreded7
2 years ago

Affordable. Not bad. Sometimes, I think stuff is easier to service needs to be serviced more often. I have also never had issues with two Shutter Precisions or a Shimano dynamo, but I have met people who have. All that said, being able to replace the bearings is a cool move.

Jclaa
Jclaa
2 years ago

Such great progress in the dynamo world. About freaking time!

Matthias
Matthias
2 years ago

Good idea. It bears mentioning though that “Germany’s strict StVZO road lighting standard” is mostly a law to put limits on dynamo power output, put illogical limits on combinations of lighting equipment and generally pretend bike lighting was stuck in the the era of incandescent bulbs.
Germany is usually rightly renowned for good standards of durability and efficiency; the StVZO isn’t one of them.

typevertigo
typevertigo
2 years ago

Indeed, about time this happened. Am practically sold on the concept of dynamo hubs, but the lack of DIY bearing servicing has held me back.

Just a slight bummer that 12 mm through-axles aren’t supported yet, but that should be an easy addition later on.

Maybe this is a dumb question, but would it be theoretically possible to run the hub without its dynamo guts? Perhaps temporarily convert it into a “get-me-home” unpowered front hub configuration?

Joe Maki
Joe Maki
2 years ago

Couldn’t the 12mm axle problem be solved by a simple 15mm outside diameter, 12mm inside diameter tube?

Hurricane
2 years ago
Reply to  Joe Maki

It could….the only problem I see is the axle/ fork interface between 15mm and 12mm.

Dinger
Dinger
2 years ago
Reply to  Hurricane

I did this with a 100x15mm wheel to use on my gravel bike. I did have to have the axle caps turned down to 19mm O.D. to get it to work with my fork.

lihtanlihtan
2 years ago

If you go to the Merry Sales website, you’ll see that that Kasai makes a 15mm to 12mm through axle converter ($19.99), as well as a 110mm boost conversion kit ($24.95) for their dyno hubs.

JOHN A
JOHN A
2 years ago

It looks like Iron Man’s arc reactor – cool!

KlaMue
KlaMue
2 years ago

Interesting approach! But who would take a heavy “coil assambly unit” together with a heavy 36mm spanner on a bike packing trip? Seams better to me to solve the “water infiltration” problem.

bast1aan
2 years ago

This is a great development.
However one note. Besides efficiency of 72% it is also of much interest how much mechanical power (drag) the dynamo consumes if no electricity is consumed. I think it is even more important than efficiency, because when I don’t use the dynamo I don’t want the extra drag of it. SON hubs and modern Shimano perform well on this factor, but several mostly older hubs and also a few modern hubs can perform terrible on this, dragging even more mechanical power with lights off than lights on, especially at higher speeds.

Oleg Volkov
Oleg Volkov
1 year ago
Reply to  bast1aan

If You have dynohub You shouldn’t switch OFF You Light at all. Not to see but to be seen. I do so. Ride with 5 SP hubs since 2012, it’s OK.

Dominic
Dominic
2 years ago

I like the lack of dish, and the price. Also curious like the above poster about how draggy it is.