I have installed car horns onto my bicycle in addition to custom bike lights.
Car horns can alert drivers of your presence. For example, when they’re about to turn and you’re going straight.
They seem effective. When you honk, drivers often brake their cars even though it’s coming from a bike.
My setup can be found at Instructables. In my setup, the horns and batteries were in the basket and the button was on the handlebar. I used the FIAMM El Grande Horns.
The cost of the materials were:
- Horn button:~$10
- El Grande Twin red electric horns:29.99
- 12V 4Ah SLA battery: $16.95
- 12V 500mA 12BC0500D lead acid battery charger: $29.50
- Terminal block:$5.50
My bicycle used to have the Airzound horn but I switched to car horns almost a year ago. Its advantage over the Airzound are:
- Easier to reach buttons
- Possibly better safety for hearing
- Longer honk duration for a single charge
- Familiar sounds may shorten reaction times of drivers
- Suitability for cold weather
The button should be easy to access because the sooner the driver reacts by braking, the shorter the stopping distance. In my setup, my thumb can be close to the button most of the time when I’m riding. If I see obstructions ahead, I won’t need to spend too much time finding them.
I believe that car horns are safer for your hearing than the Airzound because it doesn’t cause ringing in my ears in the open. Maybe that’s because they’re quieter and deeper. The car horns were tested to be 112 dB and the Airzound 115 dB at one metre.
Car horns last longer. On a full charge, the battery should last a few minutes depending on the battery capacity. With the Airzound, it lasts 8 seconds at full volume.
SLA battery was used because the horns needed plenty of power, and they were affordable and easy to find locally. You need a 12V battery than can handle 12 amps. You can find the information from their datasheets.
If the battery can’t supply the current required, the horn clicks or sound distorted which was what happened when I used Li-ion batteries from Deal Extreme. You need your horns to be reliable.
Lee’s Electronics carry the 12BC0500D smart charger. Smart chargers stop charging when your battery is full to prevent overcharging. To prevent damage to the battery, make sure that the charge is always topped up. How often you should charge depends on the storage temperature and how heavily the battery is used. Batteries lose charge faster at higher temperatures.
The horn button was installed close to the gear shifter. A custom mount was required. You can experiment with pipe clamp, cable ties, duct tape, and foam.
The horns were installed in my basket. For my second setup, there was clearance beneath and I installed them underneath. This saves space in the basket. The wires wereattached to the basket with cable ties to keep them from flexing too much or coming off the basket.
Since the battery is heavy, I used the bar that attaches to its base and the quick release of the wheel. That way, the basket won’t sag.
I used a 1.3Ah battery instead of a 4Ah battery for my second setup. It’s lighter and smaller but still works because it can supply at least 12 amps. The only problem I noticed was that it’s quieter only when the button was tapped. If you can find Li-ion or NiMH batteries that work, you can charge them less frequently, or use them for other accessories because they don’t need to be kept at full charge.
The horns were attached to the basket with cable ties. I drilled their mounting brackets for the cable ties. The horn still worked even though the instructions said not to modify the brackets.
So far, my horns haven’t been stolen or vandalized. They don’t have a quick release mount.
I started using car horns in October 2015. I haven’t noticed road rage yet. Only twice did drivers honk back. Sometimes, bystanders look surprised. There was a situation in which the face of a passenger was contorted when the driver was turning right and I honked.
My recommendation is to use it for safety. For example, I would honk to alert the driver of my presence if he’s cutting me off rather than honk after being cut off. There’s a risk of over-correction when used improperly.
What are your thoughts about bicycles with car horns?