28-inch front wheels with hub dynamos and disc mounts are usually expensive and still rare. This is why many bike manufacturers do not use the low-maintenance power supplier. If you want to retrofit, you have to go looking for it yourself. We have checked the range on offer for you and show you what you should look out for when retrofitting.
Regardless of whether it's a budget or mid-range model, the large quantities come from the Sanyo or Shimano factories. SRAM does not produce its own dynamos, but has them manufactured by Sanyo. Shimano dominates this market segment with various models costing between €35 and €85. These hub dynamos work reliably, but they are relatively large and have a large flange distance. The large flange spacing makes the wheel more stable.
If you are prepared to dig deeper into your pockets, you get less rolling resistance, a more compact design and lower weight. Two manufacturers have made the best name for themselves here: Shutter Precision (SP) from Taiwan and Schmidt Maschinenbau from Tübingen. SP also produces the Infinity S for Supernova, which is distinguished by better seals, eight anodised colours and a Shimano-licensed centre lock mount. It costs around 189 euros.
The SON (Schmidt's original hub dynamo) has been in production since 1995. There are now a large number of models in all possible variants. The most common SON 28 and SONdelux cost around 199 to 249 euros, depending on the model. Good service and constant innovations such as the pressure equalisation system have led to SON's excellent reputation, while DT Swiss and Sapim are the leading manufacturers of spokes. Good wheels use double-thickness spokes, usually 2/1.8/2 mm, instead of continuous 2 mm spokes, which are robust yet light. Touring and cargo bikes often use extra-thick spokes, while sporty bikes often use aerodynamic bladed spokes. A wheel with 36 spokes is heavier but also stiffer than one with 32 spokes. It is important that the spokes are tensioned correctly and evenly.
There are many rim manufacturers; DT Swiss and Mavic both have a good reputation. Rim wear is not important for disc brakes. Stiffness, weight and width are important here. A heavy rim is much more noticeable when riding than a heavy hub. The rim width (see drawing below) is decisive for which tyres can be fitted. Most trekking bikes have rims that are around 25 mm wide and have a rim width of around 19 mm. This means that they can accommodate tyres from 28 to 62 mm wide. While a few rims, such as the DT Swiss TK540, are almost identical in the rim brake and disc versions (except for the turned flanks), disc rims generally have thinner flanks and are therefore not suitable for rim brakes.
Of the six bikes we tested, three (B.O.C., Bike-Components, Bike-X-Perts) are fully configured. Schmidt Maschinenbau offers many variants, the bike shown is an example. Komponentix and Whizz Wheels offer customised wheels.
Conclusion: The following also applies to disc wheels with hub dynamos: There is no such thing as the perfect wheel. A compromise is always necessary. Decide whether price, weight, stiffness or the quality of the hub dynamo is important to you!
You can download the full-length article from issue 5/2014 as a PDF.
