Son Dynamo SON 28 Hub
The SON 28 is the dynamo hub that made hub generators worth having: made by Schmidt Maschinenbau in Tuebingen, Germany, it puts out its full 6 volts and 3 watts from about 16 km/h on a 700c wheel, loses only about 1.2% of your effort at 25 km/h, weighs about 430 grams and runs on sealed bearings covered by a five-year warranty. It is the dynamo we build for touring bikes, commuters and bikepackers who want a bright light at walking pace and enough power to charge a phone or GPS on the road. This page covers the Son Dynamo SON 28 Hub.
The SON 28 is sold here only inside a wheel we build. Choose the rim, spokes and nipples in the configurator and the finished wheel ships from Georgia laced, tensioned and trued by hand.
Design and construction
A dynamo hub is a generator: magnets in the hub shell spin around a fixed coil on the axle and produce alternating current that a light or a charger turns into something useful. Schmidt's trick is efficiency; the SON 28 reaches full output at lower speed than any competitor and drags less when the light is off, which is why a SON wheel feels like a normal wheel. The hub is sealed so that air moves in and out only through a pressure-compensation system rather than through the bearings, which is why the bearings last for decades and why the five-year warranty covers them.
The SON 28 comes in rim-brake, 6-bolt disc and centerlock disc versions in 100mm spacing, in 32 and 36 hole, polished silver or black, and there is a 150mm fat-bike version. Output is through a spade connector, and Schmidt recommends 4.8mm piggy-back connectors if you run a light and a charger together.
This is the front hub, and a front hub has no freehub. What matters here is the part of the hub that carries the wheel: the bearings, the seals, the axle and the two flanges, and the front 28 dynamo shares all of them with its rear partner. It is the simpler half of the pair and the one that runs longest between services. The driver and engagement story belongs on the rear hub's page; this page is about a front wheel that spins freely, stays sealed and builds stiff.
How it rides
A SON 28 wheel rides like a wheel. The drag with the light off is small enough that most riders cannot feel it, and with the light on it is about the cost of a slight headwind. What you get in exchange is a headlight that is bright at 8 km/h on a climb, a rear light that never needs charging and, with a charger such as the Sinewave or Forumslader, a USB port that keeps a phone or GPS alive for a week in the wild.
For faster riding and smaller wheels the SON Delux reaches full output at higher speed with less drag; for touring, commuting and charging, the SON 28 is the dynamo we recommend.
On the road or the trail the front hub's job is to disappear: spin freely, keep water out, and hold the flanges still so the wheel tracks where you point it. The front 28 dynamo does that with the same bearings and seals as the rear and none of the rear's complexity, and because a front wheel carries less load and no torque it stays true longer than the rear on the same rim. When the rear finally needs a look, the front usually does not.
Specifications
| Position | Front |
|---|---|
| Axle options | QR 5x100mm Front |
| Drillings | 32h, 36h |
| Spoke head | J-bend |
| Brake | rim-brake |
| Left flange diameter | 54 mm |
| Right flange diameter | 54 mm |
| Left center-to-flange | 31 mm |
| Right center-to-flange | 31 mm |
| Spoke hole diameter | 2.6 mm |
| Weight | 440g |
| Material | Aluminum |
| Finishes | black, blue, green, orange, polished, red, silver |
This version
This version is the front rim-brake hub in QR 5x100mm, drilled for 32h, 36h, about 440g, in black, blue, green, orange, polished, red, silver. Those are the only things that differ between the versions of the 28 dynamo; the shell, bearings and seals are the same.
This is the rim-brake 28 dynamo, with no rotor mount at all: a lighter, simpler shell for road, track and classic frames that stop on the rim. It builds into the lightest wheel the model can make and it is the version to choose for a rim-brake bike; the disc versions of the same hub have their own listings.
Sizes, fit and compatibility
The Son Dynamo SON 28 Hub comes in the drillings listed on this page in 100mm spacing with the brake mount shown in the configurator: rim brake, 6-bolt or centerlock. J-bend spokes in any gauge; we build most dynamo wheels with DT Champion or Competition or Sapim Race spokes and brass nipples.
It pairs naturally with the Velocity Dyad, Atlas and Cliffhanger, Mavic A319, HED Belgium, H Plus Son TB14 and Archetype and the touring rims in the catalog. Pick touring, commuter or bikepacking as your bike type in the configurator and it recommends a spoke count and lacing pattern.
Build it into a wheel
This hub is live in our Custom Wheel Program for road rim brake, track and road single-speed and touring builds. Start a build with the SON 28 Hub and the configurator opens with this exact hub pinned at the top of the Son Dynamo list — you choose the rest of the parts and it validates every combination as you go.
How Son Dynamo tests its hubs
SON (Wilfried Schmidt Maschinenbau) states that “Each hub dynamo and headlight is thoroughly tested during and after assembly” in Tübingen, Germany, where a team of about 30 designs, develops and produces on CNC machinery; roughly 15,000 hub dynamos are sold annually. All SON hub dynamos are rated 6 volts / 3 watts conforming to German road-traffic regulations (StVZO). Published SON 28 data: mark of conformity K 834 for 16-inch to 29-inch wheels; efficiency 65% at 15 km/h in a 28-inch wheel; no-load loss 0.5 W at 15 km/h; 26-pole neodymium rotor; hollow 10 mm stainless steel axle; 6082-T6 aluminum shell; SKF 629-2RSH bearings; 440 g (disc 6-bolt 460 g, center lock 430 g). The SONdelux is approved under K 687 for 16-inch to 28-inch wheels (400-716 mm) with the Edelux headlight; it and the straight-pull SON 29 S weigh 390 g.
SON states that “Best possible protection against water ingress is realized by the unique pressure compensation system”, warns that grease on the skewer shaft can block it, and says the hub must never be exposed to strong water jets or immersed. The generator works without gears or contact. Bearings are “high-end bearings sealed on both sides from SKF”; SON's FAQ says they are lifetime-lubricated, normally run maintenance-free for many tens of thousands of kilometers, need no adjustment, and are replaced by the manufacturer should a fault occur.
From Son Dynamo
Certifications
- StVZO mark of conformity K 834 (SON 28) — 6 V / 3 W per StVZO, approved for 16-inch to 29-inch wheels; efficiency 65% at 15 km/h in a 28-inch wheel (SON technical data as reproduced by retailer bike-components) (source)
- StVZO mark of conformity K 687 (SONdelux with Edelux) — Licensed for wheels 16-inch to 28-inch (400-716 mm) in combination with the Edelux headlight; SON instructions Sept 2016 (source)
- Made in Germany — “made in Tübingen”; “Bike Lighting made in Germany”; design, development, production and sales in Tübingen (source)
- 5-year guarantee — All hub dynamos, manufacturer's faults during standard use; excludes incorrect installation, improper use, natural wear, accidents (source)
Sources on Son Dynamo's site:
- Hub dynamos - SON Hub Dynamos
- For Standard Forks - SON Hub Dynamos
- For Thru Axles - SON Hub Dynamos
- FAQs - SON Hub Dynamos
- Repairs & Guarantee - SON Hub Dynamos
The figures, certificates and media above are Son Dynamo's own. ProWheelBuilder does not run these tests; our part is the wheel we build on the hub.
Building it at ProWheelBuilder
Schmidt makes the SON 28 in Tuebingen, Germany; ProWheelBuilder is an independent custom wheel builder in Georgia and not the manufacturer, and Schmidt's five-year warranty rides with the hub. Spokes are cut from the ERD we measure on the actual rim, the wheel comes up in stages on a tensiometer, and it is stress-relieved and trued before it goes in the box; tape and a valve go on if you ask.
The configurator filters to what fits, crosses out what is not made, and prices the build as you go.
Warranty
Son Dynamo's warranty. SON dynamo hubs carry a five-year warranty against defects in material and manufacture.
ProWheelBuilder. Our one-year wheel warranty applies to any wheel we build around this part, alongside whatever the manufacturer offers. Inside that year, broken spokes are replaced no matter how they broke, and the wheel labor is ours - truing, re-tensioning or a full rebuild. A rim or hub failure that the maker covers, we claim for you and see through; one the maker declines, we answer with an eligible replacement at 25% off current retail. Shipping both ways is yours, and components you supply yourself fall outside this cover.
Full terms are on our Policies & Warranty page.
SON 28 Hub questions
Can I use this hub with disc brakes?
No - this is the rim-brake version and it has no rotor mount at all, which is exactly why it is lighter and simpler. It is the one for a rim-brake road, track or classic frame. A disc frame needs one of the disc versions of this hub, which are listed separately.
SON 28 or SON Delux?
SON 28 for touring, commuting and charging, where full output at low speed matters; Delux for faster riding and smaller wheels, where it is lighter and drags less.
How much drag does a SON 28 add?
About 1.2% of your effort at 25 km/h with the light on, and much less with it off. Most riders cannot feel it.
Can I charge a phone from a SON 28?
Yes, with a USB charger such as a Sinewave Reactor or Forumslader; the SON 28 has the output to run a light and a charger together at touring speeds.
What is the SON warranty?
Five years, including the bearings, which is unusual and possible because the hub is sealed against air exchange through the bearings.
Is ProWheelBuilder the manufacturer of the Son Dynamo SON 28 Hub?
No. Son Dynamo makes the hub. ProWheelBuilder is an independent custom wheel builder in Georgia that builds it into a finished wheel to your spec.
Which axle spacing does it fit?
QR 5x100mm Front. Measure between the inside faces of your dropouts if you are unsure, or text us.
Not sure? Text or leave a voicemail on 470-253-0929 or email info@prowheelbuilder.com — you will be talking to the people who build the wheels.
