Is the drag from a Dynohub noticeable?

The wheels on my touring bike are wearing out and about to need replacement. I'd been considering adding a dyno light system to this bike for a while, so now seems like the time to do it. However since most of the miles on this bike are daylight miles, I don't want to add much full time drag for the sake of lighting. My question is, how noticeable is the drag from a dyno system when the lights are off? For a bike that is primarily ridden during the day but occasionally ridden on very dark roads/trails, am I better off with a good battery light system or a dyno system?

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Permalink Reply by Apie (11) on August 6, 2012 at 5:44am

New SON dynamo's have no drag at all, I've seen them and spun the wheel myself.  I was debating  getting one, but I think a simple headlight will save me $400

Permalink Reply by Doug Haynes on August 6, 2012 at 5:55am

As noted the SON hub has pretty much no drag but that is reflected in the price.

They all have drag, I find Simano and Sram to be about the same, but it is hardly noticeable when spinning a built up wheel. 

There are a couple here at the shop, come check them out.

Permalink Reply by terryg on August 6, 2012 at 6:06am

I've been using dynos on the majority of my bikes for a few years now, including my LHT (every day).  I just leave it on all the time, I notice nothing.  I use the Shimano every day and various SON on my other bikes.  I've noticed that as the more recent Shimano offerings have improved, their price has increased.

I'll add that I built an inexpensive around-town wheel for a friend last Christmas, around the Sanyo hub (see Peter White, for info) and a Sun CR-18 rim.  No trouble at all, and she leaves it on 24/7.  That's a rather impressive hub for the money.  In fact, a friend of hers was so impressed I got to build another one.

btw, I leave mine on whenever I'm on the bike.  I think it comes from a motorcyclist past life.  Anyway, it seems like a no-brainer to me to have reliable and effortless lights on a bike.  I'm happy to answer questions.

Permalink Reply by Tony Adams on August 6, 2012 at 7:33am

I'm still somewhat traumatized by the extra difficulty of fixing a flat on my three speed's rear tire, so I wonder, does the dyne hub's cabling make it more difficult to remove the wheel to fix a flat in the field?

(I know that if the offending object is still visible that it isn't always necessary to remove a wheel to fix a flat.)

Permalink Reply by Nançois on August 6, 2012 at 7:37am

I think one of the perks of having a dyno-light is that you can leave it on all the time, for whatever miniscule increase in visibility that might provide. I hooked up an inexpensive Planet Bike Blaze (I think it's a 1-watt LED) to an older Sturmey-Archer dynohub and just love it!

Permalink Reply by Doug Haynes on August 6, 2012 at 7:46am

It is easy to disconnect the wires, I have never had an issue with it.

Tony Adams said:

I'm still somewhat traumatized by the extra difficulty of fixing a flat on my three speed's rear tire, so I wonder, does the dyne hub's cabling make it more difficult to remove the wheel to fix a flat in the field?

(I know that if the offending object is still visible that it isn't always necessary to remove a wheel to fix a flat.)

Permalink Reply by terryg on August 6, 2012 at 8:00am

Agreed, my experiences as well.  

Shimano hubs I'm familiar with have a very convenient little bit that clamps the leads from your headlight to the hub.  SON hubs connect soldered (to the light's leads) paddles to tabs on the hub.  The Sanyo hub mentioned previously is probably the most fiddly, using a little block that holds the leads in a socket on the hub.  In all cases the leads can/should be permanently mounted to the bike (cable ties to fork leg, & the like).  Ditto the lights.

notoriousDUG said:

It is easy to disconnect the wires, I have never had an issue with it.


Permalink Reply by Far'arned Retrogrumpalunkus #63 on August 6, 2012 at 8:01am

The only time you will notice it is when you are spinning the wheel by hand in the bike (or spinning the axle in the hub and it will feel "notchy" due to the magnets snapping to each pole of the winding.  You won't notice that when it is running.  

A dyno slows the wheel down a very little bit and you might feel a slight vibration.   But you won't feel it when pedaling.   I really can't feel the difference between a dyno hub and a non-dyno hub on or off.   Every once in a while I can feel a slight hum of a vibration at some lower speeds when it is on-but rarely.  Almost never.    What I do notice is that I have light whenever I want it.  No worry about batteries, nothing -just flick the switch and I've got a bright light for a long as I want to pedal.

Get a an LED light that puts out some decent light -measured in Lux.  30 or more lux is what you want.  The more the better but that is going to cost you.  Also get a light that has a standlight -this means it will stay on (not as bright, of course) when you come to a stop and are waiting at an intersection.   You need a light for when you are stopped so stupid cagers don't run you over.

I have 2 bikes with dyno hubs on them.  I've got a Sturmey X-FDD with built-in drum brake in the front of my city bike.  The drum bake is OK. It could be a bit stronger or my tastes but it never has any issues with wetness so that is a big plus. The dyno has never given me a touch of a problem.  They make a slightly larger version with a bigger brake.  But it's a bit more weight too.  Still, a really nice front brake and dyno combination for not too much money.

the other Dyno I have is an SRAM i-Light.   It's been pretty good although I didn't like SRAM's lack of documentation on their hubs.  You have to measure the dimensions yourself because they won't give it to you.  not a big deal but it sort of pissed me off to have to measure a brand new hub like it was some junk-pile take-off castaway instead of having that information available like Sturmey did.  Sturmey is 1000% classier of a company than SRAM IMHO.  This particular hub is made for disc brakes but you don't have to run disc brakes on it.  The only downside of having the disc brake lugs on it is that the flanges are not symetrical so you need to have two different lengths of spokes and the wheel is a tiny bit less strong because of the dishing of the wheel to account for the room for the disc brake that you are not using.  Not a big deal.  The wheel will still be much stronger than a typical rear wheel with a cassette or freewheel stack as they are even more asymmetrical.  The hub is a good deal for $66 bucks though. The Son or Shimano hubs will cost you way more and the electrical dynamo insides are the same as used on many shimano dynohubs --made by Panasonic I think.  

As for as plugging it in, it's a snap.  If you can plug in a toaster you can plug in the connector on a dyno hub.   Most of them just plug in or unplug with a tiny little connector on the drive-side of the bike right near the axle.  Just don't forget it before you go to pull the wheel.  You might pull the wires out of the connector or damage it.  The hub side of the plug is usually pretty robust so even if you do this you can just buy a $2 plastic replacement connector if you broke it.  

Permalink Reply by Craig S. on August 6, 2012 at 8:43am

This is a great question and thanks to all who answered and shared their info and experience as I've had the same question and more about dynos.

Permalink Reply by Doug Haynes on August 6, 2012 at 10:37am

I am here till eight tonight, tomorrow and Wednesday.

Cameron Puetz said:

I'll try to find some time this week. Are you working any evenings in the near term?

notoriousDUG said:

As noted the SON hub has pretty much no drag but that is reflected in the price.

They all have drag, I find Simano and Sram to be about the same, but it is hardly noticeable when spinning a built up wheel. 

There are a couple here at the shop, come check them out.

Permalink Reply by Leah Jone on August 6, 2012 at 11:34am

I have a Shimano DH-3N80 dynohub that was built up at Uptown bikes last summer for my LHT and am madly in love with it. Always having my lights with me makes choosing to ride my bike so much easier.

It is easy enough to disconnect the wires when you need to change a flat on the front tire, so that wouldn't be a reason to skip out on one in my books.

Permalink Reply by ilter on August 6, 2012 at 1:22pm

I too am happy w/ my dynohub. If you don`t mind the wheel`s shadow, Sheldon Brown`s method makes it easy to detach the wheel as the headlight comes with it:

http://sheldonbrown.com/org//raleigh-competition/pages/10-headlight...

Some hubs can be rotated either way, some only one way. So with Sheldon`s way, you may or may not place the headlight on the left side.

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