“Combined” Weighbridge weight correct or wrong?

Page 2 - Passionate about caravans & motorhome? Join our community to share that passion with a global audience!
Jul 18, 2017
13,169
3,758
40,935
Visit site
Makes me wonder what a traffic officer would use to determine that a caravan is exceeding its MTPLM and to bring about a successful prosecution as they cannot use the sticker on the body work? I think the legislation refers to "axle" weights?
 
Aug 5, 2023
424
159
235
Visit site
Makes me wonder what a traffic officer would use to determine that a caravan is exceeding its MTPLM and to bring about a successful prosecution as they cannot use the sticker on the body work? I think the legislation refers to "axle" weights?
You would think it would be the axle weight wouldn’t you, I mean that’s where the weight is pressing down. Not about where the weight is.

Must be the same for trailers the?
 
Mar 14, 2005
9,837
724
30,935
lutzschelisch.wix.com
Makes me wonder what a traffic officer would use to determine that a caravan is exceeding its MTPLM and to bring about a successful prosecution as they cannot use the sticker on the body work? I think the legislation refers to "axle" weights?

Legislation refers to both axle weight and total weight. Gross train weight, a legal limit, is the sum of all axle weights of the combination, i.e. those of the car and of the caravan. Gross vehicle weight of the car, again a legal limit, is the sum of its front and rear axle weights, also when the caravan is hitched. However, to check whether the MTPLM of the caravan is exceeded or not, and that is also a legal limit, one has no option but to unhitch the caravan. In addition, each axle also has its own limits.
 

Sam Vimes

Moderator
Sep 7, 2020
1,819
1,361
5,935
Visit site
What I find curious about this exercise is the preciseness of the result and how it matches 100% the plate rating.

If this happened to me I would be questioning the resolution and accuracy of the weighbridge. Did they actually weigh it correctly or just got a near enough figure to the plate and said yes that's it?

Resolution is how fine the weight increments/decrements can be detected. That is if you added 10kg to the payload or took it out would the result have been 1990 or 2010.

Then there's the accuracy. I took a very quick look and it might be that the DVSA weighbridges could be as inaccurate by as much as plus or minus 100kg. That's a large percentage for a caravan, not so much for a 38 tonne truck.

Commercial weighbridges used by building suppliers for example should be more accurate since they don't won't to give away unnecessary materials due to under weighing.

I don't know the answers to resolution or accuracy but it could be significant when questioning payload.

Then of course the absurd...to me....issue of uprating. You pay the caravan manufacturer for a plate that just has a bigger number on it. There are no structural changes to the caravan. The uprated amount could be less than the weighbridge can accurately record.
 
May 7, 2012
8,598
1,816
30,935
Visit site
Given the weighbridge operator would not have known the MTPLM of the caravan the reading should be correct although subject to any error in the weighbridge. Given this the answer to taking more with you would seem to be load it in the car as you do have some leeway there.
 
Mar 14, 2005
9,837
724
30,935
lutzschelisch.wix.com
Then of course the absurd...to me....issue of uprating. You pay the caravan manufacturer for a plate that just has a bigger number on it. There are no structural changes to the caravan. The uprated amount could be less than the weighbridge can accurately record.

On UK built caravans, the label next to the door seldom displays the true MTPLM that the manufacturer had type approved for your particular caravan. More often than not it's a value for marketing purposes only and the true MTPLM will be found on the statutory weight plate that must be present on all caravans built since 2012. The so-called uprating is actually only to bring the marketing MTPLM in line what was there already.
 
Jul 18, 2017
13,169
3,758
40,935
Visit site
Legislation refers to both axle weight and total weight. Gross train weight, a legal limit, is the sum of all axle weights of the combination, i.e. those of the car and of the caravan. Gross vehicle weight of the car, again a legal limit, is the sum of its front and rear axle weights, also when the caravan is hitched. However, to check whether the MTPLM of the caravan is exceeded or not, and that is also a legal limit, one has no option but to unhitch the caravan. In addition, each axle also has its own limits.
I understand all the above and that the sticker is not a statutory. but a guideline by caravan manufacturers. For any prosecution the officer would need to refer to the statutory plate as per #32. Is there any such term as MTPLM in legislation?
 
Mar 14, 2005
9,837
724
30,935
lutzschelisch.wix.com
I understand all the above and that the sticker is not a statutory. but a guideline by caravan manufacturers. For any prosecution the officer would need to refer to the statutory plate as per #32. Is there any such term as MTPLM in legislation?

Yes, in fact in current legislation it is always called MTPLM, not only for caravans but for all road vehicles. Strictly speaking, the term gross vehicle weight is obsolete.
 
  • Like
Reactions: Buckman
Nov 11, 2009
21,185
6,710
50,935
Visit site
I understand all the above and that the sticker is not a statutory. but a guideline by caravan manufacturers. For any prosecution the officer would need to refer to the statutory plate as per #32. Is there any such term as MTPLM in legislation?
Wasn’t this discussed not very long ago and a link provided to the HMG website under C&U regulations along with Kerbweight. I don’t know why some members are so obsessed with MTPLM, transfer of weight from caravan to car, axle loading. What is it about “ maximum” that’s so difficult to understand. I’m sure if a police officer had concerns the van could be impounded until those concerns had been resolved.
 
Last edited:
  • Like
Reactions: Mr Plodd
Mar 14, 2005
9,837
724
30,935
lutzschelisch.wix.com
The issue, and that is a peculiar UK one, is that many UK built caravans display two MTPLMs, one on the label by the door and another different one on the statutory plate and their owners are unsure which of the two applies. To cover themselves in case of dispute either they stick to the lower of the two values or they apply for a so-called upgrade, which it really isn’t.
Fact is, however, that roadside checks seldom bother to find out whether the MTPLM is exceeded or not, because to do that one would have to unhitch. Nine times out of ten they will only measure the caravan’s axle load and leave it at that.
 
Nov 11, 2009
21,185
6,710
50,935
Visit site
The issue, and that is a peculiar UK one, is that many UK built caravans display two MTPLMs, one on the label by the door and another different one on the statutory plate and their owners are unsure which of the two applies. To cover themselves in case of dispute either they stick to the lower of the two values or they apply for a so-called upgrade, which it really isn’t.
Fact is, however, that roadside checks seldom bother to find out whether the MTPLM is exceeded or not, because to do that one would have to unhitch. Nine times out of ten they will only measure the caravan’s axle load and leave it at that.
I must have been one of the unfortunate 1 in 10 to have been decoupled for a check near Ringwood at a Government highways facility.
 
Mar 14, 2005
17,937
3,303
50,935
Visit site
... I don’t know why some members are so obsessed with MTPLM, transfer of weight from caravan to car, axle loading ...
There are a number of possible offences that an overloaded or incorrectly loaded outfit might fall foul of, whilst still being within the Gross Train Mass limit. As you yourself tell us, you experienced a stop and weigh intervention, and the authorities felt it was necessary to uncouple your caravan, which allowed them assess some of those other concerns that cannot be derived from just an axle load assessment. Compliance with a caravans MTPLM, can only be assessed by uncoupling and weighing one or both parts of the outfit separately. This is necessary becasue of the way nose load is transferred from the trailer to tow vehicle.
 
Nov 11, 2009
21,185
6,710
50,935
Visit site
There are a number of possible offences that an overloaded or incorrectly loaded outfit might fall foul of, whilst still being within the Gross Train Mass limit. As you yourself tell us, you experienced a stop and weigh intervention, and the authorities felt it was necessary to uncouple your caravan, which allowed them assess some of those other concerns that cannot be derived from just an axle load assessment. Compliance with a caravans MTPLM, can only be assessed by uncoupling and weighing one or both parts of the outfit separately. This is necessary becasue of the way nose load is transferred from the trailer to tow vehicle.
You have selectively taken a quote out of context with the rest of my post. It’s not the adherence to the MTPLM I was querying but the fact that it seems that it’s regularly subject to spurious queries about its relevance and legality, if transfer of load to the towbar allows a increase in weight carried in the caravan, etc, and whether the police can enforce it. In some respects my post was TIC. I’m sorry you took it so seriously. As a professional engineer I take safety seriously and I would have thought by now that would have come across.
 
Last edited:
Nov 11, 2009
21,185
6,710
50,935
Visit site
When was that? It could have been me involved!!
I’ve posted about the Ringwood weight check over 20 times and I must be the only one on the Forum to have been subject to an official weight check. It took place circa 2000-2 when I was towing with a Saab 9000 CSE and the caravan was an Eldiss 2 berth GTX Hurricane MTPLM of 1300kg. I was heading east and a police motorcyclist came alongside and flagged me to follow him. Once in the DoT facility he rode off, and all checks were carried out by DoT staff, with police in attendance. The outfit was weighed on the installed weighbridge not using portable weighing devices. I didn’t bother to ask to see its calibration certificate and if it was within calibration dates. 😂😂😂
 
Nov 30, 2022
1,119
946
1,435
Visit site
Around that time I may well have been that motorcyclist, it was an easy gig, find something to weigh, escort it to the checkpoint, then whizz off to find something else to weigh. No paperwork at all!
 
Jul 18, 2017
13,169
3,758
40,935
Visit site
The biggest confusion seems to relate to some people being under the false impression that by taking the load off the jockey wheel and placing it on the towball, the caravan suddenly becomes lighter. Strange logic!
It is strange then that people are asked to decouple the trailer so it can be weighed on its own? Why, if no weight is transferred to the towball? Surely the weight should be the same whether connected onto the towball or not?
 
Mar 14, 2005
9,837
724
30,935
lutzschelisch.wix.com
It is strange then that people are asked to decouple the trailer so it can be weighed on its own? Why, if no weight is transferred to the towball? Surely the weight should be the same whether connected onto the towball or not?
Of course the total weight is the same, but how would you know what portion of that weight is acting on the towball without unhitching and putting the jockey wheel on the scales?
Alternatively, you could weigh the car when it’s hitched to the caravan and again after unhitching. One can then add the difference between those two values to the measured axle load of the caravan.
 
Last edited:
  • Like
Reactions: Saxo Appeal
May 7, 2012
8,598
1,816
30,935
Visit site
One problem with using the uncoupled weight is the axle weight will be different. The front will now use the jockey wheel which is further back so weight will differ from the hitch and the hitch will probably be higher than the weight when hitched adding a further difference. Only by using a hitch weight gadget can you get the hitch weight.
 
  • Like
Reactions: Dustydog
Nov 11, 2009
21,185
6,710
50,935
Visit site
It is strange then that people are asked to decouple the trailer so it can be weighed on its own? Why, if no weight is transferred to the towball? Surely the weight should be the same whether connected onto the towball or not?
Surely weighing the caravan on its own allows the MTPLM to be measured. Weight transfer to the tow car isn’t relevant if you need to obtain the weight of the caravan. The weight transfer to the towball can be a variable. But MTPLM isn’t.
 

TRENDING THREADS

Latest posts