From our own experience and knowledge of others its not safe to assume that "you will not be running at anything like maximum weight".
We didn't run particularly over full but until we weighed what we actually carried we made the same assumption and were wrong.
It's very easy to use up your payload without realising it.
However as far as the 85% guidance is concerned its just an unqualified guide number and other factors play a much more dominat part in unit stability than that particular ratio. Vehicle design, placement of the wheels, tyre type and pressure, lateral stiffness of rear suspension, allowable and used noseweight and wheel base to mention some. Then there is the caravan itself, weight distribution, axle location, aerodynamics and has it dynamic stability control.
In the OPs quoted case its 88.5% and if the other factors are correct this difference from 85% is meaninglessly small.
From our own experience and knowledge of others its not safe to assume that "you will not be running at anything like maximum weight". We didn't run particularly over full but until we weighed what we actually carried we made the same assumption and were wrong. It's very easy to use up your payload without realising it.
However as far as the 85% guidance is concerned its just an unqualified guide number and other factors play a much more dominat part in unit stability than that particular ratio. Vehicle design, placement of the wheels, tyre type and pressure, lateral stiffness of rear suspension, allowable and used noseweight and wheel base to mention some. Then there is the caravan itself, weight distribution, axle location, aerodynamics and has it dynamic stability control. In the OPs quoted case its 88.5% and if the other factors are correct this difference from 85% is meaninglessly small.
I think you're probably spot regarding using up the payload and not realising it but I'm sure my folks will have fun adding it all up and working out the best possible way to distribute the weight. As far as all the technical jargon that you quoted It's just that, I think sometimes It's nice not to get too complicated and use a portion of the good old fashioned common sense.
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We tow a 1482 kg MTPLM caravan with a 150 hp Zafira (about 90% match) and it tows fine.
In the past we had a Grand Scenic with a ratio of less than 80% and that was far less competent, so the oft quoted 85% ratio is not the be all and end all of towing stability.
Our first caravan was a 1179kg mtplm Ranger 470/4 and we had a Grand Scenic. We then changed the tow car to a Civic 2.2 CDTi (about 200kg lighter then the Scenic) and we also had the mtplm of the caravan increased to 1250kg as we had a mover and larger battery fitted. In all ways, this setup was more stable and a far more relaxing tow.
We have a Pagaent Bordeaux with MTPLM of 1300kg and tow with a Golf GT TDI , kerb weight 1500 ( according to weighbridge ) and 140bhp.
Towing at max weight gives us a figure of 86.6 % however as there are only two of us i reckon we are only running at 1200-1250 kg.
Car tows superbly , stable with lots of power , again only problem is on wet grass so will look at a mover this year.