Frequently Asked Questions
Dynamo lights:
Which dynamo headlamp is the best for me?


Dosun U1 Herrmans H-One S Herrmans H-Diver


Dosun U1
For spirited cycling requiring all-around performance, our favourite is the Dosun U1. It has the rare quality of achieving high intensity in beam pattern (50 LUX), while at the same time virtually eliminating the dreaded “dark region” between front wheel and the beginning of the beam pattern. Until recently, cyclists relying on high powered LED dynamo headlamps have come to accept the dark region as a necessary trade-off for high LUX ratings, which enable beam patterns to project further down the road. The existence of this trade-off relates to complex technical challenges in designing, fabricating and producing small optics for high-powered LEDs. In largely overcoming this tradeoff, the Dosun optic is a hard-won technical achievement that was paid for with old-fashioned sweat and effort.
Herrmans H-One S
For fast riders demanding a beam pattern that will project the furthest down the road, the Herrmans H-One S is the one for you. It has the highest LUX rating of any hub dynamo lamp that we are aware of. The trade-off for the massive 95 LUX measured rating (w/o tail lamp) is a noticeable dark region between the front wheel of the bicycle and the beginning of the beam pattern (this dark region is consonant with that of competing high LUX rated dynamo headlamps we have tested). Confident riders needing to see as far as possible down the road when travelling at high speeds will be pleased with the raw power of the Herrmans H-One S.

A notable feature of the H-One S is the unusually warm colour of its LED. Not quite neutral by our reckoning, the light it emits but is noticeably warmer than other headlamps we carry as well as most on the market. LEDs in the cool white end of the light spectrum currently dominate the market for portable LED lighting products due to their higher lumens output per power input (advertising number) in comparison to their warmer hued counterparts. The technical literature suggests that warmer hued LEDs may in practice be more versatile despite marginally lower lumens output. This is because they often provide better illumination in wet conditions and apparently allow the elderly to see more clearly at night than with cool white hues.
Herrmans H-Diver
For leisure cyclist, the Herrmans H-Diver is the lamp for you. It is has:
Despite its modest 20 LUX rating (meaning that the beam pattern not shine as far down the road as other dynamo headlamps we carry), the H-Diver illuminates a much wider swath of road immediately ahead of the cyclist more brightly than other high-powered dynamo headlamps. It is our top pick for cycling at recreational paces because it noticeably inspires cyclists’ confidence with a bright and generous beam pattern in the near and peripheral fields.  

How weather resistant are dynamo lamps?

Herrmans H-Track Spanninga Pixeo
All products carry by IDC are designed to withstand riding in wet conditions. To our knowledge, no dynamo lamps at any price level are designed to be “waterproof” in the sense that they can be submerged. In terms of moisture, the weakest point of most dynamo lamps is where wiring extends from the electronics inside the housing to the outside. This is normally at the bottom of the lamp where direct exposure to rain is not expected. For bicycles without mudguards, however, the standard mounting point of dynamo headlamps (i.e. fork crown) may not be optimal - particularly if regularly ridden for extended periods under wet conditions. This is because spray from the front wheel will propel water directly towards the underside of fork crown mounted headlamps. For bikes regularly ridden in wet conditions, we highly recommend mudguards to reduce spray directly onto the underside of both front and rear lamps. That said, quality dynamo lamps (like those we carry) have been known to last years on bikes without mudguards despite exposure to wet weather rides.

All dynamo lamps we carry are also designed to withstand outside storage employing aluminum and highly weather and UV resistant plastics for their housings. We advise customers to seek out covered outside storage whenever possible as reducing direct exposure to the elements is likely to improve the longevity of our products. We have lamps that have been operating trouble-free for well over four years under covered outside storage conditions.

How do I charge my USB devices
with a hub

Hub dynamos cannot directly charge USB devices because they produce AC (not DC as required by USB standard products). Perhaps more important is the fact that the power produced by hub dynamos is unregulated (meaning that output varies by the speed of the bicycle). At high speeds, directly connected electronic devices that are un- or under-protected from overvoltage could be damaged. To charge USB devices, you would need to purchase in addition to the hub dynamo one of a small number of products on the market designed specifically to allow hub dynamos to safely charge USB products. IDC is actually developing some pretty neat stuff for USB charging but these products are not yet ready for mass production.
There are a small number of products currently on the market that enable USB charging via hub dynamos that we have personally tested and recommend. One is the PedalPower product produced offered by an Australian company. The other sleeker (more expensive) item called The Plug is produced by a German company Tout Terrain. The websites for each hyperlink can also accommodate purchase and facilitate delivery worldwide so you can source directly from them.
I have not yet tested the LightCharge product, but it looks promising and is reasonably priced. Early reports suggest that its peak power output and thus potential rate of recharging is lower than the previous two products.
A nice overview of other hub dynamo specific charging solutions is provided on the Cycling About website. If you can read German (or use Google translate), an even more extensive list of USB charging from hub dynamo solutions can be found on this page at radreise-wiki.de.

Although there are numerous DIY hub dynamo USB charging solutions on the interet, Sean Michael Ragans article in Make Magazine caught my eye for its conscious effort to support even novice electricians to build the Pedal Power Phone Charger. I may try one by myself at one point but would be glad to receive feedback from anyone that tryes on which I could share here.

But, if you would like to have the best dynamo/USB charger that we have tested to date in terms of increasing the charge on a smartphone with backlight on while running power-hungry GPS applications, the Sinewave Cycles Revolution is our current favorite!

Shutter Precision hub dynamos
Do SP hub dynamos have inbuilt overvoltage protection?

SP hub dynamos do not come with overvoltage protection because quality LED dynamo lamps (like those we carry) come complete with inbuilt overvoltage protection. If you added overvoltage protection 
(Shimano does make such a product) between a hub dynamo and a modern LED lamp intended for use with hub dynamos, you would end up with a dimmer lamp that is no more reliable.

How often do SP hub dynamos require service?
SP hub dynamos employ sealed bearings that do not require service until the bearings require replacement. We already have customers that have logged over 10,000 kms without any problems and we expect that under normal use the service life of these bearings should be well over 20,000 kms. Should they ever need servicing, they can be sent back to SP and replaced with new ones for roughly USD 30 including the cost of return postage.

Are SP hub dynamos user serviceable?
Alas, SP hub dynamos are not user serviceable and indeed we are aware of no hub dynamos that are based on manufacturer’s recommendations. Any attempt to service an SP hub dynamo will void its two-year warranty. We have received quite a number of requests from consumers on how they might service their hubs even accepting that attempting to do so would void their two-year warranty. They accept this risk thinking that this would save the need to disassemble and rebuild the wheel. Unfortunately, the design of SP hub dynamos like that of many other brands requires disassembly of the wheel for bearing replacement. Furthermore, the delicate generator mechanism housed within the hub body must be re-calibrated to tolerances of less than a millimetre each time bearings are replaced. Failure to carry out this operation properly (which is likely without expert knowledge, experience and tools), will generally result in catastrophic failure of the generator mechanism after a period of use. SP engineers have considered making their hubs user serviceable (with much prodding from IDC at the behest of our technically savvy testers). But the expertise and equipment required to carry out recalibration of the generator mechanism each time the bearings are replaced presents a technical hurdle that SP engineers, and indeed all other hub dynamo manufacturers we are aware of, have so far declined to attempt.

I just received my SP hub dynamo and it feels like the bearings have been over-tightened.
If you have not used hub dynamos before, the “notchiness” you feel when turning the hub by hand will feel very much like that of overly tight bearings. Please rest assured that this is normal and your bearings are not over-tightened. SP hub dynamos use sealed bearings that technically speaking cannot be over-tightened or even adjusted for that matter. Please do not try to adjust SP hub dynamo bearings as doing so will void your two-year warranty. It is not possible to adjust the bearings on your SP hub dynamos and indeed attempting to do so will normally sever a small but critical wire rendering the hub dynamo unserviceableThe reason for the notchiness is that hub dynamos rely on small but unusually powerful magnets revolving around a coil to generate electricity. While the number of poles (points where magnetic attraction would like to settle throughout rotation) varies by maker and hub specification from 24 to 32, all hub dynamos exhibit notchiness due to similarities in their basic design. When hub dynamos are unlaced and turned by hand, resistance is noticeable. When laced up to a wheel and ridden on a bicycle, the actual resistance is very low and indeed most cyclists do not notice any difference between a modern dynamo versus a standard front hub while riding. This experience can be generally verified (of course not without exception) via a Google search of “drag hub dynamo”. A good overview of how the friction from hub dynamos can affect long distance riders can be found here. The upshot of the last article is that your choice of tyre (even among high-performance skinny ones) is manyfold more important than the drag you experience from a hub dynamo.
I already have a Shimano hub dynamo and the SP seems to be “notchier” than  Shimano hub dynamos?
Yes, if you compare directly an unlaced SP hub with a Shimano or a Sanyo, it will seem more notchy. This is because the magnets are higher quality and stronger. What you are in fact experiencing is a peak magnetic pull (point of closest distance between the magnetic poles and yoke) that is sustained for a shorter part of the turn on an SP hub dynamo in comparison to other brands, which sustain a weaker magnetic pull for a longer part of the turn between poles - due ostensibly to their use of lower grade magnets. If you try a SON, you will also notice stronger notchiness than the Shimano and similar to the SP, because the magnets are similarly higher grade. SP, as well as independent tests results and the experience of IDC staff, verify that when the wheel is built, overall resistance and vibrations are lower with an SP than with the Shimano, Sanyo and SON.
Which Shutter Precision hub dynamo should I use for my 20” or 16” wheel bicycle?
We at IDC generally recommend the “P” series hub dynamos even for small-wheeled bikes as they produce more power at lower speeds than “S”, which are designed to produce 6V 3W with 20” and 16” wheels at 15km/h (9.3mph). The weight and resistance penalty are in practice negligible. Using P series hub dynamos designed to produce 6V 3W with slower turning (fewer rotations per distance travelled) 700c and 26” wheels at 15km/h on 20/16” wheels translates into brighter lights at lower speeds and more power for USB device charging - which is a rapidly increasing use for hub dynamos. One thing to look out for is making sure that your 20 or 16" wheel is 100 OLD, i.e. that you have 10cm of space between the front fork of your bicycle. If you have a Brompton or a Dahon branded bicycle, you likely have a 74mm OLD (i.e. 7.4cm spacing between your fork blades) and would thus need to purchase the SP hub dynamo designed specifically for your brand.

Which Shutter Precision hub dynamo is best for my 700c/26" wheeled bicycle?
IDC recommends PV-8 series hub dynamos because they generate more power than the SV-8 series hub dynamos, which are actually designed for 20 and 16" wheels (see above). Competitive riders sometimes choose SV-8s because they are marginally lighter and have slightly less resistance. They accept lower power output (particularly at low speeds) mainly because they normally ride faster and thus generate sufficient power at the speeds they normally ride at. In reality, both PV-8 and SV-8 hub dynamos provide sufficient power for safe riding at night with modern LED headlamps - like those I sell. But I personally weight power (i.e. brightness) particularly at low speeds enough that I use a PV-8 even with on my 20" wheeled Bike Friday folding bike. As USB device charging continues to gain interest as an application for hub dynamos, the extra power is in our view a good "precautionary" investment.
What length spokes should I purchase to build a wheel with an SP hub dynamo?
The spokes you need to purchase depend on your choice of rim, lacing pattern as well as the PCD (circle pitch diameter) of your SP hub dynamo which can be found here. The United Bicycle Institute of Ashland, Oregon generously shares an on-line calculator for spoke length taking these three variables into account, which customers have provided good feedback on. We have also received a strong recommendation from Kerry at k-Lite for Edd as a very reliable calculator.
How does the switch on the Switchable SP hub dynamo work?
A video presentation can be seen here.
Can I mount and use my SP hub dynamo in reverse?
The official line is that SP hub dynamos should not be mounted in the reverse direction, i.e. with the connector on the left as opposed to the recommended right side your bicycle’s front fork. You can also confirm correct directionality by the chevrons laser etched on the hubs which should turn in the same direction as the wheel when riding.

The generator mechanisms are designed to be more efficient when rotating in the recommended direction though in practice the difference is relatively minor. That said, IDC has been told informally that reverse mounting should not be mechanically unsafe, of course, we would certainly not recommend it.
What if my disc brake is a non-standard configuration requiring the disc to be mounted on the right side of the bike?
In terms of mounting the hub in reverse, the official line is that it should not be mounted with the disc tabs on the right side of the fork. That said, IDC has been told informally that doing so should not be mechanically unsafe. Although IDC certainly does not recommend reverse mounting, users doing so at their own risk should bear two factors in mind. 1) The dynamo is more efficient (i.e. has less resistance) when rotating in the manufacturer’s recommended direction. 2) The disc bolts are angled to enhance stiffness when the hub is mounted in the correct direction so users may experience reduced braking performance when SP hub dynamos are mounted in reverse.
The connector on my SP hub dynamo is plastic and I am concerned that it may not be durable.
Multi-year experience here at IDC is that the SP connector is robust and well designed. Ours have stood up well to years of outdoor exposure (notably the SP and Shimano hub dynamo connectors are interchangeable). When the bare wire is folded back and the inner plastic clip is clicked into place on these connectors, they grip the wire well. If you un-mount your front wheel forgetting to unclip the connector, it normally comes off without disturbing the attached wiring or sustaining damage. This apparent design feature is has been rigorously tested via hands-on “inexperience” dismounting front wheels whilst forgetting to unclip the plastic connector. If you have a 3D printer you can also use print
spares with a file available here: http://www.thingiverse.com/thing:132703.

SunUp Eco Generator

Can the SunUp Eco DS-1R be mounted on the front wheel of my bike?
The difficulty with front wheel mounting of the SunUp Eco DS-1R is spacing. There is normally not enough space between the axle flange and the fork blades for the generator to be reliably mounted. This makes developing a universal and dependable fit for the front wheel very difficult from an engineering standpoint. The folks at SunUp Eco have developed a prototype front wheel generator, but the requirement for a special SunUp Eco front hub obviated its natural advantages over standard hub dynamos.

That said, the SunUp Eco DS-1R has been successfully mounted on the front fork of Surly Moonlander which as a 135mm axle. For more information about this application, you may write Kerry at K-Lite.

What is the best way to wire the lights on by hub dynamo lighting system?
IDC has produced a note with photographs on wiring hub dynamo based lighting system accumulated over years of experience.
Is the valve hole for the Sanyo/Vuelta hub dynamo wheel Presta or Shrader?
These wheels are drilled for Shrader (larger diameter automotive style valve. To use Presta valve inner tubes with these rims we recommend purchasing and fitting a valve adaptor from your local bike shop. Should your local bike shop not have them or if you do not have a local bike shop in your area, adaptors are also available via larger online bicycle parts retailers with customers reporting that good pricing can be found on Amazon. Our own experience is that using a Presta valve inner tube with a rim drilled for Shrader without and adaptor can work fine in a pinch.