Wolo 855-858 Express Pro Train Horn Kit Review (2026)

Methodology

This review aggregates publicly available information from manufacturer specifications, retailer listings, and verified user reviews. We do not perform hands-on testing. Last reviewed: November 12, 2026. Our primary source is Wolo Manufacturing’s current product page for the Model 855-858, cross-checked against an archived copy of Wolo’s previous product page, Wolo’s pages for the standalone 855 horn, the 858 air system, and the 855-860 Pro Plus combo, plus retailer listings at NAPA, RealTruck, and Auto Barn and a retailer sound demo on YouTube. Every source is listed at the end of this article.

Quick verdict

The Wolo 855-858 Express Pro earns a 3.8/5 from us. It takes the honestly rated, 128 dB, three-trumpet Wolo 855 Wolo Express horn and bundles it with Wolo’s 858 onboard air system — a 21-amp compressor and a 2.5-gallon metal tank — at a $273.99 list price that undercuts buying the two pieces separately by roughly $150. Wolo publishes an unusually complete spec sheet, right down to duty cycle and pressure-switch set points. What holds it back: ABS plastic trumpets, no published dB test distance, no warranty terms on Wolo’s own page, and patchy availability at the moment.

What it is

The 855-858 is a complete bolt-on train horn kit. Wolo pairs its Model 855 Wolo Express horn — three black trumpets molded from reinforced ABS plastic on a steel base — with its Model 858 high-pressure onboard air system. Everything needed to make air and blow the horn is in the box; you add wiring, a switch, and an afternoon of install time.

Wolo says it was the first company to design and sell ABS train horns, and the 855’s party trick is its universal flat rack: the trumpets sit side by side instead of in a stacked fan, so the assembly needs less mounting depth than most train horns. Per Wolo’s product description, the trumpets can also be separated from the base for installs with limited space — a useful option when the frame rail won’t take a 19-inch-long rack in one piece.

The target buyer is a pickup, SUV, or light-truck owner starting from zero onboard air who wants a deep, train-style chord without spending HornBlasters money. If you already run an air system, the horn-only 855 is the smarter buy.

On sound: the 855 horn is tuned to a low 308 / 337 / 366 Hz chord. A Northern Tool YouTube demo of the 855 horn shows the three notes blending into one deep blast rather than three distinct tones — closer to “train” than “semi.” Our chord and trumpet tuning guide explains why a tight, low chord sounds bigger than its decibel number suggests.

Specifications

All values below are Wolo’s published specifications unless noted.

Spec	Value
Sound output	128 dB at 90/110 PSI (test distance not disclosed)
Chord	308 / 337 / 366 Hz (low range)
Trumpets	3, reinforced ABS plastic, semi-gloss black
Base	Steel, painted enamel / black powder coat
Horn size	19 in. L × 18 in. W × 9.5 in. H
Horn valve	Built-in 12V electric solenoid, 300 mA
Compressor	12V, 21 A at peak, 2.55 CFM
Compressor duty cycle	33% at 100 PSI
Compressor type	Oil-less, gearless permanent-magnet motor, thermal protection, washable air filter
Compressor size	10.25 in. L × 3.5 in. W × 6.5 in. H
Tank	2.5 gallons, metal
Pressure switch	On 80 PSI / off 110 PSI (combo page)
Tank size	17.25 in. L × 6.5 in. W × 8.25 in. H
Tank with compressor mounted	17.25 in. L × 6.5 in. W × 15.5 in. H
Hoses	10 ft 1/4 in. O.D. high-pressure hose; 20 ft coiled filler hose
Fittings	Brass
Weight	40 lb (Wolo listing)
List price	$273.99 (Wolo direct, out of stock at review time)
Warranty	Not stated on Wolo’s page; NAPA lists 1 year

Rated output

128 dB @ 90/110 PSI

Chord

308 / 337 / 366 Hz

Air

21 A compressor + 2.5 gal tank

Duty cycle

33% @ 100 PSI

A note on the numbers. 128 dB is far below the “150 dB” claims common on budget train horn listings, and that counts in Wolo’s favor — our guide to advertised vs real-world decibels explains why realistic ratings in the high-120s often out-honk inflated ones. Wolo does state the test pressure, but not the measurement distance, so cross-brand comparisons stay approximate.

One small inconsistency is worth flagging: the 855-858 combo page lists the tank’s pressure switch at 80 PSI on / 110 PSI off, while Wolo’s standalone Model 858 page lists 80 on / 120 off. Check the gauge after install to see which switch you received.

What’s in the box

• Model 855 three-trumpet ABS horn on a detachable steel flat-rack base
• Built-in heavy-duty 12V electric solenoid valve (300 mA)
• 12V oil-less compressor with four rubber isolation bushings in the base plate
• Extended-length stainless steel high-pressure hose (compressor to tank)
• 2.5-gallon metal air tank with built-in pressure switch, pressure gauge, safety relief valve, and petcock water drain
• 10 ft of 1/4 in. O.D. flexible high-pressure hose (tank to horn)
• 20 ft coiled filler hose with brass fittings
• Brass air fittings and mounting hardware

Not included: a dash switch, relay, wire, or a mounting bracket specific to your vehicle. Wolo’s standalone 858 page lists a 25-amp in-line fuse with that air system, but the 855-858 combo page doesn’t list one, so plan to supply your own if it’s missing.

Pros

• Honest 128 dB rating with a published 90/110 PSI test pressure — no inflated marketing numbers
• Low 308/337/366 Hz chord gives a deeper voice than most compact air horn kits
• Complete kit at $273.99 list — about $150 less than Wolo’s prices for the 855 horn and 858 air system bought separately
• Very detailed published specs: duty cycle, CFM, amp draw, pressure-switch points, and dimensions for every component
• Flat-rack horn with detachable trumpets fits tight spaces better than fan-style clusters
• 2.5-gallon tank stores enough air for repeated full blasts at this price point

Cons

• Out of stock at Wolo direct and NAPA when we checked; other retail listings run about $350–$400
• dB test distance not disclosed
• ABS trumpets don’t match the tone or long-term durability of metal horns (editorial view)
• No warranty terms on Wolo’s own product page — only a retailer-stated 1-year warranty
• 33% duty cycle means the compressor needs rest after long refills
• Combo and standalone 858 pages disagree on the pressure-switch cut-out (110 vs 120 PSI)

Alternatives

• Wolo 855 Wolo Express (horn only) — the same horn without air at $159.99 list; the better buy if you already run onboard air. See our Wolo 855 Wolo Express review.
• Wolo 855-860 Express Pro Plus — the same horn with Wolo’s bigger 860 system (5-gallon tank, 3.5 CFM, 22 A at peak) for $298.99 list. It’s only $25 more and gives you twice the stored air, if you can find it in stock.
• Wolo Philly Express PRO 853-800 — a smaller, more compact Wolo kit for buyers who prioritize space over chord depth. See our Philly Express PRO 853-800 review.
• Wolo 850-858 Siberian Express Chrome PRO — the step-up in the same family: chrome trumpets, a 152 dB rating, and the same 858 air system at $389.99 list. See our 850-858 review.

All of Wolo’s train horn reviews are collected on our Wolo brand hub.

Install / compatibility notes

The 855-858 suits any 12-volt vehicle with room for three components: the 19 × 18 in. horn rack, the 17.25 in. tank, and the compressor. Wolo’s spec sheet also gives a 15.5 in. height for the tank with the compressor mounted on top, which is handy for frame-rail installs where you’d rather run one assembly than two. Wolo publishes separate installation PDFs for the horn and the onboard air system on the product page.

1. Plan the layout. Under-bed and frame-rail locations are typical on full-size pickups. Keep the compressor out of direct road spray and point the trumpet bells down or rearward so water drains. Our compressor mounting guide and horn mounting guide cover placement.
2. Wire the compressor properly. At 21 A peak, the compressor needs a relay and a fuse wired directly from the battery, with wire gauge to match. See our amp draw and wire gauge guide.
3. Wire the horn. The 855’s solenoid draws only 300 mA, so a simple switched 12V feed (or a relay off the factory horn circuit) is enough.
4. Plumb the air. The stainless line runs from the compressor to the tank, and the 10 ft of 1/4 in. hose runs from the tank to the horn. If your horn sits farther away, upgrade the line; our air line size guide explains the trade-offs.
5. Drain the tank. A metal tank collects condensation. Use the petcock drain regularly, especially in winter.

The duty cycle matters in real use. At 33% at 100 PSI, Wolo’s compressor is rated to run about one-third of the time, so refilling the 2.5-gallon tank after a string of long honks is the scenario where it will need to cool. For typical use — a few honks, then a refill — that isn’t a problem, but it’s worth understanding before you buy; our compressor duty cycle guide and air tank size guide walk through the math. Before wiring the horn to your daily-driver horn circuit, check your state’s rules in our horn law index.

Sources

• Wolo — Model 855-858 Wolo Express Pro product page — all kit specs (dB, PSI, Hz, materials, dimensions, solenoid, compressor amps/duty cycle/CFM, tank, pressure switch, hoses), 40 lb listed weight, $273.99 list price, out-of-stock status, product photos
• Wayback Machine — archived Wolo 855-858 product page (Nov 18, 2025) — cross-check of specs and full product description (detachable trumpets, rubber bushings, stainless line, included items, install PDFs)
• Wolo — Model 855 Wolo Express (horn only) product page — $159.99 horn-only price, recommended 840/858/860 air systems
• Wolo — Model 858 Tornado compressor & 2.5-gallon tank product page — $264.99 standalone price, 80/120 PSI pressure switch, included 25 A fuse, 150 PSI relief valve
• Wolo — Model 855-860 Express Pro Plus product page — $298.99 price, 5-gallon tank, 3.5 CFM, 22 A compressor for the alternatives comparison
• Wolo — Model 850-858 Siberian Express Chrome PRO product page — 152 dB rating, chrome trumpets, $389.99 list price for the alternatives comparison
• NAPA — Wolo Express Pro Train Horn 855-858 — $334.22 retail price, out-of-stock status, retailer-stated 1-year warranty
• RealTruck — Wolo Express Pro Truck Train Horn 855-858 — retail listing and price cross-check (~$349.99)
• Auto Barn — Wolo Express Pro Train Horn Kit — upper end of the retail price range (~$399.95)
• YouTube — Wolo Express Train Horn 3 Trumpets Model 855 (Northern Tool demo) — retailer sound demonstration of the 855 horn’s chord

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