Before You Buy: 7 Towing Numbers to Check

Introduction

Before you commit to a tow vehicle or caravan, there are seven weight figures that tell you whether the combination will work. Looking at towing capacity alone is the most common — and most expensive — mistake Australian buyers make.

This guide lists each number, where to find it, and why both the published rating and your actual loaded weight matter. None of these figures is difficult to find, but they are rarely checked together before purchase.

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1. Towing Capacity (Braked Tow Rating)

**What it is:** The maximum trailer weight your vehicle is rated to tow when the trailer has its own brakes fitted.

**Where to find it:** The vehicle specification sheet, owner's manual, or the manufacturer's towing guide. It may differ between transmission variants, body styles or model years within the same vehicle line.

**Why both figures matter:** The published tow rating is a maximum ceiling determined under controlled conditions with a standard, unmodified vehicle. Once you add accessories, passengers and cargo to the vehicle, the practical towing capacity may be lower — constrained by payload, GCM or towball download limits (see below).

**What to check:**

• Confirm the braked tow rating for the exact variant, transmission and year you are buying
• Note whether the rating differs between manual and automatic variants
• Understand that tow rating is a ceiling, not a target

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2. GVM (Gross Vehicle Mass)

**What it is:** The maximum legal total weight of your vehicle when fully loaded — including the vehicle itself, all passengers, fuel, water, accessories, cargo and towball mass from the trailer.

**Where to find it:** The compliance plate (usually in the engine bay or driver's door jamb), the registration document, or the owner's manual specifications section.

**Why both figures matter:** GVM is the permitted maximum loaded vehicle mass, not the weight of a standard vehicle. Net accessories, passengers and gear change actual mass. Measure the fully loaded vehicle with an appropriate weighbridge or calibrated axle/wheel scales, then compare actual mass and each axle with the exact applicable limits.

**What to check:**

• Locate the GVM on the compliance plate
• Calculate payload: GVM minus tare (kerb) weight
• Understand that towball mass from the trailer counts against GVM

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3. GCM (Gross Combination Mass)

**What it is:** The maximum legal combined weight of your tow vehicle and trailer when coupled together.

**Where to find it:** The owner's manual, manufacturer's towing guide, or sometimes the compliance plate. Not all vehicles publish a GCM — if it is not stated, check with the manufacturer directly.

**Why both figures matter:** GCM is often the limit that catches buyers by surprise. A vehicle rated to tow 3,500kg with a GVM of 3,300kg does not automatically have a 6,800kg GCM. The GCM is commonly lower than the sum of GVM and tow rating, meaning a fully loaded vehicle may not be able to tow a fully loaded trailer to its maximum ATM without exceeding GCM.

**What to check:**

• Find the GCM for the exact vehicle variant
• Check: loaded vehicle weight plus loaded trailer weight must not exceed GCM
• Understand that a GVM upgrade does not automatically increase GCM or braked towing capacity

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4. Towball Download Limit

**What it is:** The maximum downward force the vehicle's tow bar is rated to accept from the trailer. This is separate from the overall tow rating.

**Where to find it:** The tow bar compliance plate (if aftermarket), the vehicle owner's manual, or the manufacturer's towing guide. The tow bar and the vehicle may have different limits — the lower of the two applies.

**Why both figures matter:** Some vehicles are rated to tow 3,500kg but only accept a limited towball download. A heavy caravan with a high towball mass could exceed this limit before the tow rating itself becomes relevant. The towball download limit is often lower than buyers expect.

**What to check:**

• Find the vehicle's towball download limit
• Find the tow bar's rated download (if aftermarket)
• Use the lower of the two limits
• Obtain the actual loaded coupling measurement for the intended setup; do not infer it from ATM

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5. Payload

**What it is:** Manufacturer payload is based on the specified mass definition. For your measured setup, remaining GVM capacity = GVM rating minus actual vehicle mass. Record fuel and equipment inclusions; tare and kerb are not interchangeable.

**Where to find it:** Calculate it yourself from GVM and tare weight. The tare weight is on the compliance plate or registration documents.

**Why both figures matter:** Published payload figures are based on the base model with standard specification. Your actual vehicle — with dealer-fitted options, a tow bar, side steps or other accessories — may be heavier than the brochure tare. This means your real payload is lower than the published figure from day one.

The vehicle mass budget must include passengers, fuel, water, accessories, cargo and coupling load once. Fuel or equipment already included in the starting mass must not be added again.

**What to check:**

• Calculate payload: GVM minus actual tare weight (not the brochure figure)
• List all planned accessories with actual or conservative weight estimates
• Add passenger weight (approximately 80kg per adult as a starting estimate)
• Add measured loaded towball download only if absent from the vehicle starting mass
• Add only fuel and water absent from the starting mass; record the mass basis
• Compare the total to available payload — before purchasing, not after

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6. Front and Rear Axle Limits

**What they are:** Separate weight ratings for each axle, operating independently of the overall GVM. You can be within GVM but still exceed an individual axle rating.

**Where to find them:** The compliance plate (usually in the engine bay or door jamb) and the owner's manual specifications section.

**Why both figures matter:** The rear axle is typically the first limit reached in a touring setup with a canopy, drawers, long-range tank and towball mass — all of which load the rear of the vehicle. The front axle is affected by bullbars, winches and dual batteries mounted up front.

Axle ratings are set by the manufacturer. A GVM upgrade does not automatically increase axle load limits, GCM or braked towing capacity. Any changes to axle ratings require specific engineering approval and depend on the vehicle, approved kit and registration jurisdiction.

**What to check:**

• Locate front and rear axle ratings on the compliance plate
• List rear-loaded items: canopy, drawers, long-range tank, towball mass, rear passengers, cargo
• List front-loaded items: bullbar, winch, dual battery, driver and front passenger
• Check whether rear-loaded items are approaching the rear axle rating

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7. Caravan ATM and GTM

**What they are:**

**Where to find them:** The caravan's compliance plate, usually on the drawbar or near the door.

**Why both figures matter:** ATM tells you the maximum the caravan can weigh when fully loaded. GTM tells you the maximum weight on the caravan's axles. ATM and GTM are separate maximum ratings. Their difference does not establish actual towball download. For the same measured loading condition without hitch redistribution, actual trailer total mass minus actual trailer axle mass gives coupling load.

Compare the intended actual loaded trailer mass with the vehicle and equipment limits and manufacturer conditions. Compare measured coupling download with the applicable download limits. ATM minus GTM does not establish today's coupling load.

**What to check:**

• Find the caravan's ATM and GTM on the compliance plate
• Check: ATM must not exceed the vehicle's tow rating
• Measure loaded coupling download; plated ATM/GTM are maximum ratings
• Check: towball mass must not exceed the vehicle's towball download limit

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Why Published Figures and Actual Loaded Weights Both Matter

Published specification figures are determined under controlled conditions with a standard vehicle. They represent the maximum legal limits — not a guarantee that your specific setup will reach those limits.

Your actual loaded weight depends on:

• The specific variant and options fitted to your vehicle
• The accessories you install
• The number and weight of passengers
• How much fuel, water and cargo you carry
• The actual towball mass of your loaded caravan

Confirm actual weights by measuring the fully loaded vehicle and caravan with an appropriate weighbridge or calibrated scales. Manufacturer documents, plates and applicable engineering approvals establish permitted limits; measurement establishes the actual loads to compare with those limits.

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Quick Reference: Where to Find Each Number

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