alo

A number of people here use dynamo hubs. Some may wonder, how much do they slow you down?

Riveting

What slows me down the most is having my rechargeable headlight die while it's dark out, and then trying to navigate the steep and twisty downhill MUP's here in southern Denver. I had my lights die on me years ago, not fun, that's why my commuter now has a dynamo.

pdlamb

I have two bikes with dyno lights. The first one I used the on-off switch religiously, until I was surprised to get over the ridge leaving town and found out I'd left it on. I never noticed the difference. Now I just leave it on. The second has a light sensor/switch, and I let the light do the switching.

How much difference in speed? Pretty close to zero, certainly negligible in my riding.

veganbikes

I don't really notice. I know it makes a slight difference but honestly I don't care too much. The lighting they create is quite helpful!

Tourist in MSN

Touring, my dynohub is almost exclusively used to create USB power. Around home, since I have a dynohub I might as well use it so I bought the lights for it too. Initially only had the front light, but added taillights several years later. Usually leave the lights on around home, but when touring and charging batteries, the dyno powered lights are off..

I know there is drag, I looked at the data before I bought my first dynohub in 2013. But,I can not feel any extra drag from the hub, I suspect that the speed difference is not much different than changing tire pressure by 1 or 2 psi.

Racing Dan

Its a good video, but it does lack a more comprehensive comparison to batteries. You can carry a lot of batteries and still come out ahead, if dynamo drag is in the 3-15w range. For instance, it takes less than 3W to ascend an additional 1 kilogram on a 10% slope at 10 km/h (!). - not to mention the price of good dynamos and the plug5 charger. Yikes! :-)

adamrice 

To decide whether a dyno hub makes sense requires you to take into account a lot of variables. Perhaps just knowing that you won't need to worry about recharging is enough to decide the matter. Or the abstract appeal of being completely off the grid. But if you're going strictly by the numbers, you need to look at how often you'd need to recharge a battery, how long it will take to recharge, whether you'll have opportunities to recharge when needed, the relative losses of extra weight vs hub drag (if that matters to you). Etc.

Over on bicycles.stackexchange.com, there's a discussion on the subject of dyno hubs specifically for bikepacking races, and even within that narrow context, it was pointed out that Mike Hall sometimes used dyno hubs and sometimes did not.

unterhausen

7 minutes of 100k, I think I can live with that. Maybe if I was racing night crits I would worry about it

polyphrast

Since there is basically no new design in dyno hubs, numbers from 2013 are still valid.... with load (3W lighting), all SON/SP/Shimano hubs have at most 8W at 30 km/h // 20 mph (with SON being the best) Without load, the better ones from Shimano and all hubs from SON and SP have below 2 W @30 km/h without load. There is plenty of measurement data in the german magazin fahrradzukunft.de (if there is interest, i pick the articles for you)
So a dry chain, loose fitting clothes or your general position on the bike has a much higher influence with respect to watt losses...