Weights and towing limits

By the end of this topic you can

• You can explain DGVW, DGCW and unladen weight.
• You can find your car's braked and unbraked towing limits.
• You can tell a light trailer from a heavy one.
• You can explain what nose weight is and why it must be within limits.
• You can check whether a loaded trailer is within every relevant limit.

What you need to know and understand

• DGVW (design gross vehicle weight) is the most a vehicle or trailer may weigh fully loaded, as set by the maker.
• DGCW (design gross combination weight) is the most the car and trailer together may weigh, as set by the car maker.
• A light trailer has a DGVW of 3,500 kg or less; anything heavier is a heavy trailer.
• Light trailers are type O1 (up to 750 kg) or O2 (over 750 kg up to 3,500 kg).
• A car's unbraked towing limit only applies to trailers up to 750 kg; heavier trailers must have brakes.
• Exceeding your vehicle's towing capacity is breaking the law.
• Nose weight is the downward force the trailer coupling puts on the tow ball; the car and tow bar makers set a maximum.

The weights on the plates

Your licence entitlement is worked out from the plated maximums. Your car's towing capacity is a separate limit you must also respect.

• DGVW of the trailer: on the statutory plate fixed to the trailer. All new light trailers sold since 29 October 2012 must be plated.
• Unladen weight: the trailer or car with no load. Ask the maker or use a local authority weighbridge.
• Towing capacity: the most your car can pull, braked and unbraked. Find it in the owner's manual or ask the maker or dealer.
• DGCW: the maximum for car and trailer together, set by the car maker.

Working out a safe load

1. Find your car's braked and unbraked towing capacity and its maximum nose weight.
2. Check the trailer's plated DGVW. A trailer over 750 kg must have a service brake, a handbrake and a breakaway brake.
3. Take the trailer's unladen weight away from its DGVW to see how much load it can legally carry.
4. Make sure the loaded trailer does not exceed your car's towing capacity or the trailer's DGVW.
5. Load so the nose weight is within the limit set in the handbook: heavy items low and over the axle, slightly forward rather than at the back.
6. If in doubt, weigh the loaded trailer at a weighbridge.

Why nose weight matters

Too little nose weight, usually from loading at the back, makes a trailer lift the rear of the car and is a common cause of snaking. Too much presses down on the tow ball, overloads the car's rear axle and lightens the front wheels, so steering and braking suffer.

Your car handbook and the tow bar plate give the maximum. A simple nose weight gauge under the coupling lets you check it at home.

Common mistakes

• Using the braked towing limit for an unbraked trailer. Unbraked limits are much lower and only go to 750 kg.
• Ignoring the car's towing capacity because the licence allows the combination. Both limits apply.
• Loading heavy items at the very back. It cuts nose weight and makes the trailer unstable.
• Guessing the load weight. Use a weighbridge when you are close to a limit.
• Forgetting that people and luggage in the car count towards the combination weight.

Test yourself: Weights and towing limits

Answer each question, then read the explanation. Questions come in a random order each time.