Shimano's 3N20 hub dynamo is perfectly adequate for most service; it has served on hundreds of thousands, possibly millions, of commuter bikes. All that you get extra on the much more expensive 3N80 hub dynamo is Ultegra-level seals. If you don't use disc brakes, you quite needlessly pay extra for that as well on the 3N80. Forget about rebuilding the hub dynamo, or even servicing it. Its service life is 40K kilometres and then you just chuck it. I've never actually seen the service kit advertised but I imagine it will be about the same price as a new dynamo hub costs at the discounters.
A SON hub dynamo might last three times as long but costs substantially more than three times as much.
The Shimano 3N20 has more off-service drag than a SON, but with modern lamps you'll leave the lamps on all the time anyway, and when it is on and driving the lamp, the 3N20 has *less* drag than it has off service!
The Shimano 3N80 for a third or less of the price of a SON, only has more drag to obsessives splitting hairs.
I have both the SON and variants of the best Shimano on similar bikes, and an AXA sidewall generator too for that matter, fitted by Gazelle in a crazy weight weenie moment to save a few grammes off a luxurious vacation bike with every other possible trimming imaginable (a fruit and nut episode!).
A SON gives you great bragging rights, but I took the one I have because it was a standard fitment already included in the price of the bike, a "delete option"; were I given the choice, I would have chosen the Shimano hub dynamo because I'd had good experience of it.
Most of my riding at night in town, which is the most critical nighttime riding I do, is under 15kph, from speed bump to speed bump, and in those conditions the Shimano comes up to current faster than the SON. It's marginal (see what I said about hairsplitters, and the capacitors in the most modern LED lights are pretty good at filling in the lucanae), but this is about my life, not bragging rights.
There is just no rational basis at all for seeing the Shimano as inferior to the SON. The knee-jerk reflex preference for the SON in the elite cycling community is another example of cycling "efficiency" running wild and producing zero greater speed or comfort at several times the cost of the rational choice. It's snobbery, pure and simple.
Except if you're a genuine world tourer, or you commute 10k miles every year, the SON is the choice of a fashion victim, and very likely a waste of money. Even the Shimano 3N80 needs its claim on your money closely evaluated while the 3N20 is available for €19 (as reported further up this thread)!
A tip: German Ebay (ebay.de) makes it easy to buy these dynamo hubs built into rims, usually good-quality computer-built surplus wheels from manufacturers. Always make sure you get the fitting kit if one is required. The reason for looking at built wheels is that the cost with the better Shimano dynamo hubs is generally not very far above the cost of a built wheel with the cheaper hub, so you may as well have the best Shimano, necessary or not.
Andre Jute
