How Much Do Dynamo Hubs Really Slow You Down?

I TRULY appreciate your research and effort in this video, but there is a question I have. From strictly the Shimano offerings, you picked the most powerful (and draggiest) and the one of the worst offerings in the 3D32. My question is, not a video, but if you want to that would be awesome, could you compare just Shimano dynamos for the average guy who doesn’t have $350+ to spend on a SON? We ALL KNOW SON dynamos are the best, I just would love to see a comparison on how the the Shimano offerings stack up against each other. Especially the S501, and if you had to rank all of Shimano dynamos, how would you rank them from top to bottom?

Thanks a lot for sharing your precious experiences.

As usual, these stupid bastards totally ignore The Best >> Sturmey Archer XL-FDD dyno with DRUM brake that lasts 35,000 miles easily. And the hidden brake side sealed bearing might last that as well.
My first one has 32,000 miles with an Edelux front light and Toplight XS Plus tail light. Now is on it's third frame. Still looks and works as good as new. 4 bearings got crunched into the magnets at 17,000 miles. Had NO effect. LOL. Unlike Sh it mano hubs, mine needs ZERO service. AND it doesn't need taking the spokes apart to change bearings. LOL. What a design farce that is.
My lights are always ON. My tour bike is 120 lbs loaded, 74 when doing century+ rides around home. It has done 45- 46 mph several times with my SA XL-RD5w. Rohloff14 tops out at 43.
My Nexus 7i with roller brake boat anchor could only do 38.1. So obviously, the dyno has near zero actual effect.

Awesome. I opted for the B&M IQ X and Son hub :D Holy moly. this is a detailed report. Thank you!

Thanks. Super.

Interesting results. Thanks.

My back of the envelop analysis would go like this. A 2.4A USB port uses 12W of power and you'd add ~5W for the inefficiency of the dynamo to get a 5-17W reduction in power. Your light cyclist produces 120W and will have 103-115W remain to move the bike. That is 86-96% of the power available without the dynamo. Your heavy cyclist produces 180W and will have 163-175W remain to move the bike. That is 91-97% of the power available without the dynamo. How much of the power loss translates to speed loss is, as you say, depending on many factors. The results that you saw is within the expected theoretical values above.

For lights, high efficient LED lights are around 85-100 lumen per W. How much power that you lose will depend on how bright the lights are.

Better quality dynamo would reduce the 5W power loss but would not do any thing for the loss from the USB or light.

Sucks to be a smaller rider who also a female. I consistently produce like 50watts while weight around 70kg bikepacking with the same bike and luggage as heavier rider no wonder I struggle all the time 😅

10 watts lost is 20% power lost for me 😢

how many dynamo output V

Do dynamo's slow you down? NO
What they do is increase the drag/resistance so you have to input more power to move at the same speed.
SPEED is the number one thing that everyone moans about.
You're riding a pedal cycle for enjoyment or transport, You're not in the TDF or any other RACE!
Take your time and enjoy the ride.
I ride an ICE Qnt recumbent trike which weighs well over 30lbs fully loaded with panniers, dynamo hub, lights, water bottle, cycle comp etc and I average 11-17 mph on a ride depending on terrain.
The thing is at 59yrs old I can ride all day long and do over 100 miles without pain.
I also have a set of battery lights just in case but they run off the battery pack that gets charged by the Dynamo this also charges my phone/satnav and is through charge compatible, this will run the lights all night if needed.

P.S.
You will get more power at slower speeds from a hub dynamo when used with smaller wheels 20" 406 instead of 27/28" 700c as the wheel rotates faster for any given speed, unless you use one made for smaller wheels like the 'son' 16-20" (less magnets & less drag).

Fantastic info! Love the geeking out on this material. 👍

Then there’s me, who just likes to coast and not peddle down hills so the dynamo actually doesn’t do anything. It’s not like the dynamo requires constant torque to work.

I wish there was a good bicycle shop in my town

Would like to see the comparison with the pedal cell dynamo included.
Thanks for the video.

I think more reliant you are on light the more a dynamo hub helps.

i use 21700 li-ion fenix batt 🙂

Excellent reviews and comments. I have a Shimano hub as standard on a Towny 7D - can I swap out the installed lights for something brighter?

Great video, thanks a lot! I do think though that you overestimate the w/kg output of the average bikepacker. This number will vary massively across cyclists of course, but I do think that 2 w/kg average for bikepacking is quite a big overestimation. To comfortably pedal that for 5+ hours, the cyclists threshold should be 3.5 - 4 w/kg, which is higher than that of most bikepackers (pointy end of ultradistance racers excluded) - closer to the range of competitive cyclists.
I'd be with you in the uphill case - 2w/kg are produced when going uphill a 5% slope. But on the flat road, your results could be a bit misleading.
That being said, your content is fantastic and I really appreciate the effort in sharing your knowledge! Cheers from Germany.

Nice number crunching. Sadly the chargers are all well outside my budget. Thankfully you can get a half decent dynamo lighting setup for city commuting at reasonable prices.

If dynamos produce energy because of the rotation of the wheel, theorically bikes with smaller wheels (20", 16") would get more power out of one, right? I'd like someone to explain me.

Amazing video , it will be great if you can add a link to the tools you are using it will be great

Can you only harness the energy generated during the ride? I would much rather the store energy generated into a battery and then have that charge my stuff.

The other problem is they just are not bright enough. My rechargeable headlight puts out 1600 Lumens at the highest setting. But my light has five settings, Low, Medium, high - 1600 Lumens and two different speeds of flashing. Yes, I have to keep it charged, but I also carry two batteries.

Good video 👍

This is stupid, having a whole USB hum integrated.
It wasted money and adds more points where the system can break.
All you need is a little wire run from your wheel to your lamp.

just buy a SON and stopy worrying. Unless you're just interested in comparing numbers :) Interesting though.

Honestly, there is no choice. If you want a light bright enough to cycle safely in the cold of a winter morning to work a hub dynamo is the only choice. Batteries die in the cold and the hassle of managing a removable light is just annoying. With a dynamo hub the light is always there and when you need it.

There are so many other things that slow down more like studded tires, snow, traffic,... It does not matter.

Well, this is obvious: dynamo will add at least as much drag as the plugged in device draws. The tricky part is how much more parasitic drag is created with different dynamos and electrical loads.

How do I buy your type of flat bar

I'm really thinking of splurging for a SON28 and cinq 5 combo.

If I'm providing my own buffer battery, should I expect any performance difference between the Pure and Plus variants?

Takeaway: Just use top quality battery lights.

This was a great review and also accommodated for the 90kg riders which is a great amount of data reviews.

Thanks

thanks for this video!

There are dynamos and accessories to charge your devices/phone through USB. Nice! I have not seen that before, I somewhat feel old just learning about this now.

Idk how I have missed this channel. Great video and certainly gives me food for thought. I am just thinking of using it to charge my battery banks. Seems more dependable than using my solar wing and hoping for good weather. Thanks for the well researched info. Ride safe!

Thanks for the reviews and information, today things cost so much and there are so many choices, not always easy to try them all.

I really want to make this dynamo hub set up on my mountain bike, however, my front wheel use disc brake rotor. Is it possible to set up dynamo hub in my disc brake wheel? Hoping for your answer. Ride safe!

Hi , I have a problem with the xt dynamo, the wheel rolls slowly. How can I send you the video?

SO a hub dynamo adjusts itself based on energy draw? That's mind boggling that it can do that.

Damned, I am a small rider with 90kg and there is no useful result for me in this simulation.

Quality looking hubs those Son’s,Shimano know a thing or two about dynamo hubs too at almost half the price,think SP do a hub that has changeable axle options from Qr to boost etc 🤔

Would it make sense to have a hybrid dynamo/battery system and charge the battery in the downhills? How about engaging the dynamo automatically when braking? The descent of a big mountain pass is easy to spot and the dynamo can be turned on manually, but what about automatic detection of downhills? It could be optimized so that you could get the lights at night but the drag is minimized.

I wonder if you could do some kind of set up where the dynamo kicks in on max power when going downhill, or braking, to blast-charge a Li battery or capacitor of some sort - that way it won’t slow you down at all as it will be effectively mopping up power you’re otherwise wasting in braking? A bit complex I know but a proper project for us bike-geeks!

A bigger rider is less affected by drag? Whachu talking about Willis? Only if they are the same height as the smaller rider. I'm" 6'7"/2m01 and drag affects me a lot. I use a SonDeluxe Widebody and to me the drag is barely perceptible. Way less than a headwind.

Also you assume the bigger rider and the smaller rider's bikes weigh the same. That's an erroneous assumption also, my bikes are big and they are heavier.

I don't even think you should assume the gear would weigh the same for bigger and smaller riders. My clothes are bigger than a smaller rider's clothes and thusly weigh more.

anyway.....carry on....

are there hybrid style dyanmoes that charge a battery when going down a hill with excess energy produced and then use that stored energy on the flats or a climb to save on your time lost per hour?

I love Dynamo lights. That said, I had a Son hub crack and now steer clear of them. The crack started at the inside corner of the tessellated joint between the two halves of the hub. Sharp internal corners are stress risers, and I think it's just a flawed design.

Can you turn the dynamo off (disengage) at will like it were an electro mechanical dynamo?
What do you think of solar panel (warmer places) on carrier to provide for charging phones and even bike lights at very little weight penalty?