How I picked these: how they work, specs and buyer reviews. I haven't owned every one of them.
What to expect
- The lights follow your speed. They come on as soon as the wheel turns and reach full brightness at an ordinary riding pace. Walking pace gives a weaker light.
- A standlight bridges the stops. Good modern lamps keep glowing for a few minutes at junctions, from a capacitor charged while you ride. No battery involved.
- There's some drag. A hub dynamo adds a little resistance, slightly more with the lights on. Most riders don't notice it. A bottle dynamo drags more, but only when engaged.
- A hub dynamo is a new front wheel. The dynamo is the hub, so the wheel has to be built around it. That's a bike shop job unless you build wheels yourself.
- Not every dynamo lamp is brighter than a good battery light. The best ones are very good on dark lanes. Their strength is that they're always there and always charged.
Why a dynamo
The most common reason a bike has no lights is a flat battery. A dynamo can't go flat. If the wheel turns, you have light.
A hub dynamo sits sealed inside the wheel. It doesn't slip in rain, doesn't wear the tyre and is almost silent. A bottle dynamo is cheap and easy to fit, but slips when the tyre is wet and whirrs as it runs.
Nearly all bike dynamos and lamps are made for 6 volts, 3 watts. So any 6 V 3 W hub works with any lamp made for it. You can mix makes.
Stopping at a junction in the dark is when you most need to be seen. A lamp with a standlight stores a little energy in a capacitor and keeps glowing while you're stopped.
Lamps approved under Germany's StVZO rules have a beam with a sharp top edge. The light goes on the road, not into oncoming eyes. It's polite and you see more of the road.
The rear lamp takes its power through the front lamp. One switch on the front controls both, and there's only one dynamo to wire.
How it works
A dynamo is a small generator. Magnets turn past coils of wire, and that pushes a current. In a hub dynamo, the magnets spin with the wheel around coils fixed to the axle. In a bottle dynamo, a small roller presses on the tyre and spins the magnet inside.
The dynamo's output swings back and forth in direction (alternating current). The front lamp turns it into a steady supply for its LED, charges the standlight capacitor, and passes power on to the rear lamp.
Two-core cable has two wires, so the current goes out on one and back on the other. Older and simpler setups use a single wire, with the metal bike frame carrying the current back. That works, but paint, rust and carbon frames break the path, so two-core is more reliable.
What to buy
These are affiliate links. If you buy through them I make a small commission, at no extra cost to you. It helps cover the cost of running this site. This is a hobby, not a shop.
You need one dynamo, one front lamp and one rear lamp. Check every listing for fit before you order: axle type, brake type and mounting all vary. The budget range is rough: about £40 for a bottle dynamo setup, and £250 or more for a hub dynamo, good lamps and a wheel build.
Dynamo
Front lamp
Rear lamp
Also needed
Fit it
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Choose hub or bottle
If you ride in the dark often, all year, go hub. If you ride in the dark now and then, or want to try it cheaply, go bottle.
Why: a hub dynamo is the bigger upfront cost but needs nothing afterwards. A bottle dynamo is cheap but you'll feel its limits in wet winters.
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Get the wheel built (hub)
Take the hub, your bike and ideally your current front wheel to a bike shop. Ask them to build it into a rim that matches your tyre size and brake type, and ask which side the hub's electrical connector should face.
Why: the hub has a set number of spoke holes and must be laced to a rim with the same number. Getting the spoke lengths and tension right needs a wheel builder.
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Or mount the bottle dynamo
Bolt its bracket to the fork leg or seat stay. Set it so the roller sits squarely on the tyre's sidewall, with the dynamo's axis pointing towards the wheel's hub. Check the spring presses it on firmly when engaged.
Why: if the roller sits at an angle, it scrubs the tyre, slips and wears quickly. Pointing at the hub keeps it rolling straight.
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Fit the front lamp
Most dynamo lamps mount on the fork crown or a bracket on the fork or handlebar. You may need a bracket to suit your bike. Fit it so it points straight ahead.
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Run the cable to the front lamp
Strip the ends of the two-core cable and connect it to the hub's connector. Bottle dynamos often have a single terminal and use the frame as the return, as in the dashed line in Fig 2. Run it up the fork leg, tied every 10 cm or so, and into the lamp's input.
Why: a loose cable gets caught in spokes. Tying it close to the fork keeps it clear of the wheel and the brake.
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Run the cable to the rear
From the lamp's rear output, run a second two-core cable along the frame to the rear lamp. Match the + and − (or the marked terminals) on both ends.
Why: on many lamps the rear output only flows one way, so the rear lamp may only work one way round. If it doesn't light, swap the two wires at the rear lamp.
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Aim the beam
In the dark, against a wall or on a quiet road, tilt the front lamp so the bright top edge of the beam lands on the road some way ahead of you, not level with the horizon.
Why: aimed too high, a cut-off beam dazzles oncoming people and lights trees instead of the road. Aimed too low, you see too little ahead.
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Test the standlight
Ride for a few minutes, then stop. Both lamps should keep glowing for a while.
Why: the standlight capacitor charges while you ride. If it doesn't stay lit, check the rear wiring and that you rode long enough to charge it.
Riding + care
- Leave it on. Many lamps have an automatic setting using a light sensor, or a daylight running mode. Being seen in daytime is a bonus that costs you nothing to charge.
- Hub dynamos need little care. They're sealed. Keep the connector clean and dry, and check it's pushed fully home after you take the wheel out.
- Bottle dynamos need the roller kept clean and the tyre sidewall in good order. Disengage it in daylight to save drag and tyre wear.
- Check cables every few weeks, especially where they bend at the fork and the rear lamp.
- Taking the wheel out: unplug the hub connector first. Plug it back in before you ride.
Common problems
| What you see | Likely cause | Fix |
|---|---|---|
| No lights at all | Hub connector unplugged, or lamp switched off | Check the connector is fully on. Check the lamp switch. |
| Front works, rear doesn't | Rear wires the wrong way round, or a broken wire | Swap the two wires at the rear lamp. Check the cable along its length. |
| Lights flicker on bumps | Loose connection | Re-strip and re-fit the wire ends. Check the connector clips. |
| Bottle dynamo dims in rain | Roller slipping on a wet tyre | Increase the spring pressure if it's adjustable. This is the bottle dynamo's main weakness. |
| Bottle dynamo loud | Roller at an angle to the tyre | Realign it so its axis points at the hub. |
| No standlight | Not ridden long enough, or lamp has none | Ride a few minutes first. Check the lamp's spec for a standlight. |
Safety + the law
In the UK, between sunset and sunrise, a bike on the road must have a white front light and a red rear light, lit. It must also have a red rear reflector, and amber pedal reflectors if it was made after October 1985 (Highway Code rule 60). The lights should meet the relevant British Standard or an equivalent European standard.
Dynamo lights are road legal when they meet those rules, like any other light. Lamps approved under Germany's StVZO rules carry an approval mark and have the cut-off beam. That's a good sign of a well-made lamp, and it means you won't dazzle anyone. Check the current Highway Code if you're unsure about your setup.
- Check the wheel is secure after any wheel change: quick release closed or thru-axle tightened properly.
- Keep cables away from spokes, discs and brakes.
- Keep reflectors fitted even with good lights. They're required and they work when everything else fails.
Notes
The 6 V 3 W standard comes from the old bulb lamps: roughly 2.4 W for the front and 0.6 W for the rear. Modern LED lamps are far brighter from the same power. Lamp brightness figures in lux, like the IQ-X's 100 lux, describe the brightest spot in the beam. They're a peak figure, not the total amount of light, so a wider beam can feel just as useful.
If you're not confident about the wheel build or wiring, any bike shop that builds wheels can fit the whole lot.
Related guides: wind-up torches and radios, Morse code without batteries, battery-free shortwave radio.