Thursday, August 4, 2011

Bad Vibrations

Shimano Alfine Hub
Riding my Rivendell last weekend, I was going downhill when I became aware of a strong vibration in my hands from the handlebars. At first I thought I was imagining it: This felt like "shimmy" and I know this bike does not have shimmy; this has never happened before. Was the headset loose? At the bottom of the hill I stopped to check, but everything seemed fine. Then I noticed that my lights were on. I must have forgotten to turn them off from the previous night. And then it hit me: Could this be the dreaded high-speed dynamo hub vibration? Jan Heine mentioned it in a recent Bicycle Quarterly article, and Somervillain reported it after building up his latest bike. In both cases, Shimano hubs were involved. The hub on my bike is a Shimano Alfine.

I turned off the light and began to cycle again, picking up speed. No more vibrations. Turned the light back on and picked up speed once more. Again the handlebars began to vibrate. Yikes. The only way I can explain not having noticed this earlier, is that I must have never gone this fast with the lights on before - which makes sense, because I normally only turn them on when it's dark and I cycle slower  in the dark. This time I accidentally left them on in the daytime, and when I first noticed the vibration I was going about 25mph. But once I began to pay closer attention, I could feel it starting at 17mph or so.

Schmidt SON Dynamo Hub
The following day I rode the same route on the Randonneur and intentionally turned the lights on. This bicycle is equipped with a Schmidt SON Delux hub. I did not feel handlebar vibration at high speeds. Reading up on this issue some more, the vibration effect has been reported for many different hubs, including Schmidt - though not the SON Delux model specifically, as far as I can see. Is the SON Delux immune to this?

I am frustrated to experience the vibration on my own bike with the Shimano Alfine. At the time I was choosing a dynamo hub for this bicycle, the considerably more expensive Schmidt seemed frivolous, and everyone assured me that in practical use (as opposed to efficiency tests) the new Shimano models worked just as well. However, my recent experience appears to contradict this. It is disappointing to learn that I am limited to cycling at speeds below 17mph if I want to have the lights on without my handlebars vibrating.

Some have suggested that it is not the dynamo hub itself that's responsible for the vibration effect, but that it is a complex interaction between the hub, wheel size, and frame. That could very well be, and if so it will take forever to uncover the pattern of causality. What have been your experiences with dynamo hubs and vibration at high speeds?

51 comments:

  1. This is most probably due to the design of the dynamo, the magnetic fields being made and broken may at speed may create harmonics that you can feel.

    An unfortunate design.

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  2. MelissatheRagamuffinAugust 4, 2011 at 7:17 AM

    Is your light attached to your hub?

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  3. from a technical point of view is quite expectable, but it should not happen with a manufacturer like Shimano;
    let's not forget that the target usage for dynamo hubs are city bike which are usually going with less than 17mph (approx 30kmph);
    considering the good quality of rechargeable batteries and high energy density they provide combined with the efficiency of LEDs now i'm using only this type of lighting systems;
    dynamo hubs should remain only for heavy city bikes;
    btw: what is the weight of your bike; i suspect a similar situation with ABS systems on cars if it is reasonably light;

    have a nice ride :)

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  4. I have the same hub as somervillian (or if not, just a model number off) and I have never experienced the vibration. I have it mounted on a 700C wheel with 32mm Schwalbes on a slightly-too-small 63cm frame, and it was also built by Anthony at Longleaf.

    I often leave my lights on for my entire 40 mile roundtrip commute, and although there are not many hills, I occasionally go faster than 25mph.

    Maybe i just need to ride this bike faster more often to test it out! I'll kick it up a notch on the way home and let you know! :)

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  5. Is the SON Delux the only dynamo hub immune to this then?

    Not sure, but the SON Delux is designed for 20" wheels, requiring higher RPMs to generate the same output as the SON made for standard road-sized wheels. RPM for RPM, it puts out less than the regular SON. This may account for why the SON delux does not vibrate as much. But this is just speculation on my part.

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  6. I've noticed that with the Schmidt SON hub. I didn't know I could get rid of it by turning the lights off -- thanks. It's never bothered me that much.

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  7. These are very honest questions, don't take them wrong.
    So what if you have a vibration? It is not permanent and you are not always cycling at these speeds and this is not your only bicycle, right? What is the deal with some vibration? Does it hurt you somewhere (you nerve issues) or are you just being particulary fiddly?
    I guess I am used to making do with less than perfect bikes so I don't really see the deal...

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  8. MelissatheRagamuffin - Not sure what exactly you mean? The hub is the source of energy for the lighting and the headlight & tail light are wired to it.

    Montrealize - Yes, nerve damage issues. But even for a "normal" person it is not good to experience such vibrations in the hands for long periods of time as it can cause nerve damage. My tolerance for a bike's issues has to do with how I use it. On a transportation bicycle I would not be riding very fast or far, so it does not pose a problem. But these bikes are designed precisely to travel long distances - hundreds of miles at a time, and hen needed, in the dark. One cannot cycle hundreds of miles while experiencing such vibrations in the hands without damaging the nerves there. It is a serious flaw for people considering this set-up for night time touring and the like.

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  9. I've had vibration on my Schmidt ever since I first owned it. Only happens when it's on and it's subtle enough that the only times when I notice it is when I'm at low-medium speed (ie ~12 mph) on very smooth pavement. In some cases, in the daytime, it's the only hint that I have that I've left my lights running. I know that you've got hand/nerve issues, V, so do you find it particularly bothersome or just odd?

    Anecdotal (and I've let my BQ subscription lapse so haven't read Jan's most recent writeup), but I've found from time to time, that the vibration maybe less noticeable if I tighten the axle nuts on the hub. Of course, whether that's a real remedy or something incorrectly inferred simply because I've become acclimated to the vibration is yet to be determined.

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  10. What is the deal with some vibration? Does it hurt you somewhere (you nerve issues) or are you just being particulary fiddly?
    I guess I am used to making do with less than perfect bikes so I don't really see the deal...


    The problem I have with my Shimano hub and the vibration I experience with the lights on is that after an hour or so of sustained vibration in the handlebars (which happens if I'm riding at >13-15mph, which isn't even that fast), my hands begin to go numb. This doesn't happen when the lights are off.

    I remember reading the review of this hub in Bicycle Quarterly (Vol.9, no.2 if anyone is interested) where Jan Heine mentions the issue, but I dismissed it as an issue that only a very experienced and nuanced cyclists would detect, and that I probably wouldn't even notice. Not so.. my first ride with the lights on and it was immediately felt.

    The fact that some Shimano hub users don't experience the vibration may have to do with how well their bicycles dampen the vibration. I'll venture a guess that the fork design may have a lot to do with how well the vibrations are isolated.

    Jan Heine also mentions that some Shimano hub owners report the hub bearings being too tight right out of the box, but doesn't mention a connection between this and the experience of vibration. i.e., it may not be related. I haven't checked the cone adjustment on my hub, but I suppose it's something worth checking.

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  11. So this is not a defect which is under a warranty?

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  12. Ah ha, so THAT's what it is. The Pelican has a Shimano hub and sure enough, this vibration happens at higher speeds. I hadn't read the BQ article and didn't know what was causing this before reading this posting, but it has been a tad bit annoying.

    Thanks Velouria!

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  13. The vibrations occur with all generator hubs, but their magnitude varies. The SON 20 probably were the smoothest of all, the current delux is not far behind. On the SON 28, you can notice the vibrations at certain speeds. The Shimano high-end hubs have more vibrations. I haven't ridden the lower-end hubs.

    The speed and magnitude of the vibrations appears to correlate mostly to fork stiffness. On my Alan cyclocross bike with flexible aluminum forks, the vibrations were very pronounced. Another factor is the load you put on the hub - riders with dual headlights have more vibrations than those who run a single LED headlight and a small taillight.

    The vibrations aren't dangerous, but as somervillian pointed out, they can make your hands go numb if you ride long distances at the "vibration speed." I wouldn't worry about vibrations above 25 mph, but on a test bike, we had vibrations between 17 and 19 mph, and that is where I ride most!

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  14. The vibration may not be mechanical in nature, so changing tightness of the cup/cone may be a way to dampen it or change the speeds at which it appears. Same with quick-release (or in the case of Schmidt allen bolt) tightness.

    I would guess the vibration has to do with distinct magnet positions making a standing wave. The hubs have distinct positions where the magnets are and it's apparent when one turns the wheel slowly, or better yet the axle on an unbuilt hub.

    Incidentally, the weak 2.4W hub brake dynamo from Sturmey Archer does not vibrate up to 35mph. I would need to find a bigger hill with less side-streets in the city to test my Pashley at higher speeds. :)

    I've known about the Shimano issue for a while, but it's news to me that SON hubs vibrate as well. This sounds like something to take up with the manufacturers.

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  15. My sam hillborne with son28 hub also does this at high speed, although it's not severe enough to bother me. The "notchiness" that you feel if you take the front wheel off and try to rotate the axle with your fingers is necessary to the principle that makes it work, coils moving past a fixed magnet. I think the fork has as much to do with it as anything, the steel Rivendell fork has a flexible snappiness that I think transmits this well. i'm sure you've noticed ho much the fork will flex over rough pavement.

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  16. I can feel my DH-3N80 hubs on all bikes where I have used them. On very smooth roads and in combination with a stiff fork the vibrations are even just noticable with the lights off. Lights on they become quite obvious and annoying on long rides (several hours).

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  17. My daily commute bike has a Schmidt hub, which powers both a headlight and a tail light which I leave on all the time. The frame is a lugged steel frame with a steel fork (custom frame, made by Peter Mooney). My average commute speed is about 15mph, and I rarely travel much above 20mph, but have never noticed a vibration in the handlebars of this bike.

    One of the things that I love about bicycle commuting is the smooth, silent way that I can move - even if there was no practical reason (i.e. nerve damage or control difficulties) that made vibration bad, I would be very disturbed by it.

    As an engineer, I suspect that any dynamo hub will generate a certain amount of vibration as the wheel turns, and that at certain speeds, this will resonate with the natural resonant frequency of the fork, which will make for a vibration that could be felt, but I have never experienced it.

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  18. My first hub dynamo was an earlier Shimano, not sure of the model, it was one of their less efficient ones, as I recall. It did buzz a bit. And like most anything factory supplied, it came with the bearings adjusted too tightly. Which is particularly troublesome because it's hard to tell with a hub dynamo.

    I upgraded to a Son 28, it's funny, I only notice the buzz in the day, if I've forgotten to turn off my lights. Same speed on my return commute, but I don't think about it at all. Or I didn't until your post; I wonder if the buzzing will drive me bonkers tonight!?

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  19. The vibration may not be mechanical in nature, so changing tightness of the cup/cone may be a way to dampen it or change the speeds at which it appears. Same with quick-release (or in the case of Schmidt allen bolt) tightness.

    I would guess the vibration has to do with distinct magnet positions making a standing wave. The hubs have distinct positions where the magnets are and it's apparent when one turns the wheel slowly, or better yet the axle on an unbuilt hub.


    Yes, exactly, MDI. That's what I was alluding to above, that the SON delux puts out less AC current at a given RPM than the other hubs. Ergo, the vibration is output-dependent, and that is in turn dependent on the strength of the magnetic induction. That's what's being felt as you spin the hub, the alternating attraction and repulsion of the magnets which generates the AC current. I doubt it's a bearing issue, but just mentioned it because it may affect how the vibration is transmitted to the fork.

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  20. I have a Breezer Uptown with a lower- priced Shimano dynamo (The DH-3N30 I think) and have never noticed a vibration at speeds up to 25 mph. Tires are 26x1.75 and the fork is a hearty chromo steel.

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  21. Has anyone experienced the vibration with a carbon fork?

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  22. I run a Schmidt on a carbon fork (old Cannondale) and I haven't experienced any of that sort of vibration. But I wouldn't go out and replace a fork over it. They don't really make heavy duty carbon forks, and were I buying new I'd probably not opt for one.

    -Jeremy

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  23. Wow, I am surprised to know that people run dynamo lights with carbon forks!

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  24. Mark said...
    "As an engineer, I suspect that any dynamo hub will generate a certain amount of vibration as the wheel turns, and that at certain speeds, this will resonate with the natural resonant frequency of the fork, which will make for a vibration that could be felt, but I have never experienced it."

    VERY true. Chasing down the root cause of speed vibrations can be a nightmare not easy to resolve.

    Anything ,and everything, involved at the speed where the vibrations can be felt will pile on their own harmonics to the felt vibration. Solve one and the others get worse.....it can drive you crazy!

    So as I see it the simplest thing to do is wear anti-vibe gloves, change out the hub (and hope it solves the problem), ride just under the trigger speed, or ignore it.

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  25. MelissatheRagamuffinAugust 4, 2011 at 1:47 PM

    I think I've seen exactly one hub generated light system locally, and I didn't have time to closely inspect it.

    I use rechargable battery operated lights. I have lights on my helmet and on my bike. I have a charger at home and at work. But, I could see that the hub generated lights might be nice when you're on a tour and might not be stopping places that will let you plug in.

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  26. Why not swap the wheels between the bikes and see what happens. If you want to control for more, use the same tires you had on the Sam as well. Maybe even the same lamp. For science!!!

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  27. It would be a major pain to swap the lighting for the sake of experimenting, as the Randonneur's is pretty thoroughly integrated. Plus I am a little exhausted of science to tell the truth : ) Looking forward to *not* test riding any more bikes at this point!

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  28. Personally I'd swap it out for standard leds/hub on a bike you intend to cycle at serious speed.

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  29. "I suspect that any dynamo hub will generate a certain amount of vibration as the wheel turns ..."

    Ok, this might be a bit technical, but I wonder if a hub could be designed so that it would contain two sets of magnets and two coils, like the innards of two hubs side by side. The poles of the two magnet assemblies cold be set pi out of phase with each other, so cancelling the vibration. This might work....

    John I

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  30. On my Boulder Bicycle I've got a Son 20R (supposedly it's identical to the SonDelux) mated to an Edelux headlight as well as a B&M tail light. I can't detect anything at any speed with the lights off. When riding on the hoods with the lights on, I can detect a very subtle vibration that seems to start around 17 mph and it increases in intensity as the speed increases. It's mild enough that I forget about it after a minute or so, and now that I've had the bike a while there's times when I don't even notice it.

    What seems odd to me is that I only really feel it when riding on the hoods. If I move my hands to the top of the bar, the ramps, or to the drops, it's hardly noticeable. I'm not sure why that is.

    The tires are 650B Hetres, and the steel fork is pretty flexible as far as I can tell.

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  31. 'It is disappointing to learn that I am limited to cycling at speeds below 17mph if I want to have the lights on without my handlebars vibrating."

    I don't know about you, but if I'm bicycling in situations where a light is needed I'm most likely not going over 17 mph for more than a moment. My average speed on all rides is, sadly, much less than 17 mph.

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  32. Your experience is interesting. I built up a wheel with the Alfine hub for my Globe Live3 this winter and have riden at those speeds on several occassions and not had the same vibrations. I am sure that the geometry is different that your bike and maybe the 32x700 wheels and tires on my bike play a part in it's not getting the harmonic effect. It is interesting that in my experience with motorcycles, simple tire pressure adjustments can improve high speed wobbles that some motorcycles have when tires or headset bearings are worn. Maybe adjusting the tire pressure will improve your wobble as well.

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  33. I have a very subtle vibration and slightly more friction when I turn on my lights, but it is unnoticeable on all but the smoothest of road conditions, when going downhill at a fairly high speed. It is so unnoticeable, I run my lights all the time.

    I'm running a Shimano DH-3N80, with a Philips Saferide LED light. Lightly loaded Rivendell A.H.H.

    It's a resonance interaction, and it occurs at certain multiples of speed that correlate with the number of magnetic notches in the dyno. The magnetic notches get stronger on current draw, and can vary with the A/C to D/C converter capabilities of the light. It's very complex to try and deal with since the harmonics are different for every setup.

    I'm probably just lucky that I don't seem to have a resonant frequency that my bike magnifies much.

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  34. Hi Everybody...
    Does the load have any effect on the strength of the vibration? I'm just wondering if there would be a benefit to having a choice between a few levels of brightness to at least reduce the effect when you don't need all the watts. I really don't know much about hub generators(or any generators for that matter) but it's pretty interesting...

    Walt D's comment about chasing vibrations reminds me of how much fun it is to get a pesky vibration under control. I've built some hot-rods and other fast cars and when I was too poor to have driveshafts made professionally I would just shorten a longer one myself or build one out of pieces, some of them ran smooth and true and some were sorta, uh, buzzy. I would add a couple of hose clamps and mount them in different positions till I felt it getting better than I would fine tune their position till it wasn't too bad. Sometimes you can shift the offensive period up or down the scale to somewhere out of your operating range just by changing something simple.

    There might be a way to reduce the buzz in the handlebars by inserting a damper in the bars(If I was an engineer I would be compelled to mention here that the term is "to damp", with a "damper". A gardenhose is a "dampener". But luckily I'm not an engineer so I don't have to). They are pretty common in motorcycle handlebars and I've wrapped a few around the steering shaft of some racecars. They need a certain amount of mass so sometimes get heavy. I know of one mountainbike racer in the old rigid bike days who squirted a few ounces of silicone or a "snake" of modeling clay into her bars and reported a big improvement.

    Helpful?

    Spindizzy

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  35. I only have used Sturmey Archer generator / drum brake hubs: a 3W which I now installed on my wife's bike and a 2.4W on my Pashley. I didn't experience vibrations with any of them but the max. speed I reached was around 40kmh (25 mph) for short periods.
    If this is a problem of fork resonance caused by the hub there are 2 remedies:

    The harder: Trying to raise the fork resonance frequency by loading it more. (front rack or anything that puts more weight on the front...)

    The easier: Introducing some damping by lowering the front tire pressure.

    I would start by taking 10 PSI off the front tire.

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  36. Anon at 4:45 is on the right track. Tire pressure is the easiest but some other variables are not hard. Bicycles are more sensitive to all this stuff than are motorcycles.

    First I would double-check the centering on the front wheel. Probably it was right when new, it may have shifted. Even these vibrations could have changed it.

    There should be someone at Harris who has a good eyeball for a 10-second frame alignment check. The eyeball kind, not the steel table kind. Any bad alignment would magnify a small vibration.

    Front wheels tolerate a range of spoke tension more than do rears. You could try backing off each spoke 1/4 turn. Even less. Or tighten them.

    Different gloves? No gloves? New tape? All would change the harmonics.

    If the hub runs well enough you can ride around not even knowing it's on, it can't be that awful a hub. Anything that moves it 1% in a good direction may be enough to make it a great hub again.

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  37. If I was an engineer I would be compelled to mention here that the term is "to damp", with a "damper"

    Phew! Good thing you're not, 'cuz you'd be wrong, spin.

    Oh, and if I were an English teacher, I would be compelled to mention that "If I was" is the indicative use of the term, whereas the subjunctive form ("If I were") would have been the appropriate form to describe the untrue-- you being an engineer. But luckily I'm not an English teacher so I don't have to.

    Sorry, couldn't resist. :)

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  38. You know, if the dynamo could somehow be crank-mounted, the vibrations would come through the saddle. Ooooh la la !

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  39. John I - a two phase alternator does not get rid of the problem, it needs to be three phase. This is why all large electrical machines are three phase. Since the torque varies as the sin of the shaft angle, a three phase system has the property that, for any shaft angle, the sum of the torques is zero. For any angle theta, sin(theta)+sin(theta+120)+sin(theta+240) = 0. Try it and see! The torsional vibration inducing torque cancels out leaving just the torque due to the electrical power being generated.
    Of course this only works if the current being generated is sinusoidal. I suspect most LED lamps will only take current near the peak of the voltage waveform, as they use a rectifier to convert to DC, and a controlled current source to drive the LED. Even on a single phase alternator, this will make the problem worse. A halogen bulb will be more nearly sinusoidal, but as it takes more power, it probably balances out. I can easily see two LED lamps making the problem worse.
    A small wheeled bike will have a higher torsional torque frequency, which is probably going to be better absorbed or filtered by the forks, although the lower wheel mass and shorter fork length will raise the resonant frequency. Certainly I have never experienced this on my Brompton/SON setup. Aluminium forks definitely transfer more vibration, including from the road surface.
    Fun, isn't it?
    Max

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  40. Somervillain, sorry if I was being pedantic, at least in the aviation and automotive fields the whole "damp v dampen" thing is a big deal. I just looked back through my Airframe-Powerplant Mech. handbook and test study guide (admittedly from 1983) and the term is always to damp with a damper. The literature/service info that came with the Fluidamper harmonic balancer I recently put on my Mazda rotary powered Lotus 7 clone goes to great lengths to make the point as well.

    I got it drilled into my head by a particularly unpleasant Mech. Engineer while I was working as a fabricator/welder in a robotics prototype lab. So if I'm wrong the sting will be lessened by knowing he was too.

    Spindizzy

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  41. How can the Japanese ever match good ole German engineering...rode a SON for a number of years now and never had your problem.

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  42. I expect high speed vibration arises from the LED control circuit not the generator as such. At higher speeds the generator will produce too much power & the control system will briefly disconnect, reducing rolling resistance, then reconnect. Try the same generator with an incandescent light.

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  43. Play with tire pressure. I have both a Shimano and a son; changing the psi made a difference w both. The son buzzes more; I'd guess because it's on a bike that has a very flexy fork. The buzz feels more like a subtle change in paving material.

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  44. can't believe you posted h20's lame anti-japanese remark. have you contacted shimano for comment on this? i would be interested to know what they have to say.

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  45. Just re-read the comment you refer to and it doesn't strike me as intended to be offensive. But for future I ask h20 and others to please refrain from comments that could be construed as national slurs.

    I have not contacted Shimano about this or the myriad of other issues I have experienced with their (as well as other manufacturers') components; could spend all my time doing just that!

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  46. Velouria,

    My Shimano dyno vibrated noticeably when I first got it. Now, 30 000 or so kms later I guess I do not notice it. FWIW I think this is just one of those things that dynamos do and not linked directly to what you might have paid for it.

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  47. Good info, need to check whether I have got the same problem.

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  48. I have a Sturmey drum/dynamo hub that doesn't have any noticeable vibrations. It has cartridge bearings and is on an old english three speed.

    My shimano disc brake dynamo hub has significant vibrations at speeds over 18 mph (with a 20" wheel). It is on a cargo bike. the frame is long enough that the vibrations start resonating and start shaking the handlebars considerably. If I let go of the handlebars, the problem is reduced.

    I would certainly be interested to see if the SRAM dynamo hubs have the same issue, but not much chance of them coming to the US in any great numbers.

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