How heavy can an unbraked trailer be?

A loaded trailer without a braking system must not weigh more than 750 kg. GOV.UK's equipment page and DVSA's safety checks page, the second updated on 22 April 2024, both use that loaded figure. A trailer over 750 kg when loaded must have a working braking system. Brakes on a lighter trailer are optional, but any brakes present must work. You cannot disconnect them to duck a defect.

DVSA also says an unbraked loaded trailer should not weigh more than 50 per cent of the car's weight. That is guidance sitting next to the 750 kg legal line. A 900 kg car with a 500 kg loaded trailer is inside 750 kg and over half the car. The 750 kg rule is the one that creates the brake duty. The half-car figure is the one that stops a light car being shoved around by a legal-but-heavy box.

Yes. GOV.UK says you must use a breakaway cable or secondary coupling in case the trailer becomes detached. DVSA says that device engages the trailer's brakes if fitted, or stops the trailer. Check the cable is not worn, that there is enough slack so it does not apply the brakes on a turn, and that it will not drag. Follow the manufacturer on how to attach it. A secondary coupling is not optional because the trailer is under 750 kg.

Rule 98 says the trailer must be fitted with a secondary coupling device, such as a safety chain. That is a must. A missing cable on a garden trailer is the same legal gap as a missing cable on a caravan, even though the weights differ.

Weigh, or load with a clear margin. A bathroom scale under a jockey wheel is not a calibrated weighbridge, but it is better than a shrug. Check the coupling, the cable, the lights, the 1.6 mm tyre band, and the number plate matching the car. Mudguards must be fitted and secure, according to DVSA.

If brakes are fitted, they must work, even at 500 kg loaded. A seized drum on a 'small' trailer is a working-brakes failure. The MOT on the car will not catch it. The walk-round will.

Using an unbraked trailer over 750 kg loaded is using a trailer without the braking system GOV.UK requires. That can sit under the dangerous-condition figures: up to £2,500, a ban and 3 points. A prohibition can stop the outfit until the load comes off or a braked trailer is used. Insurance can take a view after a runaway.

A detached trailer with no secondary coupling is the version of this that ends up in the opposite carriageway. The cable is the cheap part. The court maximum is not.

A hire trailer still has to meet the 750 kg loaded rule. The hire desk sticker is not a waiver. Scotland and Wales use the same GB GOV.UK figures. Northern Ireland has its own construction and use rules. Use nidirect for an NI-specific brake threshold, and treat 750 kg on this page as the GB figure.

A trailer over 750 kg that goes abroad usually needs registration. That 750 kg line is a different 750 kg, about registration for other countries, not about GB brakes. Both can apply to the same trailer.

That 750 kg is the empty weight. It is loaded. That a trailer plated at 750 kg MAM can be loaded to 750 kg without brakes. MAM is a maximum. Loaded weight is the brake test. If you load it to 750 kg exactly, GOV.UK's wording is that a trailer must have a working brake system if it weighs over 750 kg loaded, so 750 kg exactly is not over. 751 kg is. Do not live on that 1 kg.

That a secondary coupling is only for caravans. Rule 98 says the trailer must have one. That half the car's weight replaces 750 kg. It sits beside it. The legal brake duty is 750 kg loaded.

GOV.UK's trailers, caravans and towing equipment page says the trailer must have a working brake system if it weighs over 750 kg when loaded, and that any brakes must be in good working order. DVSA's safety checks page says a loaded trailer with no braking system must not weigh over 750 kg and should not weigh more than 50 per cent of the car's weight. Both pages also require a breakaway cable or secondary coupling. Rule 98 says the trailer must be fitted with a secondary coupling device, such as a safety chain, and cites Construction and Use regulations.

The dangerous-condition tariff on the same GOV.UK equipment page is a fine of up to £2,500, a ban and 3 points. That is the published figure this page uses. A prohibition can stop the outfit until the load comes off or a braked trailer is used. Weigh the trailer as you will tow it, not as it sat empty in the yard.