This thread is unintentionally doing what I have complained about...
Obsessing about the importance of following a notional weight ratio, and failing to bring some of the other potentially more important aspects of setting up an outfit to the party.
Nose load,
Vehicle condition
Driving habits
Weights are not unimportant, after all there are some legal limits that must be observed, and whilst the 85% is only guidance, it is not without some merit. It at least alludes to the principal of keeping the mass of any trailer as minimal as possible.
However harking back to an earlier post
Parksy said:
camel said:
Prof,
It was not a criticism but reflecting on what you have been saying in many posts about the 85% towing limit which I think was plucked out the air years ago,
I've beaten the Prof to it :cheer: by pointing out that the 85% figure is not a limit, it's an advisory figure but it wasn't simply plucked out of the air as you suggest.
The figure was originally arrived at because some years ago the CC (now C&MC) worked with Bath university to recommend a safe towing ratio between car and caravan.
Car design has changed considerably since the figure was first recommended, but the consensus of informed opinion suggests that as a starting point for those new to towing, the 85% recommendation, along with correct caravan maintenance and loading procedures and good driving techniques, is still considered to be a safe towing ratio.
I'm quite surprised Parksy at your comment. I'm not sure where you have got your information from.
Despite having made extensive enquiries of the clubs, and a number of industry insiders over the years, None of my contacts could throw any formal light on the process used to derive the guidance except it was a committee decision. I could not establish the names or anything about who might have been on the committee.
It has also been equally frustrating to find that no one can point to the method or evidence used to come to any conclusions, so it certainly gives the impression the 85% advice was not based on scientific evidence.
Although I am critical of the curtain of silence the industry has drawn around the source of the advice, I am pretty certain the advice was produced in good faith, and based on the information available at at the time. which compared to today was not very extensive.
Parksy unless you have come into possession of some new information, I have never found any evidence that any University was involved in producing the industry guidance. The University of Bath (to give it it's correct name) was only founded in 1966, so I suspect it wasn't even established when the guidance was issued.
The University did collaborate with Bailey caravans to look at the towing characteristics of a Bailey caravan. It was part of that research which produced the oft refereed to model that demonstrates the effect of yaw inertia. The result of that study was limited to describing the characteristics of one particular car and caravan, and could not be used to as evidence of a general case for all possible combinations.
At no time has the industry formally linked the 85% guidance with any guarantee of safety, or legality, that has evolved with the numerous times the guidance has been misquoted.
I believe informed opinion is actually divided about the efficacy of the advice, but there is a consensus that until a better more reliable method has been formulated, flawed as it is the 85% guidance is a lot better than nothing, and is a starting point.