Dynamo hubs are becoming more and more common on bikes used for bicycle touring and bikepacking. This can be attributed to advancements in LED technology, improvements to the dynamo hub itself and the fact that we all have USB powered devices that we like to charge along the way.
This article will delve into what you should know about dynamo hubs.
Dynamo Hub Types
The most common size for a touring bike is still 9mm quick release, but with axle standards changing both on-road and off-road, we’re now finding touring and bikepacking bikes available with as many as six axle variants.
1. Quick Release 9mm – 100mm
2. Thru Axle Road 12mm – 100mm
3. Thru Axle MTB 15mm – 100mm
4. Thru Axle MTB Boost 15mm – 110mm
5. Fat Bike Quick Release – 135mm
6. Fat Bike Thru-Axle 15mm – 150mm
There are two different common forms of spade connector – the Shimano design and the Schmidt SON design. Neither design can be said to be ‘better’ – they both do the same job of transmitting power up the cable. Due to the market split of connector types, dynamo lights and USB chargers tend to come without any connector attached to the cable ends.
A less common connector design is the Schmidt SL fork dropout. This is a really neat design; the connection happens between the edge of the hub and a fork dropout plate that’s soldered to the wiring. Almost every Schmidt hub is made in an SL version. Unfortunately, you’ll rarely find the Schmidt SL dropout on anything but custom-built forks.
There are three common watt outputs from dynamo hubs: 1.5W, 2.4W or 3W (all at 6V). Given that touring and bikepacking is often conducted at speeds below 25km/h, the most powerful option (3W) is 100% necessary if you’re planning on charging USB devices, and it’s also the best for lighting too. According to the lab testing, there is almost no difference in terms of drag between a 2.4 and 3.0W dynamo hubs. It is worth noting, that 2.4W hubs offer enough power if you’re touring with smaller wheels (16-20″).
Dynamo hubs come with anything from 20 spoke holes for a lightweight carbon wheel builds through to 48 holes for the strongest tandem wheel. Most touring and bikepacking bikes use between 28 and 36 spokes. While spoke count makes some difference, evenly balanced spoke tension across the wheel and a stiff touring rim tend to matter most in terms of strength.
Dynamo Hub Efficiency
If you’ve ever picked up a dynamo hub and tried to spin the axle, you’ll know that they feel incredibly ‘notchy’. This is the result of a series of powerful magnets passing a coil and in turn, creating an electric charge. Interestingly, dynamo hub drag only has a small effect on your speed because of the flywheel effect of a rotating wheel. In THIS article, I calculated the drag to result in an extra three to six minutes riding time over 100km, all while getting a good charge to your electronics (or powering your lights).
Dynamo hubs in conjunction with USB charging units can also provide USB power (5V/500mAh = 2.5W) from 12km/h. The most powerful chargers will even put out more than 5W at 20km/h! The brightest dynamo lights are around 1300 lumens, or more than 100 lux – click HERE to read all about dynamo lighting.
Schmidt SON Dynamo Hubs (3W)
Schmidt is the industry standard for dynamo hubs in terms of efficiency and reliability. These German-made hubs are also the most expensive. Despite this, they’ve been my dynamo hubs of choice since 2008. The bearings are not expected to need servicing until well after 50,000km due to a combination between robust weather sealing and the high-quality SKF sealed bearings – in fact, I’ve never had to replace the bearings in any of my hubs. Included with Schmidt hubs is a five-year guarantee.
Schmidt hubs have been tested to have just 0.25-1.25 watts of resistance (@ 10-30km/h) with a light switched off, which makes them incredibly efficient even when compared to a standard hub. And with a light switched on, they generate the lowest drag of any 3W dynamo hub at speeds over 20km/h.
SON28 non-disc – 32, 36h
SON28 disc – 28, 32, 36h
SON28 Tandem – 40, 48h
SON28 disc 135 – 32h
SON28 disc 135 VR – 32h
Thru Axle – Disc
SON28 12mm – 28, 32, 36h
SON28 15mm – 28, 32, 36h
SON28 15mm Boost 110 – 32, 36h
SON28 15mm 150 – 32h
Shutter Precision SP Dynamo Hubs (3W)
SP dynamo hubs offer very similar performance to Schmidt (in fact, they can be more efficient at low speeds), but without the premium price tag. These hubs are also typically reliable (ok, there’s the odd bearing issue), with the exception of the first generation PD-8X 15mm which has had a 100% electrical failure rate in my circles. Almost all of the disc brake hubs are available with 6-bolt (eg. PD-8X) or a centerlock (eg. PL-8X) brake rotor mount, and the quick release hubs are the only 3W models available for wheels of with low spoke counts, including carbon road wheels (20-24h).
PV-8 non-disc – 20, 24, 28, 32, 36h
PD-8 disc – 20, 24, 28, 32, 36h
Thru Axle – Disc
PD-8X-M 12mm – 32, 36h
PD-8X 15mm – 32, 36h
PD-8X-110 15mm – 32, 36h
PD-8X-150 15mm – 32, 36h
Shimano Dynamo Hubs (3W)
Shimano makes the majority of the world’s dynamo hubs, so it’s safe to say that they know a thing or two about them. The lab testing shows 0.50w-2.50w drag (@ 10-30km/h) when a light is switched off, and 3.50w-7.50w drag when a light is switched on. This is only marginally higher than the Schmidt and SP hubs which are often more than twice the price.
That said, Shimano has just released the DH-UR700-3D model and they’re claiming it has 44% less drag than the previous generations. If this is true, it would match the dynamo performance of a Schmidt or SP hub. The Deore LX and Alfine models are essentially the same, while the Deore XT dynamo hub sheds 56 grams thanks to an aluminium axle and coil. The top-of-the-line UR700 and UR705 dynamo hubs save a further 30-50 grams.
Alfine S501 disc – 32, 36h
Deore LX T670 non-disc – 32, 36h
Deore LX T675 disc – 32, 36h
Deore LX 3N72 non-disc – 32, 36h
Deore LX 3D72 disc – 32, 36h
Deore XT T8000 disc – 32, 36h
UR700 disc – 32, 36h
Thru Axle – Disc
UR705 12mm – 32, 36h
2019: KT Dynamo Hubs (3W)
KT has recently released a dynamo hub range including a hub with a rather innovative end-cap design. By switching out the end-caps, you’ll be able to interchange your dynamo wheel between bikes that employ QR, 12mm or 15mm axles. You can get the hub in either the standard 100mm hub width or to suit 110mm Boost forks, and the disc brake hub models are available with 6-bolt (eg. KD5F) or a centerlock (eg. KC5F) brake rotor mounts. KT hubs employ the same hub shell as the SP Dynamo hubs, although internally they have their own circuitry which is yet to be proven long-term.
KD6F disc – 32, 36h
KV6F non-disc – 32, 36h
Thru Axle – Disc
KD5F 9mm 12mm 15mm – 28, 32, 36h
KD1F 9mm 12mm 15mm Boost 110 – 28, 32, 36h
Other Dynamo Hubs (3W)
Biologic Joule 3 Disc – Re-branded 32h Shutter Precision PD-8 hubs in silver or black.
Exposure Disc – Another re-branded 32h SP PD-8 hubs available in a package with the Exposure Revo dynamo light.
Love Mud Juice Disc – More re-branded 32h SP PD-8 hubs!
Neco Rove Disc – The claims are pretty lofty for this 933g dynamo hub with built-in USB charger – 15W of charging potential (5V@3A). Unfortunately, the testing has shown that you need to be going 50km/h to achieve that figure and that it isn’t at all competitive below 25km/h.
Sanyo H27 Non-Disc – This is one of the best value dynamo hubs going around. Unfortunately, it has a lot of drag compared to other hubs with a light or USB charger switched off.