The weights that decide what your car can pull
What a car can pull comes down entirely to a handful of plated weights, not engine size and not how planted the car looks doing it. Kerb weight is the car alone: fuelled, fluids topped up, ready to drive, but with nobody and nothing else aboard. Maximum authorised mass, usually shortened to MAM and sometimes printed as GVW, caps how heavy the car itself can get once driver, passengers and luggage are aboard, before any trailer joins the equation. A caravan or trailer carries an equivalent ceiling of its own, commonly labelled MTPLM, its own maximum permitted weight when packed for a trip.
Gross train weight (GTW) covers the whole outfit at once, car and trailer together, and it is nearly always lower than MAM and MTPLM simply added up, because towing loads the car's chassis, brakes and cooling harder than driving solo ever does. Towball or nose weight is the separate, smaller figure: the downward push the trailer's coupling presses onto the car's towball, capped independently of every other number on the plate.
Reading your own car's figures
None of the numbers above are guesswork for a specific car: they live on the VIN plate (riveted into the engine bay or a door shut), in the handbook, and on the V5C, which records MAM under the heading "revenue weight". The handbook usually states towing capacity as one clean figure, but the VIN plate carries the raw weights an examiner would check, typically stamped as four lines in kilograms.
A generic plate might read: line one, 2000, the car's own solo limit (MAM); line two, 3500, the combined limit for car and trailer together (GTW); lines three and four, individual axle limits, shown here only for illustration and not something this worked example needs. Line two minus line one gives the maximum braked trailer the car is rated to pull: 3500 minus 2000 leaves 1500 kilograms. Manufacturers order the lines differently, so treat any generic layout as a starting point and cross-check the actual figures against the handbook before trusting them.
Once those figures are off your own plate, our towing and payload checker takes them together with your trailer's real weight and works out spare payload, spare towing capacity, gross train weight headroom and the stability guideline below, all in one pass, rather than working each sum out separately.
The 85 percent guideline
Sitting alongside the plated numbers is a piece of industry guidance rather than a legal limit: a loaded caravan is best kept to around 85 percent of the towing car's kerb weight, tightening further for anyone new to towing, and rarely pushed past 100 percent. The reasoning is stability rather than strength. A heavier caravan behind a lighter car has proportionally more sway over the outfit if the ride gets unsettled at speed, so a lower ratio leaves the car doing more of the work of staying planted.
Noseweight, the number people forget
The download the coupling presses onto the towball typically works out around 5 to 7 percent of the trailer's actual weight, though it shifts with how the load sits inside. That figure has to stay under the car's own noseweight limit, a separate number from anything on the VIN plate's main lines and usually found in the handbook or on a small plate near the towbar. Run too low and a trailer can feel loose behind the car at speed; run too high and the extra weight loads the car's rear axle instead of staying on the trailer's own wheels. A bathroom scale placed under the jockey wheel gives a rough reading before setting off.
Trailers without their own brakes
Smaller trailers with no brakes of their own follow a different rule: the limit is 750 kilograms, or half the towing car's kerb weight, whichever comes out lower. Most family cars have a kerb weight comfortably above 1500 kilograms, so 750 kilograms ends up being the figure that applies in practice for the majority of them, but it is worth working out the half-kerb-weight number directly on a lighter car rather than assuming.
Licence rules
What a driving licence permits when towing changed for people passing their test from the end of 2021 onward, and the combination weight a given licence now allows depends on the test date and the categories actually held on it. A summary written today can be stale within months, so check the current DVLA guidance against your own licence directly: it is the one source that reflects your specific entitlement.
Can I tow at motorway speed?
It depends on the road: towing drops the usual maximum to 50mph on single carriageways, and to 60mph on dual carriageways and motorways, even where a car on its own could otherwise go faster. Wherever a lower limit is signed for that specific road, the signed figure is the one that applies.
Do I need towing mirrors?
If the caravan or trailer is wider than the car, or wide enough that the car's standard mirrors cannot see far enough down both sides past it, extended towing mirrors are a legal requirement rather than an optional extra. Whether a specific trailer crosses that line depends on its width measured against what the car's own mirrors already cover, so it is worth checking before a long trip rather than assuming standard mirrors are enough.