Rear-mounted spare wheels—on a bar, a swing-out carrier or a wheel-carrier on the tailgate—are everywhere on Australian 4WDs and touring rigs. They free up cargo space and keep a second spare handy, but they sit right where your number plate, lights and rear overhang all have legal limits. This guide covers the rules that decide whether a rear-mounted spare wheel is legal, and the load maths people overlook. It’s the companion to the how-to in carrying a second spare on a 4WD legally.

Is a rear-mounted spare wheel legal in Australia?

Yes—provided it doesn’t compromise three things: your number plate, your rear lights, and your vehicle’s load limits. A spare wheel bolted to the back is treated much like any rear accessory (a bike rack or wheel carrier): the law doesn’t ban it, but it does insist the essentials behind it stay visible, lit and within weight. Get those right and you’re compliant in every state; get the plate or lights wrong and you’re an easy target for a defect notice.

Number plate: the 45-degree rule

This is where most rear-spare setups fall down. Across most Australian states your rear number plate must be:

• Visible within an arc of 45 degrees from each side, read from 20 metres away.
• Mounted between 300mm and 1300mm above the ground.
• Rigidly fixed, roughly vertical and parallel to the axle—not tilted or obscured.
• Lit by a working, colourless number plate light that illuminates the plate without projecting light rearward.

A spare wheel, jerry can or bike often makes it hard to find clear, visible space—which is exactly why relocation brackets and light bars exist. If the wheel blocks the plate or its light, relocate the plate to a compliant bracket. Rules vary a little by state (the NT uses reduced angles for lighter vehicles; SA and Tasmania focus on plain legibility at 20m), so check your state authority. See the detail in the number-plate discussion for multi-spare touring setups.

Tail-lights and indicators

The spare must not obscure your brake lights, indicators, reversing lights or reflectors. If the carrier sits over any of them, you’ll need a compliant auxiliary light bar wired to mirror the vehicle’s lights. Anything a following driver needs to see has to stay clearly visible from behind and the sides.

Weight: rear axle, GVM and overhang

A spare wheel and carrier can add 40–60kg or more, hung right at the back—the worst place for leverage. That weight counts against two ratings you must not exceed:

Limit	What it means	Why the rear spare matters
Rear axle rating	Max load the rear axle may carry	A rear-hung wheel loads it directly
GVM	Max total loaded vehicle mass	Carrier + wheel eats into payload
Rear overhang	How far load extends behind the rear axle	Swing-out carriers push weight rearward

As a general rule for light vehicles, rear overhang is limited to the lesser of about 60% of the wheelbase or a set distance—confirm the figure for your vehicle with your state authority, because the rules are prescriptive. If you’ve done a GVM upgrade, recheck your numbers, and make sure your tyres’ load rating still covers the heavier rear. Towing adds another layer—see tyre rules for towing.

Mounting and the spare itself

The carrier must be securely mounted so the wheel can’t work loose on corrugations—a common failure point on outback tracks. Use the rated fasteners, check them after the first few hundred kilometres, and don’t forget the practical stuff: keep the spare at the correct pressure, and if you run all-terrains, make sure your spare matches—see whether you need a different spare for all-terrain tyres. Because rules differ by state and a marginal setup can attract a defect, a quick check with your state road authority or an approved certifier is cheap insurance.

Which vehicles most need a rear carrier?

Rear carriers make most sense on touring 4WDs and utes that already run a full-size spare and want a second one for remote travel, or where a larger all-terrain spare no longer fits the original location after a lift or bigger tyres. Wagons like the LandCruiser and Patrol commonly use swing-out carriers on the rear bar; dual-cab utes more often carry the second spare in the tray or on a headboard rack. If you only ever drive sealed roads, a single under-body spare is usually enough—a rear carrier just adds weight and a compliance job you don’t need.

Frequently asked questions

Can a spare wheel legally cover my number plate?

No. If the wheel blocks the plate or its light, you must relocate the plate to a compliant bracket that keeps it visible within a 45° arc from 20m and properly lit.

Do I need engineering approval for a rear wheel carrier?

Often not for a bolt-on carrier within limits, but if it changes rear overhang significantly or your loaded weights approach GVM or axle ratings, check with your state authority or a certifier.

How much weight does a rear spare add?

A wheel plus carrier commonly adds 40–60kg at the rear. Because it hangs behind the axle, it eats into rear-axle capacity and payload faster than weight carried over the axle.

Does a rear spare affect towing?

It can, by adding rear weight and overhang that interact with tow-ball download and GCM. Recheck your combined weights if you tow.

Legal requirements vary by state and change over time—this is general information, not legal advice. Confirm the current rules with your state road authority or an approved vehicle certifier before fitting.

Sources: Club 4×4 – Is your number plate legal?; Transport Victoria – Overhang limits.