Train Horn Without Deleting Your Spare Tire: Why a Battery Horn Needs No Tank Space

Every "spare tire delete" train horn kit on the market solves the same problem: a compressor and a 2 to 5 gallon steel tank have to live somewhere under a pickup, and the spare tire well is the only cavity big enough. A battery-powered train horn has no tank, no compressor, and no air line, so the problem never comes up. Your spare stays exactly where the factory put it.

Why air-horn installs keep landing in the spare tire well

A conventional train horn is only as loud as the air behind it. That air comes from an onboard tank, and the tank is not small. The 2 gallon tank in a Conductor's Special kit from HornBlasters measures 17 inches long by 6 inches in diameter and weighs 10 pounds empty. Step up to the 5 gallon version and you are at 20.5 inches long, 9.5 inches in diameter, and 20 pounds. The 8 gallon tank runs 32.5 inches long and 32 pounds. A comparable 2 gallon Viair tank is listed at 19 inches by 6 inches by 7.5 inches and just under 12 pounds. Add a compressor, a pressure switch, a leader hose, and four trumpets from 12.75 to 19.5 inches long, and you need a flat, protected, roughly two-foot cavity under the truck.

On a modern pickup there is exactly one cavity like that: the spare tire well under the bed. That is why HornBlasters sells a bracket-based Spare Tire Delete kit that bolts the horns, tank, and compressor to a plate, then cranks the whole assembly up into place using the factory spare tire winch. Their published install estimate is 3 to 5 hours with basic tools. It assumes you will give up the spare or relocate it to the bed, a hitch carrier, or a rack.

What truck owners actually try when they want to keep the spare

The forums are full of people who want the sound but not the tradeoff. A thread on the Ford Tremor Forum titled "Train-horn without deleting the spare tire, recommendations?? For a 2023" lays out what keeping the spare on a Super Duty really involves. The suggestions from other owners:

• A single trumpet tucked in the gap behind the passenger-side running board, next to the frame rail.
• The compressor mounted behind the transfer case, in front of the fuel tank.
• Two 2.5 gallon tanks squeezed into that same space behind the transfer case, with one member warning it is exactly where an auxiliary fuel tank would go later.
• A 2 gallon tank and compressor bolted into the right front corner of the bed, giving up cargo space instead.
• A dual compressor mounted above the spare tire, with a 2.5 gallon tank behind the driver-side rear wheel, from a second Tremor thread on the same subject.

Every one of those works, and every one is a compromise. You either split the system into three or four pieces across the chassis, run air line between them, and drill brackets into the frame, or you give up the bed corner. One member described running half-inch DOT air line to the horn and air bags, with the compressor wired to a secondary battery in the engine bay. That is a weekend project, and it exists only because the tank has to go somewhere.

Why a battery horn has no tank to hide

A battery train horn generates its air on demand. Press the remote, the internal motor pushes air through the trumpets, release, and it stops. There is no reservoir to fill, no pressure switch, no drain valve, and no leader hose. The whole horn is one sealed unit that clips onto a cordless tool battery you already own.

Take the Extreme Series Train Horn for Milwaukee® 18v Battery as the reference. It runs on any Milwaukee® M18™ pack from 2.0Ah to 12.0Ah, puts out up to 150 dB through four powder-coated aluminum trumpets, and measures 14 by 6 by 12 inches at 4 pounds without the battery. That footprint is smaller than the 2 gallon tank alone, and it weighs less than half of it. There is nothing left over to put in the spare tire well because there is nothing left over at all.

Runtime is the question people ask next. On a 6Ah pack the rated figure is 500 or more short blasts, or about 200 sustained ones, per charge. The included remote reaches 160 feet, and the long-range remote extends that to 2,000 feet. Three volume settings let you turn it down in a campground and back up on the trail. Compare that with a 2 gallon air tank, which gives roughly a 3 to 4 second honk before the compressor has to refill it, a cycle that takes anywhere from 35 seconds to a minute and a half depending on which compressor the kit ships with.

Spare tire well vs battery horn, side by side

Item	Spare tire delete air kit	Battery train horn
Where the tank goes	Spare tire well, or split across frame rails and bed corner	No tank
Tank size and weight	2 gal: 17 in x 6 in, 10 lb. 5 gal: 20.5 in x 9.5 in, 20 lb	None
Whole-system footprint	Tank, compressor, wiring, air line, four trumpets up to 19.5 in	14 x 6 x 12 in, 4 lb plus battery
Spare tire	Removed or relocated	Untouched
Wiring	Compressor to battery, relay, pressure switch, horn button	None. Wireless remote
Published install time	3 to 5 hours (spare tire delete bracket)	Clip battery on, pair remote
Drilling	Frame or bed brackets, unless using the winch bracket	Optional. Strap, clamp, or magnet mounts work
Comes out of the truck	No	Yes. Same horn goes on the boat, UTV, or tailgate

The last row matters more than people expect. An air system is married to the vehicle it was installed in. A battery horn moves between the truck, the side-by-side, and the camp table in the time it takes to unclip it.

Why you want that spare to stay put

The spare tire under a pickup is not decorative. The National Highway Traffic Safety Administration tells drivers to check tire pressure at least once a month, when the tires are cold, and to include the spare in that check, which is a reminder of how much the agency expects you to rely on it. NHTSA's tire safety page lays out the rest of the routine.

Deleting the spare on a truck that tows, hunts, or works a ranch means carrying it somewhere else. An in-bed carrier eats bed floor, a hitch carrier blocks the receiver, and a bed rack is a separate purchase and install. All of that exists only to make room for a tank the battery horn does not have.

There is a quieter reason too. On a Super Duty the factory spare winch lowers through a hole under the license plate with the jack handle, and it seizes from rust if it sits untouched for years. Hanging an air kit bracket off that winch adds weight to a mechanism that already needs periodic grease.

Where a battery horn actually goes on a truck with the spare in place

Since you are not looking for a two-foot cavity, mounting gets simple. The usual choices on a pickup:

• Behind the cab in the bed. Strapped or clamped to the front bed wall or a headache rack, trumpets facing forward or to the side. The horn is out of the weather line of the tailgate and easy to reach for battery swaps.
• Bed toolbox. Inside a crossover box with the lid cracked for the blast, or with the horn stored inside and pulled out when you want it. Zero exterior footprint.
• Cab floor or rear seat. The horn rides inside, never sees rain, and comes out for the tailgate or the boat ramp.
• Under-bed frame rail pocket. The same running-board gap that Tremor owners use for a single trumpet fits a whole battery horn, with a strap or a small bracket. No air line to route because there is no air line.

For step-by-step mounting methods, our guide to mounting a portable train horn on a truck with no wiring covers strap, clamp, and bracket options. If you want the horn hidden entirely, ten stealth mounting spots for a battery-powered horn goes through the tucked-away locations that still throw sound.

One thing to remember on the frame-rail option: the horn is splash resistant, not waterproof. Under-bed spots that see direct wheel spray in winter are better served by a bed or cab mount. Trumpets pointed down or forward drain on their own.

Tier choice is about sound, not space. The Dual runs 130 dB with two trumpets at 14 by 6 by 9 inches and 3.4 pounds, the Quad reaches 140 dB with four, and the Extreme Series tops out at 150 dB. All three take the same battery and remote, and versions exist for DeWalt® 20V MAX™, Ryobi® ONE+™, Makita® LXT™, and most other tool-battery platforms. The F-150, Silverado, and Ram 1500 fit guide covers model-specific placement for the big three half-tons.

FAQ

Can I keep my spare tire and still get 150 dB?

Yes. The Extreme Series battery horn is rated at 150 dB and does not use a tank, so nothing competes with the spare for space. Sound level on a battery horn comes from the trumpets and the motor, not from stored air volume.

Can I install a spare tire delete air kit and just put the spare in the bed?

You can. An in-bed carrier holds the spare upright against the bed wall, and a hitch carrier hangs it off the receiver. Both cost money, both take up space you were using for something else, and the hitch option blocks towing. A battery horn skips the trade entirely.

Does a battery horn run out of air the way a small tank does?

No. A 2 gallon tank gives a few seconds of honk and then waits on the compressor. A battery horn makes air as long as you hold the button, and a 6Ah pack is rated for 500 or more short blasts before it needs a charge. The horn cuts off at 15 percent to protect the pack.

Is there any wiring at all?

None. The remote is a 433 MHz encrypted wireless unit, and the horn draws power directly from the tool battery clipped to it. There is no relay, no compressor lead, and no horn button to splice.