What are the hub model numbers?
Their first gen hubs were pretty weak. At one time Peter White cycles had some comparison tests of the models available then. The early Shimano (NX30) had far more drag when 'off' due to a bad stator design. Not worth buying or trying to use.
I have 3 of the second gen (3d71) which work quite well. I initially built up wheels in 700 race, 700 wide and 26" mtb figuring I would just put them on what ever bike I was going to ride that night. But they stayed put on 2 of my touring bikes, Trek 520 (700c wide) and my Gary Fisher (mtb). With no electric load the drag is not even noticable when riding. The electric drag load is generally proportional to the power being requested. They were designed to output a max of 3 watts at normal riding speed. Not a huge amount. You can't be running high power headlights with them. 3 watts is the max target. None of those 20 or 30 or 60 watt lights. I took one on my cross USA ride and kept the headlight on at all times during the day when on roadways. I have a Sinewave Converter (regulated 5 volt usb charger port) that I used to power the mp3 player when on trails. Basic saftey rules, no earbuds when on the roads, lights always on when on the roads. I had a friend tell me he could see my headlight from a couple miles away during day time. I could slightly feel the drag. My guess was I was giving up about 1/2 mph which would add about 10 minutes to a full day's ride. Some rough numbers, humans output about 100 watts to ride at an easy speed. Pro racers are in the 500 watt range at race speed. By comparison a 3 watt hub generator is pretty minor. It takes a lot more effort to push knobby mountain bike tires. Far less drag than those awful bottle generators that have 50 watts of mechanical drag to produce 3 watts of electricty.
There are generator specific head lights. IMO, the Shimano is quite poor. The main issue is it has a secondary LED in the lens that runs up and over the light which messes up your night vision. I have the Planet bike LED headlights on the bikes now. They have a capacitor in them so they stay lit when you stop moving for a bit. The LEDs put out a lot more light per watt. And they don't burn out if you go down a hill to fast. Don't waste your time with incandescent bulbs or Krypton gas bulbs. Peter White carries some very nice generator specific lights like the E3
We did get an early SON for my wife for her midnight century rides and ultra races. The version with the black tube body that was more prone to water infiltration. It's quite expensive but was the best overall. Built up in 650c and since sold off as she when back to 700c bikes. There are many other brands now.
Could be the bearings need a repack. The 3d71 hubs have shimano's high end bearings. Some of other brands have sealed cartridge bearings. Those can be over tightened depending on the axle design. It's quite easy to destroy a Shimano hub (rip the wires out) if you allow the connector to turn on the axle when adjusting the bearings. That hub looks to be in new condition so it's probably to factory spec.
