Son Dynamo SON 28 6 Bolt ISO Disc 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 6 Bolt ISO Disc Hub.
The SON 28 comes from us only as a finished wheel: pick the rim, spokes and nipples, and we lace, tension and true it by hand in Georgia before it ships.
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.
A front hub is a bearing carrier with flanges, and that is the whole job of the front 28 dynamo: two sealed bearings on a stiff axle, end caps for your fork's standard, and flanges spaced to give the spokes a good bracing angle on the rotor side. There is nothing to engage and nothing to swap. Everything written about freehubs and engagement applies to the rear hub only; what you get up front is the same shell quality and the same seals without any of the moving parts.
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, Thru Axle 12x100mm Front, Thru Axle 15x100mm Front, Thru Axle 15x110mm Boost Front, Thru Axle 12x110mm Boost Front |
| Drillings | 24h, 28h, 32h, 36h |
| Spoke head | J-bend |
| Brake | 6-bolt disc |
| Left flange diameter | 59 mm |
| Spoke hole diameter | 2.6 mm |
| Weight | 410g |
| Material | Aluminum |
| Finishes | black, blue, green, orange, polished, red, silver |
About this listing
What sets this listing apart from the other 28 dynamo versions: 6-bolt rotor mount, QR 5x100mm, Thru Axle 12x100mm, Thru Axle 15x100mm, Thru Axle 15x110mm Boost and more, 24h, 28h, 32h, 36h drilling, about 410g, in black, blue, green, orange, polished, red, silver. Pick the one that matches your frame and rotor and the rest of the hub is identical.
Six-bolt is the original disc mount and still the most universal: any ISO 6-bolt rotor from any brand bolts straight on, rotors are cheap and easy to find anywhere, and the six-bolt flange is a robust, simple interface that has been on mountain bikes for twenty-five years. Centerlock rotors do not fit it.
Sizes, fit and compatibility
The Son Dynamo SON 28 6 Bolt ISO Disc 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 with us
We build this hub to order. Open the Custom Wheel Program with the SON 28 6 Bolt ISO Disc Hub already selected and pick the parts around it; it is offered for gravel and road disc, track and road single-speed, touring, mountain bike, MTB single-speed and fat bike builds, and the configurator will not let you assemble a combination we would not build.
Testing, standards and warranty at Son Dynamo
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 a 5-year guarantee on all hub dynamos covering manufacturer's faults during standard use; incorrect installation, improper use, natural wear, and accidents are excluded. SON repairs or replaces the product.
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
Everything in this section is published by Son Dynamo. ProWheelBuilder is the wheel builder, not the tester, and the hub reaches us as the maker ships it.
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. We measure the rim before we cut a spoke, bring the wheel up in three or four rounds with a gauge, stress-relieve it between rounds and true it last, then tape it and fit a valve if you want it tubeless.
Only compatible hubs and spokes appear in the configurator, impossible combinations are struck through rather than hidden, and the price is live.
Warranty
Son Dynamo's warranty. SON dynamo hubs carry a five-year warranty against defects in material and manufacture.
ProWheelBuilder. Built into a wheel by us, this part is covered by our own one-year wheel warranty on top of the maker's. For a year we replace broken spokes whatever caused them, and we cover the labor on the wheel - truing, re-tensioning, a rebuild if it needs one. If a rim or hub fails and its maker covers it, we run that claim for you; if the maker says no, you get an eligible replacement rim or hub at 25% off retail. You pay the shipping each way. Wheels built from parts you send us are excluded.
Full terms are on our Policies & Warranty page.
SON 28 6 Bolt ISO Disc Hub questions
Will my rotors fit this hub?
This is the 6-bolt version: any ISO 6-bolt rotor bolts straight on with six T25 bolts, which is still the most common and the easiest rotor to replace anywhere. Centerlock rotors do not fit it - for those, take the centerlock version of the same hub, 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.
Which axle spacing does it fit?
QR 5x100mm Front or Thru Axle 12x100mm Front or Thru Axle 15x100mm Front or Thru Axle 15x110mm Boost Front or Thru Axle 12x110mm Boost Front. Measure between the inside faces of your dropouts if you are unsure, or text us.
Does it need special spokes?
No. It takes standard J-bend spokes, which the configurator offers in every gauge and finish we stock.
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.
