Towing Weight Limits Explained — What You're Actually Allowed to Tow

Exceeding your towing limit isn't just dangerous — it's illegal and invalidates your insurance. Here's how to calculate exactly what your car can tow.

Towing limits are set in law and by your vehicle's manufacturer. Exceeding them can cause loss of control, void your insurance, and result in a serious fine.

The Key Numbers

Kerbweight — the weight of the vehicle with a full tank of fuel and standard equipment, but no passengers or cargo. This is the base figure everything else is calculated from.

Maximum Authorised Mass (MAM) — the maximum the vehicle is legally allowed to weigh when fully loaded with passengers, cargo and fuel.

Gross Train Weight (GTW) — the maximum combined weight of the towing vehicle (at MAM) and the trailer (at MAM). Your vehicle's GTW is specified by the manufacturer and cannot be exceeded.

Towing capacity — the maximum weight of the trailer. Found in your owner's manual or on the manufacturer's website.

The 85% Rule

While not a legal requirement, the widely followed rule of thumb is that a loaded trailer should not exceed 85% of the towing vehicle's kerbweight for safe, controllable towing — especially for inexperienced towers. At 100%, the trailer can begin to control the vehicle rather than the other way around.

Where to Find Your Figures

Owner's manual

Manufacturer's website (enter your VIN or registration)

The V5C registration document

A plate on the towbar itself (which lists the towbar's specific rated limit — sometimes lower than the vehicle's rated limit)

What Happens If You Exceed the Limit

Your insurance is invalidated for any accident

You could face a prohibition notice stopping you from driving until the load is reduced

Fines of up to £300 and points on your licence

In a serious accident, you could face criminal charges

If your towing setup breaks down near Newport, Cardiff, Bristol or Bath, Fred's Towing Services can recover both vehicle and trailer. Call 01633 982028.