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Perfectly exposed

Perfectly exposedPhoto: Daniel Simon
Perfectly exposed
The bike headlight should illuminate the road well without dazzling oncoming traffic. We show you how to set the headlight correctly.

The correct adjustment of the headlamp is responsible for ensuring that you as a cyclist can see well - and so can oncoming traffic. A combination of basic adjustment in the workshop and fine adjustment on a dark road is the best way to optimise the effect of your front light.

The legal situation

The current STVZO § 67, paragraph 3, defines the legal basis as follows: "Bicycles must be equipped with one or two forward-facing headlights for white dipped beam. The headlamp must be adjusted so that it does not dazzle other road users."
It is important that only approved headlights with a test mark, the "K number", are fitted. These headlights have a defined, horizontal cut-off line in the upper edge of their light field to ensure glare protection.

The difficulty with dynamo headlights is that you can only carry out the adjustment with the driving light - the parking light, which is fed from a capacitor after a few hundred metres of driving, is usually not strong enough for this. However, this also depends on the model in question.

In order to generate running light, the front wheel with hub dynamo must be able to rotate freely when the bike is levelled. The simplest solution is therefore to clamp the bike horizontally in the mounting stand (A) and position it two metres away from a wall.

Measure the height of the upper edge of the light emission on the spotlight and record the value (X) on the wall. At a distance of two metres, the horizontal cut-off line of the light field should be at least seven centimetres below this mark. If it is at the same level or higher, the light is dazzling.Photo: Daniel SimonMeasure the height of the upper edge of the light emission on the spotlight and record the value (X) on the wall. At a distance of two metres, the horizontal cut-off line of the light field should be at least seven centimetres below this mark. If it is at the same level or higher, the light is dazzling.

The second step is a practical check: at night, the cut-off line should be just visible, but at the most far in front of the driver behind. The lateral illumination should be symmetrical to the centre.

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The performance of hub dynamos increases at high speeds. This is why the headlights are brightest in the speed range between 25 and 30 km/h. According to the STVZO, however, good headlights must be available from a speed of around 16 km/h.

For optimum light output, drive a few metres in total darkness on a road free of traffic. In the meantime, carefully align the light by hand so that the cut-off line is as far away as possible and just visible on the carriageway in front of you.Photo: Daniel SimonFor optimum light output, drive a few metres in total darkness on a road free of traffic. In the meantime, carefully align the light by hand so that the cut-off line is as far away as possible and just visible on the carriageway in front of you.

Replacing headlights - how it's done

Dismantling the old luminaire

First disconnect the plug connection to the rear light. The area is often insulated with heat-shrink tubing and must first be painstakingly exposed with a sharp blade.Photo: Daniel SimonFirst disconnect the plug connection to the rear light. The area is often insulated with heat-shrink tubing and must first be painstakingly exposed with a sharp blade.
Then pull the plug from the hub dynamo and remove the front wheel. Open the connector housing with a small screwdriver. The cable ends can be easily pulled out of the fitting when the halves are removed.Photo: Daniel SimonThen pull the plug from the hub dynamo and remove the front wheel. Open the connector housing with a small screwdriver. The cable ends can be easily pulled out of the fitting when the halves are removed.Expose the dynamo cable completely. On suspension forks, the cable is usually routed under a bolted strip along the bars.Photo: Daniel SimonExpose the dynamo cable completely. On suspension forks, the cable is usually routed under a bolted strip along the bars.On rigid forks, the cable is often routed inside the bar. If there is a plastic plug for cable routing in the opening, carefully lever it out of the hole, pull it off and set it aside.Photo: Daniel SimonOn rigid forks, the cable is often routed inside the bar. If there is a plastic plug for cable routing in the opening, carefully lever it out of the hole, pull it off and set it aside.Lay a sturdy twisted yarn (or shift cable) about 10 cm long parallel to the end of the cable and glue it tightly.Photo: Daniel SimonLay a sturdy twisted yarn (or shift cable) about 10 cm long parallel to the end of the cable and glue it tightly.Remove the old light from the fork bridge. Pull the old cable upwards out of the fork leg until the start of the thread is sticking out. Disconnect the cable and thread again. The entire length of the thread remains in the tube so that the new light cable can be attached later.Photo: Daniel SimonRemove the old light from the fork bridge. Pull the old cable upwards out of the fork leg until the start of the thread is sticking out. Disconnect the cable and thread again. The entire length of the thread remains in the tube so that the new light cable can be attached later.

Mounting the new headlight

Glue the new dynamo cable securely to the thread in the fork leg. Slowly guide the cable from above while helping it out of the opening in the fork leg by gently pulling on the thread at the bottom.Photo: Daniel SimonGlue the new dynamo cable securely to the thread in the fork leg. Slowly guide the cable from above while helping it out of the opening in the fork leg by gently pulling on the thread at the bottom.
Screw the new light to the fork. It must not be possible to twist the headlight and bracket.Photo: Daniel SimonScrew the new light to the fork. It must not be possible to twist the headlight and bracket.Slide new heat-shrink tubing onto the cable ends and restore the plug connection to the rear light. Attention: You must observe the polarity here! The earth cable is marked white.Photo: Daniel SimonSlide new heat-shrink tubing onto the cable ends and restore the plug connection to the rear light. Attention: You must observe the polarity here! The earth cable is marked white.Activate the heat-shrink tubing with a hot air gun. Caution: Too much heat will cause the cable insulation to tear.Photo: Daniel SimonActivate the heat-shrink tubing with a hot air gun. Caution: Too much heat will cause the cable insulation to tear.Pull the dynamo cable out of the fork hand-tight with a little play on the fork crown. Leave a good 4 centimetres of overhang near the wheel axle, shorten the cable and strip 1.5 centimetres of insulation.Photo: Daniel SimonPull the dynamo cable out of the fork hand-tight with a little play on the fork crown. Leave a good 4 centimetres of overhang near the wheel axle, shorten the cable and strip 1.5 centimetres of insulation.Push the bare ends into the plug and join the two halves together. Connect the cable and hub dynamo.Photo: Daniel SimonPush the bare ends into the plug and join the two halves together. Connect the cable and hub dynamo.Tie any excess cable length to the headlight bracket using cable ties or adhesive tape. Make sure that the cable does not hinder the front wheel from turning from left to right.Photo: Daniel SimonTie any excess cable length to the headlight bracket using cable ties or adhesive tape. Make sure that the cable does not hinder the front wheel from turning from left to right.

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