UK Towing Laws Explained: What’s Your Max Weight?

Getting your towing weights wrong isn’t just a safety risk—it’s illegal. For a first-time caravanner, the terminology (MTPLM, Kerbweight, train weight, 85% rule) can feel like learning a new language.

Here at Golden Castle, we believe the best way to enjoy your caravan is to tow it safely and legally. This guide cuts through the jargon and tells you exactly where to look and which numbers matter so you can match the perfect caravan to your car, with total confidence.

The Two Key Numbers You Must Know

Before you look at a single caravan, you need to understand two key weights: one for the car, and one for the caravan.

1. The Caravan’s Weight: MTPLM

This is the Maximum Technically Permissible Laden Mass.

The MTPLM is the heaviest the caravan is legally allowed to be when it’s fully loaded with water, gas, luggage, food, and accessories. It’s the number that matters when assessing if your car can tow it. You will find this figure on the caravan’s plate or in its manual.

2. The Car’s Weight: Kerbweight

The Kerbweight (or Mass in Running Order) is the vehicle’s weight when it’s empty but ready to drive (including a full tank of fuel, lubricants, and standard equipment).

The Kerbweight is the figure used in the popular stability guideline, the 85% Rule.

The Legal Limit: Where to Find Your Car’s Max Towing Capacity

While the 85% Rule governs stability, your car’s legal limit governs legality. You must not tow a caravan with an MTPLM higher than your car’s specified maximum towing limit.

You can find this maximum limit in two places:

A. Your V5C Registration Document

This document (the ‘logbook’) sometimes lists the “Maximum Mass to be Towed”. Look for a section listing maximum braked or unbraked mass.

B. The Car’s VIN Plate (or Chassis Plate)

This is usually found under the bonnet, on a door pillar, or stamped near the front windscreen. The plate shows four key numbers, typically listed in kilograms (kg):

• Vehicle Maximum Mass: The maximum weight of the car itself.
• Train Weight (GTW): The maximum combined weight of the car and the caravan (the whole outfit).
• Front Axle Max Load.
• Rear Axle Max Load.

To find your car’s maximum towing capacity, you must calculate it:

Maximum Towing Capacity = Train Weight minus Vehicle Maximum Mass

If your MTPLM exceeds the result of this calculation, you cannot legally tow that caravan with that specific car.

The Towing Guideline: The 85% Rule

The rule is a recommendation (not a law) that states:

Caravan MTPLM should be less than or equal to 85% of the Car’s Kerbweight

Why is this rule so popular?

It dictates stability. Keeping the caravan’s weight significantly less than the tow car’s weight drastically reduces the risk of the dreaded “caravan snake” or snaking motion, especially when braking, passing HGVs, or driving in strong winds.

• Under 85%: Recommended for all caravanners, especially first-timers. Excellent stability.
• 85% to 100%: Acceptable for experienced tow drivers, but requires greater care.
• Over 100%: Generally discouraged by safety bodies, as the outfit may become unstable and difficult to control in an emergency.

 UK Licence Rules: Do I Need a B+E Test Anymore?

The rules around towing licenses in the UK have changed significantly, making life simpler for most caravanners.

The Major Change (Dec 2021)

From December 2021, the government removed the need for the B+E towing test.

That means if you hold a standard Category B car licence (which covers most drivers), you can now tow a caravan or trailer — as long as the combined weight (car + caravan) doesn’t exceed 3,500kg.

In short:

👉 If you have a full car licence, you can tow — no extra test needed.

Key Takeaway for New UK Tow Drivers:

Most drivers in the UK can now tow a standard caravan without taking a specific test, provided the combination’s weight stays within the legal limits of the car and the license category (3,500 kg total).

If you are unsure, always check your driving licence information on the DVLA website.

Stay Legal: UK Towing Speed Limits

Once you have the right weights, you must adhere to different speed limits when towing a caravan in the UK. A vehicle towing a caravan is restricted to lower speeds.

Road Type	Car Speed Limit (Not Towing)	Towing Speed Limit
Motorways	70 mph	60 mph
Dual Carriageways	70 mph	60 mph
Single Carriageways	60 mph	50 mph
Built-up Areas	30 mph	30 mph

Important Note: You are also restricted to driving in the far left and middle lanes on a three-lane motorway; you must not use the outside lane.

Conclusion

Understanding your weights isn’t about complexity; it’s about preparation. By knowing your car’s legal maximum and following the 85% stability rule, you ensure that your holiday trips are safe, legal, and stress-free.

Need a quick way to keep all these essential weights, legal documents, and speeds handy for your first trip?

Frequently Asked Questions (FAQ)

Is the 85% rule a legal requirement in the UK?

No, the 85% rule is a guideline recommended by The Caravan and Motorhome Club and industry experts for safe, stable towing, especially for new drivers. The only legal requirement is that the caravan’s weight (MTPLM) must not exceed your car’s official maximum towing capacity.

What is the maximum width allowed for towing a caravan in the UK?

The maximum permitted width for a caravan in the UK is 2.55 metres. Most modern UK caravans are built to a maximum width of 2.44 metres.

What is the maximum length allowed for a car and caravan combination?

The maximum length for a caravan towed by a vehicle weighing up to 3,500 kg is 7 metres (excluding the tow bar). The overall combined length of the car and the caravan must not exceed 18 metres.