B&M IQ Cyo generator light/ Shimano DH-3N70/71/72 Generator Hub

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mander's picture
B&M IQ Cyo generator light/ Shimano DH-3N70/71/72 Generator Hub


Last winter, I got tired of not being able to see in the dark. In late September, I got caught by the darkness on a distance ride to Ben Lomond. I had to go 20 km with only the fog line visible in my shitty Planet Bike 2*AA Beamer 5 beam to guide me. This was fun, but a bit mickey mouse---I was glad that the pavement I was travelling on was fresh and there were no serious road debris or other hazards to worry about, or it would have been pretty tough going. As well, I moved into a new place that required me to commute every day through an unlit park with fast, twisty roads. When I hit a curb going around a roundabout in this park, that did it for me. I was going to get a good light, dammit.

I did a fair amount of research into different high-powered lighting systems, and concluded that if you want anything that works you are going to have to spend around $300. I settled on the idea of a generator hub and light. I was attracted to the idea of never having to worry about a charge, as high powered batteries tend to drain fast (3-6 hours depending on how powerful your light is) and I am bad at keeping on top of stuff like that. Also, generator lights look hell of rando, and at the time, rando was the new tarck.

After lots of shopping, I got a B&M IQ Cyo with a Shimano model DH-3N71 Ultegra-branded generator hub (the 70, 71 and 72 all seem to be pretty much identical). This combination seemed to offer high performance at a price point well below the next level up (the ultra-blingy Schmidt SON with a Schmidt Edelux light). I've now used this setup through a winter of commuting and several summer distance rides, and it's definitely fulfilled my initial expectations.

The DH-3n71

Shimano's generator hub is terrific, especially since i got it for £40. I got the 32 hole model and built it into an MA-2 rim I also got cheaply (£10!). The total cost of the wheel was around USD $140 after double butted spokes, but other tarckists might not be so lucky.

At 680 grams it's very heavy compared to a regular front hub---the normal Ultegra front hub only weighs around 150 grams. However, for many riders the added 500 mL bottle of pop you will be carrying everywhere won't mean much when you balance it against the convenience of never having to worry about a battery charge.

I thought that drag was going to be an issue, but it hasn't bothered me at all in real-world conditions. Just turning the hub axle you will feel substantial resistance. But the hub smooths itself out at speed, as the resistance is a product of magnets alternately pushing and pulling on the axle, and the push and pull approximately equal each other. An internet tester said that the added resistance with the light on is on the order of having to climb an extra 4-6 feet over the course of a mile. I can't feel any added drag at all when the light is off. There can be noticeable "buzz" or vibration when the light is on, especially when your bearings are a little loose. This has given me some concern when riding around my back alley with the light on in bright sunlight, but it's never bugged me on long rides in the dark.

The hub has good old, user serviceable ball bearings on the non-drive side, with Shimano's excellent borazon races as seen on all their high-end hubs. However, on the driveside where the generator is, the bearings cannot be accessed. I heard it's set up like this because a hub generator is very complicated, and Shimano's engineers don't trust you not to fuck it up. I'm not sure what's on that side as Shimano seems to be pretty cagey about it, but I assume it's some kind of cartridge bearing. If they can't be serviced at all, then the clock is definitely ticking for this hub. Hopefully when the time comes, there will be some way to replace those bearings rather than throw the $80-100 hub away. To be fair, the Schmidt SON's bearings are also not user serviceable; they require that you send it away to a designated service place every 50 000 km or so. But as there does not appear to be a similar service program obviously available for Shimano's hubs, this is definitely something to consider.

You attach the light to the hub via a little male plug in the hub shell just outside the right hand hub bearing locknut. The hub comes with a female plug that you put on the end of your light's wire. You can then unplug the hub when you want to remove the front wheel. This setup works fine and doesn't require soldering to install.

The IQ Cyo

The B&M IQ Cyo is excellent. It cost me £70, but I haven't regretted the purchase at all.

The Cyo has a robust plastic body with a metal top that I think is there to act as a heat sink for the single LED. The big advantage that the LED offers over halogen systems like the Schmidt E6 is long life. People with halogen systems have to carry a spare bulb, just in case, but this is not a worry with LEDs. As a tradeoff, there are riders who prefer a halogen's yellow beam to the blue beam of an LED.

The LED's light is focused and directed by some fancy, engineered reflectors that give you a clearly defined aisle of light to ride in. The reflectors also concentrate the light's power at the top of the beam, where there is more road to be lit up. A light without this feature will light the road right in front of you brilliantly, because it is almost directly facing the beam; but it will leave the road 100" away a lot more dim, because it is not facing the beam anywhere near as directly. These optics are primarily what the high price gets you... there are a lot of cheaper lights that are nominally more powerful, but still don't light up the road as well because they are sending so much of their light up into the night sky, 2" in front of your wheel, and other places where it isn't needed.

The sides of the aisle are a little on the narrow side, so when you're going around very tight corners as in a roundabout, you sometimes won't have light where you'd like it. This is a tradeoff for more riding light in most situations.

The light comes with a fork crown mount but I put it on a scavenged bottle generator mount, halfway up a fork leg. This is working great so far and it's allowed me to use a front rack.

Paired with the Shimano hub, the Cyo is nice and bright at just about every speed. It theoretically gets a little dimmer at very low speeds but since you're going slow, this has never mattered to me in the field. When it's on I can descend at 60-65 km/h in the dark with confidence, but not much faster. It is extremely bright and gets noticed -- it lights up stop signs for blocks, and I can see it reflected off the pale faces of the drivers my bike is pointed at. There is a little capacitor that keeps it on for a minute or so when you're stopped. This is useful to keep car drivers from forgetting about you at intersections.

The Cyo's switch can get clogged with dirt on a muddy, rainy ride, which then dries out and stiffens up the switch's action. To get it clean again, I flush it out with water while working it back and forth. This doesn't appear to impede conductivity or anything, but it's unfortunate all the same. I think it's made much worse by my mounting the light on a fork blade; if it were up on the fork crown tucked behind the fender, it would probably stay a lot cleaner.

Security is an issue with a light like this. It's kind of expensive to leave bolted to your bike, although I don't think it's the kind of thing that casual thieves would be too interested in, unlike e.g. battery lights that attach with a QR. I have a secure lockup area for my regular commute, but I might not want to lock up in the same place every day without something like that. You could certainly fill the allen heads with rubber cement or the like if you were worried, or even try adapting a Pitlock-type system to work. The light itself is held onto the mount with only a single nut, so you could also jury rig a QR system with a wing nut.

Summing up

For the money, these are excellent products and I recommend them to tarck.

Fri, 08/07/2009 - 17:49
steveaustin (not verified)

here are models without switches for use with a bottle generator that you physically disconnect when you aren't running it, models with switches, and models that automatically turn of during daylight. I opted for the manual switch, because I find the dynamo drag is so small that I often leave it on for extra safety during the day.

Sun, 07/25/2010 - 23:24
hambeki's picture

The bots are getting pretty good.

MoonCat wrote:
All bikes are really just overpriced crosschecks with different geometries.

Mon, 07/26/2010 - 16:28
bexley's picture

Thanks, bot. Brought this to my attention.

Nice review, mander. If I hadn't already spent too much money on my bike, I'd definitely go with this combo for its cost and relative effectiveness. I don't need the better performance, if it is better, but the SON20R's 390 grams to the Shimano's 680 is at least one objective reason for me. And why go with the Edelux if I don't need it? I think it looks badass and it's not as fragile as the E6.

Can't wait to be battery free.

Tue, 07/27/2010 - 09:19
mander's picture

p.s. I now know exactly how to service the bearings on shimano dynohubs, have detailed pics, will poast if there is interest.

p.p.s. no one has stolen the cyo off my bike yet, apparently thieves dont really give a shit

Tue, 07/27/2010 - 23:18
Patch's picture

going with the same setup as bexley. just got to.

Thu, 07/29/2010 - 07:08

I've run an IQ Cyo for several months now on the Gunnar and I liked it enough that I got another for a second bike.

Thu, 07/29/2010 - 23:29
klondikebear's picture

Do want front rack/dynamohubiqco for next bike

What are the chances these prices will go down 50% in the next year and a half?

Fri, 07/30/2010 - 11:19


Fri, 07/30/2010 - 19:03
mander's picture

Hey klondike, VO guy has hinted on his blog that the Next Big Thing in dynamo hubs may be coming out soon. i think he used the words "game changing" but also suggested that it's going to be comparatively cheap.

Fri, 07/30/2010 - 19:08

mander wrote:
Hey klondike, VO guy has hinted on his blog that the Next Big Thing in dynamo hubs may be coming out soon. i think he used the words "game changing" but also suggested that it's going to be comparatively cheap.

He said that early this year and said it would be coming out late next year, for what it's worth. There will always be something "better" and cheaper next year so you should always wait for it!

Tue, 08/10/2010 - 09:24
klondikebear's picture

VO Blog wrote:
I recently mentioned a new dynamo hub design that I thought was revolutionary and might make existing high end dyno hubs obsolete. We have a production-ready sample that we'll be testing over the next few weeks. But I can already tell you that the build quality looks very impressive and, if my calculations are correct, it will cut overall rolling resistance by more than 50% compared to any other (production) dyno hub that I'm aware of, while maintaining the same 3w/6v output. If all goes well we should have them in around 3 months. The cost will be considerably lower than existing high-end dyno hubs. We do want to be clear that this is not technology developed by VO (we're not that smart), but from a small company we ran into almost by accident. I'm sure that you have questions about them, but those are all the specs we'll reveal for now; sorry.
06 july, 2010


Tue, 08/10/2010 - 10:33
wsfwang (not verified)

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Fri, 08/27/2010 - 21:46
klondikebear's picture

mander, care to share an update review on these? especially the hubs. I have you used them through the winter and did everything hold up nicely, and what maintenance did you do during the winter if you did use them.

Sun, 09/18/2011 - 17:32
mander's picture

Still going strong, two winters/ 20 000 all-weather kms later and about to go through a third. The Ultegra bearings are terminator strong and this will help offset the complete lack of maintenance that most users will put them through. You can take them apart on both sides; here are the unofficial instructions (nb Shimano does not want you to attempt this). As far as I know though, cones are near-impossible to get so you're limited to changing the grease and bb's.


I have serviced my bearings once, fucked up the axle threads on one side putting them back together though. This is easy to do because of the "stepped" design of the axle---the locknuts go right on the edge of the "step". You need to make sure that the locknut on each side has plenty of thread before torquing on it; and after that, it's a good idea go easy on the torque. To make things slightly tougher, getting preload right on a dynamo hub is a bit finicky, because even with the bearings set perfectly it rolls very rumbly; the normal smoothness test doesn't apply in the same way. Especially on your first try, you might wind up fiddling with it more than you would with a regular front hub; and this tends to stress the threads. Anyways, my stripped axle threads were too bad but not a big deal in the end. The cone on that side is now held on with JB Weld; and my situation on that side of the hub is now merely like that of a normal user who's too scared to open it up. I will probably open mine up again before winter to give them one last check/ servicing on the side that is still accessible.

As with a lot of shimano hubs they ship with the bearing preload set super tight so even if you don't plan o doing any servicing it's worth your while to back them off a little before running the hub.

My Cyo no longer turns off; when the switch is in the off position it now merely disables the standlight. Weird huh? I don't really care since I would be leaving the light on most of the time anyways. It's annoying about three times per year when i am hammering across country in a fast group in excellent daylight and feel like i could really use those extra few watts. I could always unplug the light in those cases, but I guess it just isn't that annoying.

These dynamos are still a super choice imo. will most likely get a SON for my next dynamo but the shimanos are so much cheaper and so high quality that I'm tempted to just get another one.

Sat, 10/01/2011 - 18:35
mander's picture
(Reply to #15)

ps: lol@ VO's end product/ hind sighted lol@me for getting excited about it.

Sat, 10/01/2011 - 18:33
JUGE FREDD's picture

The actual generator guts are better than the SONdelux and competitive with the SON28 -- it's just the switching gimmick that pointlessly doubles the weight in the first gen version that VO ordered from http://www.sp-dynamo.com/

They've got models going into production that are SONdelux size/weight and put out more power, I know one of VO's competitors is testing them now.

Supernova is getting both designs produced for them, available in Europe in a month (QBP should pick them up by spring)

It's a struggle, but you cut out his tongue, and his last words are "atmo atmo Atmo ATMO ATMOOOOOGORIHGGHRSHGGRLMGGMMGMgrrglegurglegrr....."
– akasnowmaaan

Tue, 10/11/2011 - 20:13
JUGE FREDD's picture


It's a struggle, but you cut out his tongue, and his last words are "atmo atmo Atmo ATMO ATMOOOOOGORIHGGHRSHGGRLMGGMMGMgrrglegurglegrr....."
– akasnowmaaan

Tue, 10/11/2011 - 20:13
Rusty Piton
Rusty Piton's picture


emor wrote:
Bicycle commuting is the worst way to get anywhere except for all the other ways.

Thu, 10/20/2011 - 15:38
JUGE FREDD's picture

That's one of the proto hubshells they've made but I doubt anybody's going to order a run of them for retail — probably intended for OEM on folders with a narrow axle.

This is the mainstream design:

Supernova will be selling it with centerlock and a shimano-style light connector at a healthy markup: http://www.supernova-lights.com/en/products/infinity_s.html

It's a struggle, but you cut out his tongue, and his last words are "atmo atmo Atmo ATMO ATMOOOOOGORIHGGHRSHGGRLMGGMMGMgrrglegurglegrr....."
– akasnowmaaan

Sat, 10/22/2011 - 22:56
sean's picture

I got the aluminum axle version... Pretty worried about stripping it after reading this thread.

As for lighting systems... Dynamo is the way to go. I got the cheapo B & M halogen Lyt N Plus because I prefer the natural color light. Plenty bright when it's dark. Doesn't do a whole lot if you're under streetlights except help drivers see you.

Toplight Flat S or whatever in the rear. It's red. It's cheap. Hasn't broken yet.

Tue, 01/08/2013 - 19:06