Hello again, alibabaxx
That is good news, it means that theoretically you could tow a trailer that weighs 1400kg whether the car is fully loaded or not.
Really the only reason you are trying to establish the cars kerbweight is to calculate the towing ratio then?
I'll assume that is your reason, and as such we need to get this 85% into perspective. It is only guidance! it has no legal implications, and it has no guarantees of making a good match or safe match, so a few % over is not going to be a deal breaker. Regardless of what the 'guidance may suggest, you must never exceed any maximum limits set by the tow vehicle manufacturer, as they do have legal implications.
Good towing is not achieved simply by getting a particular towing ratio, whether it 85% or any other figure. It's about getting a combination of factors into a sensible proportions. Other things such as ensuring both the tow vehicle and the trailer are properly maintained, using sensible loading methods to trim a sensible tow hitch nose load, good driving habits, taking proper actions in accordance to road and weather conditions. All these points are probably more important than the 'towing ratio'
The towing ratio is precise but anything but accurate (which is why I personally dislike such a prescriptive quoted value) The way its calculated represents the absolute worst possible case of the heaviest a caravan can be caravan towed by a car in it lightest possible configuration, a set of conditions that no one actually tows with so in reality the real 'ratio' will always be actually better than the calculated value.
Now the quoted kerb-weights you have are not exact, they are the manufacturers estimate and represent the range of weights they would expect allowing for manufacturing tolerances AND it may represent range for a number of models. You will be better using the MIS which is a measured weight of your vehicle, and its one of the figure the authorities will use if they query any vehicle loading concerns.
The most important thing is to ensure you do not exceed the vehicles maximum permitted weight limits, whist endeavouring to keep the trailer as light as possible.