What Is a Tow Bar?
A tow bar (also called a trailer hitch) is a structural fitting bolted to the chassis or sub-frame at the rear of a vehicle that allows it to tow a trailer, caravan, boat, horse float, or car transporter. In New Zealand, tow bars are regulated under the Land Transport Rule: Vehicle Standards Compliance 2002 and must be fitted correctly to be legal and safe.
Most NZ tow bars use a 50 mm ball coupling (the standard ball diameter for most light trailers and caravans). Heavy-duty applications may use a pin-type coupling or a DO35/DO35-Pro coupling for farm trailers and horse floats.
Types of Tow Bar
1. Fixed Ball Tow Bar
The most common type in NZ. The ball is permanently attached to a fixed towball mount. It's simple, strong, and the most affordable option. Downside: the ball and mount protrude at all times, which can be a hazard in car parks and reduces rear approach angle off-road.
2. Detachable Tow Bar
The ball and neck assembly can be removed when not in use — typically by pulling a lever and lifting out the neck. Popular on SUVs and cars where aesthetics and rear-sensor performance matter. More expensive but preferred for daily-driven vehicles.
3. Retractable (Swivel) Tow Bar
The ball neck swings away or retracts into the bumper fascia when not in use. Premium option — common on European vehicles. Expensive to fit aftermarket.
4. A-Frame / Gooseneck
Used on trucks and heavy transport — not relevant for most NZ passenger vehicles.
Tow Bar Ratings: What They Mean
Every tow bar has two key ratings:
- Gross Trailer Mass (GTM) or Maximum Trailer Mass (MTM): The maximum weight of the trailer the bar can handle.
- Towball Download (TBD) or Vertical Load: The maximum downward force the towball can bear (typically 100–150 kg for light bars, up to 350 kg for heavy-duty).
Your vehicle also has its own towing capacity set by the manufacturer — the tow bar rating cannot exceed this figure. Overloading a tow bar or exceeding the vehicle's tow rating is illegal and dangerous. Check your vehicle's towing capacity in the owner's manual or via the NZTA vehicle information portal.
Wiring: What You Need
New Zealand trailers use 7-pin flat connectors (most common) or 7-pin round connectors. Your tow bar installation will typically include:
- 7-pin flat socket for lights (brake, indicator, tail, reverse light where fitted).
- Some trailers also require a 12V auxiliary socket for electric brakes or caravan power.
If your trailer has electric brakes (required for trailers over 2,000 kg in NZ), you will also need a brake controller fitted inside the vehicle. This is an NZTA requirement.
WoF Requirements for Tow Bars
A tow bar must:
- Be securely bolted to the vehicle — no movement or cracks in the mounting points.
- Not have a damaged or excessively worn towball (ball wear is checked; a badly worn ball can detach a trailer).
- Have functional trailer lights wired correctly (tested as part of the WoF trailer lighting check if a trailer is attached at the time of inspection, though the socket wiring itself is seldom inspected with the car alone).
A cracked, bent, or loose tow bar will fail a WoF.
NZ Costs
| Service | Typical NZ Cost |
|---|---|
| Basic fixed-ball tow bar supply and fit | $500–$900 |
| Detachable tow bar supply and fit | $900–$1,500 |
| Wiring harness (7-pin flat, plug and play) | Included or $100–$200 extra |
| Brake controller (electric trailer brakes) | $250–$600 supply and fit |
| Towball replacement only | $60–$150 |
Prices vary by vehicle — utes like the Toyota Hilux have simple bolt-on options; low-slung hatchbacks may require custom fitting.
When to See a Mechanic
- Before purchasing a tow bar — have a mechanic verify your vehicle's tow rating and recommended bar type.
- Tow bar is loose, cracked, or corroded — repair or replacement before next use.
- Trailer lights are not functioning — wiring fault needs diagnosing.
- Adding a heavy trailer — confirm your vehicle's braking system is adequate.