Steve, I know this is the second time that this debate has appeared. You probably don't remember from the first one, I supported your idea, just like I support Keith's idea. I too would like to know how a car would handle at max load, just because two cars look similar and have similar specs, it does not mean that they will handle the same. Only a few years ago PC were testing cars that were found wanting in the towing area, although perfectly capable while solo. I find this information interesting, and worthy of note.
I also know your past with 4x4s, you have mentioned it in the forum, but the subject was creeping in again, I could see this thread being deleted too. I have no wish for a 4x4 debate, I have had enough of them, as far as I am concerned, you drive what you want, so let me drive what I want.
As for the 85% rule, you are correct, loading is just as important. However it is difficult to police loading generally, it's down to human failure where that is concerned. However the 85% rule can be flagged up when the professional bodies come into contact with a caravanner. The reputable companies already do so, giving advice on what you can tow and what your better of towing
If your driver had been towing at 85% maybe he could have avoided the accident, I say maybe, because I was not there and didn't investigate the event.
You may well be ROSPA trained and part of the advanced drivers club, (I didn't realise they did a course that used caravans) but I am not, and nor are the vast majority that tow a caravan. You may feel safe towing at 100%, but would you trust someone who isn't as well trained to do the same? That's why it is a good rule, it helps overcome some of the inadequacies of fellow caravanners, myself included.
To be truthful, I don't like the 85% rule, no; I would much prefer the 85% law.
On nearly every occasion that I tow, my wife is sat besides me, and that alone is enough for me to want to make that journey as safe as possible. If it means buying a heavy car, checking the loading and using my noseweight gauge every time, then that is what I'll do. I can have fun and take risks when I am on my own, but I prefer to be sensible when someone else is involved.
Having said that, not everyone gets to choose their towcar, that is why the information you and Keith seek is important.
Now, go on, you were saying?