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#1 bopeep

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Posted 19 October 2013 - 04:14 PM

I have sort of asked this before but never really had an answer

A guide is 85 percent of the kerb weight which is easy to understand. Some of the larger cars are able to tow up to 3 and 3500 kg according to the handbook, yet the kerb weight is still only around the 2000kg weight making it towing at over 100 percent.

This I fail to get my head round, the new range rover sport is an example towing limit 3500 kerb weight 1900. I have tried on the net to solve this puzzle but it just says do not exceed the kerb weight.

Can anyone enlighten me please as I am getting confused with what the figures mean.

Thanks

#2 BrianI

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Posted 19 October 2013 - 04:24 PM

The 85% recommendation is for towing a caravan. The manufacturers towing figure is for ANY trailer and is based on the ability to restart on a 12% gradient. It takes no account of stability. However it does give an indication of towing ability.

 

There is a big difference in towing a caravan, with a large area exposed to cross winds, to towing a builders trailer full of bricks with a low centre of gravity. 

 

Brian



#3 ericfield

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Posted 19 October 2013 - 04:36 PM

85% was a figure derived some years ago as a 'rule of thumb' for tow vehicles mainly based on their ability to do a specified hill start with caravan attached.

Since then, cars have become more powerful, more aerodynamic with improved braking performance. All of which make many modern cars more ABLE to tow heavier loads than 85% of their kerbweight.

But in addition to whether a car is CAPABLE of towing heavier loads, there is the overriding question of is it safe to do so?

Manufacturers refer to 'trailers' not caravans. There is a world of difference in towing a 2ton trailer and a 2ton caravan, where wind resistance and higher centres of gravity make the caravan a 'less stable' option.

Whilst the 85% 'rule of thumb' may be outdated (I tow with a 4x4 at 96%) it's still a good starting point for matching tugs and caravans, especially if you are an inexperienced tower. As to what the carweight used in this calculation should be.....personally I feel that's straining at gnats. I take the V5C declared mass and ignore all other figures.

As Brian says.....I took to long to type my reply. LOL

Edited by ericfield, 19 October 2013 - 04:37 PM.


#4 Steamdrivenandy

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Posted 19 October 2013 - 04:56 PM

This situation of cars being able to pull much more than their weight is set to be a growing issue.

 

Car makers are working hard to make their cars lighter in order to improve economy, whilst making engines more powerful for any given size for the same reason. So more powerful engines driving lighter bodies will mean that cars can drag more weight. However a very light car, in lots of circumstances is not a good thing from a stability point of view.

 

I suppose a good analogy would be that a fully lightened and tuned GT race car could probably pull a caravan without a problem, but put it in a gale on a motorway with masses of heavy goods vehicles and rain lashing down on a downhill stretch it would probably pirouette round the caravan or vice versa.   



#5 CommanderDave

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Posted 20 October 2013 - 08:58 AM

Vehicles pulling heavier loads is not a problem as an example there are Isuzu mini tractor units with a kerbweight of 2000kg and a towing limit of 11000Kgs and with a 3LR engine. As said it is stability and stopping is the main problem.

While cars are getting more powerful and lighter caravans have become heavier with people wanting more gadgets.

Dave

#6 ericfield

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Posted 20 October 2013 - 01:31 PM

.....
While cars are getting more powerful and lighter caravans have become heavier with people wanting more gadgets.
Dave


I like to think that caravan weights have peaked. Manufacturers now seem to be trying to reduce weights through new materials and manufacturing methods...and I am unsure there is anything else gadget wise left to fit.

#7 Alsie

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Posted 20 October 2013 - 01:46 PM

IMO the difference is the "Technical permissable maximum towable mass of the trailer" in the Range Rover Sport is 3500 kg which means that is the wait technically speaking the car an tow but the 85% rule against kerb weight of 1900 kg suggest that a trailer weight of 1615 kg is safest weight to tow according to the Caravan Club.

I could be wrong but that is my interpretation.

#8 CommanderDave

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Posted 20 October 2013 - 02:18 PM

I like to think that caravan weights have peaked. Manufacturers now seem to be trying to reduce weights through new materials and manufacturing methods...and I am unsure there is anything else gadget wise left to fit.


Not sure on that one by looking at the order books for Eterniti caravans for slide outs?


Dave

#9 Alan Stanley

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Posted 20 October 2013 - 04:57 PM

I have sort of asked this before but never really had an answer

A guide is 85 percent of the kerb weight which is easy to understand. Some of the larger cars are able to tow up to 3 and 3500 kg according to the handbook, yet the kerb weight is still only around the 2000kg weight making it towing at over 100 percent.

This I fail to get my head round, the new range rover sport is an example towing limit 3500 kerb weight 1900. I have tried on the net to solve this puzzle but it just says do not exceed the kerb weight.

Can anyone enlighten me please as I am getting confused with what the figures mean.

Thanks

Keep it simple.

 

Car manufacturers publish a towing weight that is defined by what they say the vehicle can pull up a predefined slope without suffering mechanical problems and invalidating your warranty.  

They have no relationship to the real world problems of towing say a caravan.   So the 85  %  guideline arose.  It's not a rule, it's not a law.  Just a common sense starting point for those who are not experienced.

 

Land Rover and others make vehicles with towing heavy loads in mind and therefore have towing limits substantially above other types of car.  Look at this VW on utube.

 

http://www.youtube.com/watch?v=ls23tHPX8mQ 

 

The problem with caravans are that they are a big sail, with weight high up so they are inclined to wag about given the chance and this is not good.  The car needs to be able to control this so the recommended 85% is a good starting point.  



#10 muddy250

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Posted 21 October 2013 - 01:10 PM

85% was a figure derived some years ago as a 'rule of thumb' for tow vehicles mainly based on their ability to do a specified hill start with caravan attached.

Since then, cars have become more powerful, more aerodynamic with improved braking performance. All of which make many modern cars more ABLE to tow heavier loads than 85% of their kerbweight.

But in addition to whether a car is CAPABLE of towing heavier loads, there is the overriding question of is it safe to do so?

Manufacturers refer to 'trailers' not caravans. There is a world of difference in towing a 2ton trailer and a 2ton caravan, where wind resistance and higher centres of gravity make the caravan a 'less stable' option.

Whilst the 85% 'rule of thumb' may be outdated (I tow with a 4x4 at 96%) it's still a good starting point for matching tugs and caravans, especially if you are an inexperienced tower. As to what the carweight used in this calculation should be.....personally I feel that's straining at gnats. I take the V5C declared mass and ignore all other figures.

As Brian says.....I took to long to type my reply. LOL

 

Thank You! Why did I never think in all this time to look at the damn V5 to find out definitively what my towing limit is?

Whataburke. :blink:



#11 CommanderDave

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Posted 21 October 2013 - 03:58 PM

IMO I think the 85% recommendation is summed up in what some other countries call our "over run brakes" as they call them "surge brakes" which I think is a good description for them as the tow vehicle has to stop the caravan surging towards it and needs as much ballast as it can have against the oncoming force .


Dave

Edited by CommanderDave, 21 October 2013 - 03:59 PM.


#12 Lutz

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Posted 21 October 2013 - 04:34 PM

IMO I think the 85% recommendation is summed up in what some other countries call our "over run brakes" as they call them "surge brakes" which I think is a good description for them as the tow vehicle has to stop the caravan surging towards it and needs as much ballast as it can have against the oncoming force .


Dave

 

The caravan's brakes should be perfectly capable of stopping the caravan on its own with only a minimum of support fromn the towing vehicle, just enough to actuate the overrun brake, and that shouldn't be much.


Edited by Lutz, 21 October 2013 - 04:35 PM.


#13 Steamdrivenandy

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Posted 21 October 2013 - 04:46 PM

I think what Dave is saying is that the heavier the towing vehicle the less likely that an emergency stop will cause instability in the whole rig. I'm sure the brakes will come on quickly and everything should stop in time etc, but that millisecond when the weight of the van transfers into the opposite direction from normal can lead to skids etc if the towcar is lightweight.



#14 xtrailman

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Posted 22 October 2013 - 07:17 AM

85% was a figure derived some years ago as a 'rule of thumb' for tow vehicles mainly based on their ability to do a specified hill start with caravan attached.

Since then, cars have become more powerful, more aerodynamic with improved braking performance. All of which make many modern cars more ABLE to tow heavier loads than 85% of their kerbweight.

But in addition to whether a car is CAPABLE of towing heavier loads, there is the overriding question of is it safe to do so?

Manufacturers refer to 'trailers' not caravans. There is a world of difference in towing a 2ton trailer and a 2ton caravan, where wind resistance and higher centres of gravity make the caravan a 'less stable' option.

Whilst the 85% 'rule of thumb' may be outdated (I tow with a 4x4 at 96%) it's still a good starting point for matching tugs and caravans, especially if you are an inexperienced tower. As to what the carweight used in this calculation should be.....personally I feel that's straining at gnats. I take the V5C declared mass and ignore all other figures.

As Brian says.....I took to long to type my reply. LOL


That's ok assuming the V5c is accurate which it isn't always.

Mine says 1490kg which doesn't match any other published figures.

Mazda have confirmed my kerb weight as 1663kg, includes driver.



#15 xtrailman

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Posted 22 October 2013 - 07:23 AM

Thank You! Why did I never think in all this time to look at the damn V5 to find out definitively what my towing limit is?

Whataburke. :blink:

You can't use it to determine your towing limit, only your ratio.

 

The car manufacturer determines the cars tow limit, and also for some the license category.



#16 muddy250

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Posted 22 October 2013 - 01:14 PM

You can't use it to determine your towing limit, only your ratio.

 

The car manufacturer determines the cars tow limit, and also for some the license category.

 

So even the DVLA have it wrong. It's not as simple as it looks is it.

Car plate says MAM 1936kg GTW 3436kg. I bet you can't just subtract the one from the other either can you.

 

To make matters ever more confusing my car kerb weight is quoted without driver and 75kg has to be added to get the match figure right. Good grief....



#17 Lutz

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Posted 22 October 2013 - 01:52 PM

 

So even the DVLA have it wrong. It's not as simple as it looks is it.

Car plate says MAM 1936kg GTW 3436kg. I bet you can't just subtract the one from the other either can you.

 

To make matters ever more confusing my car kerb weight is quoted without driver and 75kg has to be added to get the match figure right. Good grief....

 

Whether the entry in the V5c is right or wrong, it will always include 75kg for the driver, because that's the definition of Mass in Service (or Mass in Running Order).



#18 leedslad

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Posted 22 October 2013 - 02:00 PM

The 85% recommendation is for towing a caravan. The manufacturers towing figure is for ANY trailer and is based on the ability to restart on a 12% gradient. It takes no account of stability. However it does give an indication of towing ability.

 

There is a big difference in towing a caravan, with a large area exposed to cross winds, to towing a builders trailer full of bricks with a low centre of gravity. 

 

Brian

:goodpost:       John.



#19 muddy250

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Posted 22 October 2013 - 02:34 PM

 

Whether the entry in the V5c is right or wrong, it will always include 75kg for the driver, because that's the definition of Mass in Service (or Mass in Running Order).

There are two definitions for mine, minimum kerbweight and service with 75kg difference.

 

All my figures have just been confirmed by the dealer and my towing limit is 1500kg as plated and on the V5C not 1300kg and in the generic towing guide.

So that's me done and dusted. :-)


Edited by muddy250, 22 October 2013 - 02:51 PM.





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