How to aim motorcycle auxiliary lights without dazzling traffic

An auxiliary light pointed too high is worse than no light at all. It lights up trees, it blinds the car coming the other way, and it leaves you with nothing on the road. Here's the adjustment, with numbers.

A 20,000 lumen light aimed at the horizon is a hazard, and the rider who fitted it usually thinks it's working because everything looks bright. What you want is light on the road surface between about 10 and 60 metres out. Anything higher than that is glare you're carrying around with you.

Why aim matters more than output

There's a rule of thumb in car lighting that holds up for bikes: the useful light is the light you can see the road by. A beam thrown at eye height illuminates fog, dust and the tops of hedges. It also reflects most of its energy straight back at you in bad weather, which is exactly when you least need it.

Glare has a second consequence. A driver coming the other way is blinded for two or three seconds, and that's happening at closing speeds that leave no room. It's also the reason auxiliary lights get a bad name with law enforcement.

The wall test

Do this at dusk or in a garage, and it takes about ten minutes.

1. Find a flat, level surface with a wall. A garage door or the side of a building works. A sloped driveway doesn't.
2. Put the bike 5 metres from the wall, upright and on its wheels, not on the side stand.
3. Sit on it in riding gear if possible. Your weight changes the suspension and changes where the beam points.
4. Measure the headlight's centre height from the ground and mark that height on the wall with tape.
5. Turn on the auxiliary lights only, and look at where the top edge of the beam falls.
6. Adjust so that top edge sits at the tape mark, then lower it 5 cm below it.

That 5 cm drop matters. At 5 metres it looks like nothing, but out on the road it's the difference between lighting the road and lighting a driver's windscreen at 80 metres.

The pattern is simple: drop roughly 1 cm for every 1 metre of distance. If you only have 3 metres to work with, use 3 cm and finish the job on the road.

Height and sideways aim

Where you mount the lights sets most of the aim before you touch a spanner.

• Fog lights go low. Below headlight height, as low as you can get them without pointing at the front wheel. Fog sits above the road surface, so the light has to go under it.
• Driving lights can go higher. At or just below headlight height, since you want them to reach further.
• Space them out. Two lights close together read as one light to a driver judging your distance. Wider apart, they read as a vehicle.

For sideways aim, point each light slightly outward, a few degrees. You're trying to cover the road shoulder and the edges of the lane, not the centre line. On a right-hand-traffic road, a touch more to the right picks up pedestrians and animals on the shoulder.

The on-road check

The wall only gets you close. Take it out at night on a road you know, and watch three things.

• Where the hot spot lands. It should be 25 to 50 metres ahead at normal road speed.
• Whether the beam cuts off cleanly or sprays light into the trees.
• Whether oncoming drivers flash you. If they do, it's too high, and a driver flashing you at 3 am is telling you something worth hearing.

Meeting traffic

Then use them the way you'd use a high beam. On with an empty road, off for oncoming traffic and when you're close behind someone. The 120W combo has a wireless switch, which makes that habit easier because you don't have to hunt for a switch on the bars with a gloved hand.

If you'd rather not think about it, run a lower output. The 7000LM fog light pair is a 70W kit with a low, wide beam, which is far more forgiving of a sloppy aim than a 20,000 lumen spot. The 4-inch pods sit at the other end: 1,200 lumens in a true spot pattern, which means they need aiming properly or they'll annoy everyone.

FAQ