Tolerances in Towing limits

[Javert]

As a newcomer to all this, can I ask how much tolerance is generally built in to the capacities quoted like nose weight limit on the car and so on?

I've seen posts where people were towing with a higher nose weight than the car limit as they said they could not get it lower or suchlike.

I'm guessing that there must be some tolerances built in there because I assume the true moment to moment nose weight would change e.g. if you are braking/accelerating/uphill/downhill?

e.g. if the limit is 80Kg but my actual is 83 or 85 or suchlike, is this extremely dangerous or just may not drive very well?

 

[Woodentop]

This is all done on a level surface.
The towing limit is the lowest of the towcar limit, the towbar load capability or the noseweight of your caravan.
Guidelines are that the towbar capability should be 5-7½% of the MTPLM of the caravan - most of those specified for you vehicle will exceed this range by a margin. The towcar chassis limit is calculated from the figures on the vehicle plate - on most cars of Euro manufacture this will be near the bottom of the B-pillar (between the front and rear doors) on the UK nearside. Of the two top numbers subtract the smaller number from the larger number will give you the maximum load the car chassis can tug. If there is only one top number the vehicle is not homologated for towing. (The numbers alongside 1 and 2 are the front and rear axle maximum loads respectively and can be ignored.)

 

[Lutz]

As far as the law is concerned, there are no tolerances and certainly none that you can rely on. It's always up to the officer concerned whether a degree of discretion is exercised.
That said, exceeding the noseweight limit is not an offence in itself. It only documents the vehicle manufacturer's limit to which he accepts product liability. In other words, you're on your own if the noseweight is greater than the limit and that has resulted in material failure. However, chances are that if you exceed the noseweight limit, you may also be exceeding the car's rear axle load limit, and that is a punishable offence.

 

[Javert]

As far as the law is concerned, there are no tolerances and certainly none that you can rely on. It's always up to the officer concerned whether a degree of discretion is exercised.
That said, exceeding the noseweight limit is not an offence in itself. It only documents the vehicle manufacturer's limit to which he accepts product liability. In other words, you're on your own if the noseweight is greater than the limit and that has resulted in material failure. However, chances are that if you exceed the noseweight limit, you may also be exceeding the car's rear axle load limit, and that is a punishable offence.

Thanks - well I am not thinking about a large difference - I was also thinking about an error of maybe 1 or 2kg which presumably could happen just by differences in scales or there being a very slight gradient where you do the measuring. Similar to car speedometer where everyone knows that there is a tolerance in the speed limits due to not every speedometer reads the exact same.

 

[Lutz]

I doubt whether the scales that the powers-that-be use are that accurate that they would indisputably prove a 1 or 2kg transgression. However, if you are able to set your noseweight 2 kg above the limit, it's just as possible to set it 2kg below the limit and that would avoid any possible conflict.

 

[Hutch]

Nose weights are a big can of worms. Most people agree that Measuring the nose weight at the tow hitch with the hitch at the same height as when hitched up. Almost impossible to do depending on what your carrying in the car.
Bathroom scales blocked to take the weight of the hitch is the easiest. But how accurate are the scales. I tend to give them a +/- of 5 kg for my measured nose weight. I personally would not worry about running at 85 kg when your cars hitch is rated at 80,kg.

 

[otherclive]

I generally used to try for a noseweight 3-5 kg below the maximum. One way to calibrate your bathroom scales is to fill a large suitcase to 22.5kg as weighed on your scales, then book a TUI flight with 23kg limit and you can get a confirmatory check at your local airport.

 

[Lutz]

I generally used to try for a noseweight 3-5 kg below the maximum. One way to calibrate your bathroom scales is to fill a large suitcase to 22.5kg then book a TUI flight with 23kg limit and you can get a confirmatory check at your local airport.

I doubt whether the scales at an airport are any more accurate.

 

[ProfJohnL]

When ever you are given a "limit" that is what it says it is the" limit", Limits do not have any tolerance. there is no more to be had. That is certainly the case for the axle loads and the Gross and Train weights.

It is up to the driver to check their vehicle does not exceed any limit. If you have a measuring system that has +/- value or % error, you must assume the measuring device is under reading, and set your weight or load target to allow for the under read.

Some limits are legally enforced, and some are there as Lutz says to to set the liability of the manufacture for warranty claims. Few limits are made without good reason, so do not assume that any excess is a safe or sensible practice.