Aftermarket Horns FAQ
compiled & edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.
OK, so where is the OEM Horn?
Inside this little Box with the Vents, under the Beak Fender, would you believe. Another reason to get a low fender?
This second photo is from Wunderlich, shows the GS with the Beak Removed and a Cover Plate where it was.
Well If You Can't
See Me, You're Gonna Sure Hear Me!!! (FIAMMS)
April 18, 2000
An improved horn is an inexpensive safety addition that any F owner should be able to install in under 5 minutes. After looking at several brands, I chose to go with FIAMM. The horn I picked fits perfectly in the stock location and utilizes the bikes standard wiring harness with no additional relays. The horn is their "C" model, which is rated at 130 dB and blasts a High Note. And what a high note it is. This horn is infinitely louder than stock and is sure to scare the you know what out of the next cager who cuts you off. You should be able to pick one up at most automotive stores including your local Pep Boys. I got mine for $12.99 plus tax.
Here are a couple of things to consider. First, I originally installed two horns. The only additional work I did was to install one of the FIAMM mounting brackets and a splitter on the wiring harness. The two horns fit side by side. Essentially, the second horn ends up completely opposite to the first horn -- 180 degrees away rotated about the bracket mounting bolt. There was no interference at full lock of the handlebars or at full compression of the suspension. This produced an even louder sound. However, without wiring a relay, I was afraid of overtaxing the wiring system or horn switch. So, I went back to one horn. I don't recommend two, but that's sort of an off the cuff suggestion. I don't have any calculations to back up my theory. Second, just to get an idea of how loud 130 dB's is, here are some values out of a physics book I pulled off my shelf: Jackhammer (at 1 m) 90 dB; Rock Group 110 dB; Threshold of Pain 120 dB; Jet Engine (at 50 m) 130 dB; Saturn Rocket (at 50 m) 200 dB. Any way you slice it, the horn is LOUD.
by Flash #412
When mounting aftermarket horns, in order to reap the full benefit of their louder sound, you should use a large gage wire from the hot terminal of the battery, though a 10A fuse, up to a relay near the horns. Also use large wire from the relay to the horns and the horns to a good, solid ground point.
I mounted the pair of FIAMM's and the relay up under the fairing. The relay
fits along the left side of the steering head, tucked in near the Speedo
cable, mounted to an existing bolt. The horns... after a lot of fitting and
farting, I figured out that you can mount their brackets to the two bolts that
hold that little plastic cover mounted to the bottom of the triple tree.
Positioning the horns on their brackets is tricky. The trick is in getting
them profiled so that they do not foul the fender at full compression. You
need to mount them with the stud up, with the snails curving from back of the
bike, toward the sides, to the front. You'll probably be bending the brackets
Note: BOTH of my FIAMM brackets failed. I am glad that I installed HEALTHY ground wires to each of the horns via a ring-lug at the stud. Neither was lost. One, I remounted with the stock BMW horn bracket, which is NOT available as a separate part. This actually fits better than the stock FIAMM part. The other I remounted with a bracket from a Ducati.
Feedback on all Horns:
Additional Notes on Horn Installation
Flash #412, Mark #403, Andy #982
Where to buy Parts (Relays, Wire):
Horn Wiring Details :
Do not ground stuff back at the battery. Ground it to the *frame* as close to the STUFF (e.g. Horn) as possible. 12 gauge wire should do just fine.
Troubleshooting Horn Installations:
I have installed twin FIAMM's with heavy wire and a relay from radio shack. I get a strong, loud blast when I do a short beep, but when I let the blast continue it deteriorates into a muffled murmur. (this is when I am underway at highway speeds).
I use a low and high note horns with relay and fuse, directly from the battery. No concerns about frying anything and love to hear the bike horn louder than most economy box cages. Also believe I use the horn less now.
You can buy a 12V 30A (12 volt, 30 amp) relay at radio shack (i think it even said horn relay) for about $5. 4 wires on the relay. positive in, negative in switch in and positive out. positive in should come from battery. negative in can come from anywhere negative, including battery (it just actuates the relay switch so current is not an issue). switch in comes from the switch (I think it's positive), and positive out goes to the horns. negative to the horns straight off battery. So, negative from battery to horn. positive from battery to relay (in) to relay (out) to horn. and then you have negative in to relay and switch in to relay which actuate the switch inside the relay. Go get the part from radio shack.
If you don't install a new set horns with heavy gauge wire (directly to the battery via a fuse) and a relay, then don't bother getting them at all. Flash #412
Do not ground stuff back at the battery. Ground it to the *frame* as close to the STUFF as possible. 12 ga should do just fine. Flash #412
Be careful when you screw the horns down. If you put too much torque on the bolt, you will suppress the horns ability to resonate (assuming you don't have a snail shell horn). MichaelC, if you installed the FIAMM's and they aren't loud, check that you didn't overtighten the assembly. Scott C. #345
The BMW R series horn is massively better than the F's and just bolts on. Get them from Motorworks or Motobins or BMW (if you don't already have a mortgage). M+P and MPS sell the twin electric FIAMM's, but they are always back ordered and don't last the British winter. You also need to mount a relay. My local cheapo car place sells FIAMM Airhorns at 14 quid (pounds) a go. They are far too big for the F, but make my combo sound like the Queen Mary. This freed up the R horn for the F.