twin axle and noseweight

[Paul_5099000]

Ok another thread about nose weight :0 but here goes....

i run a toyota colorado landcruiser and a compass rallye 640.

measuring the noseweight ...

1. level ground...how level ? do i have to put a spirit level on the tarmac ? do the twin axles and the jockey all have to be level with each other ?

2. i understand legs up, but brakes on or off ?

3. hitch height has to be same as when hitched to car..BUT is this the height of the tow ball ie between 13.7 and 16.5 inchs or when the van is attached and the towball is pressed down ?

You see what i have done is placed the gauge at the side of the towball...and within a few mm's the gauge is the same height as the towball ...so do i just place the gauge under the tow hitch and wind the jockey wheel all the way off the ground ?

please be gentle with replies this is driving me nutz !!

 

[Lutz]

1. The ground should be as close as possible to level as judged by the eye. There is no need to go to extremes and use a spirit level.

2. Theoretically, brakes off would be absolutely correct, but I doubt whether having the brakes on makes a measurable difference.

3. The hitch height should be the same as when the noseweight is applied to the towball.

The jockey wheel must, of course, be clear of the ground when measuring noseweight or else it will be taking some of the weight.

 

[ProfJohnL]

Hello Paul,

I will try to be gentle.

Whilst the regulations set limits, the practical application of the test conditions is difficult, so I suggest a number of compromises on facilities with adjustments to limits or measurements that should keep you the right side of the law.

It is also important to note that as you have a large 4x4, certain limits on hitch height may not apply because of the class of vehicle. You would need to consult the DVLA or VOSA office for clarification for your vehicle.

I will assume the limits do apply, but even if they waived or altered, the methods I suggest can still be applied. You will need to establish what limits are applicable to your car and caravan. This includes the maximum nose load limits that both the car and caravan manufacture permit. You have to work to the lower of the two if there is a difference.

The measurements must be carried out on a level road or surface. I would suggest it is level enough if a car/caravan will not roll when the brakes are released. Obviously there should be no other obstruction or debris acting as chocks to prevent rolling when testing the surface. At all other times make sure the brakes are applied.

The EU hitch height limits are 350 to 420mm to the centre of the ball.

The weight distribution in a caravan ensures that the nose load changes if the height of the hitch is changed, The nose load actually increases if the hitch is lowered, so it will be greatest when it is at its minimum allowable height i.e. 350mm

This is helpful because it simplifies the setting method.

By arranging your nose load gauge so it supports the hitch at the minimum height of 350mm, then the actual nose load on the car will always be less than the set load. The variation may not be great but it keeps you legal

The actual load must be measured vertically below the ball hitch. Brake applied (or wheels chocked). The jockey wheel and steadies raised away from the floor so the caravan is only supported on the main wheels and the nose load gauge.

The fact that you have a twin axle does make a difference, in that the change in nose load is more rapid and greater depending on the hitch height, so attention to this detail is important.

Having set the nose load within limits, it is advisable to hitch it to the car, and double check that the hitch remains within the 350 to 420mm EU limit. If it is outside either limit you must check the loading of the car, as you may have exceeded the rear axle load limit.

Whilst it looks good to have the caravan level when hitched to the car, there is no technical reason for it to be ruler level. It can actually ride quite safely in either nose up or down attitude. For some vehicles tow ball dropper plates are allowed, but you must check with your supplier if they are permitted for your vehicle. The overriding criterion is that it is loaded correctly giving the requisite nose load.

I hope this has not been too difficult for you.

 

[Gafferbill]

John L has given you an answer that suits an outfit at rest.

The only time you can check it of course.

Remember that a caravan is a ballanced trailer and has a fulcrum about which it pitches.

Hence the reason noseweight is important.

Unlike on a single axle caravan, on a twin axle this fulcrum can move forward or aft when being towed, considerably effecting noseweight.

The more level the surface the less the effect.

The worst case scenario is when the caravan mounts a fairly steep crest in the road, causing the weight carried by the trailing axle to be reduced and the fulcrum to move forward.

This can cause negative noseweight.

Extra noseweight can be caused if the front axle falls into a dip or gulley

Drivers with twin axles should be aware of this possibility.

 

[Paul_5099000]

ok guys i think its becoming clearer.....

i understand about the level surface or at least level enough so she dont roll away....

now the hitch height....i understand the rule about the towball having to be between 350 and 420 mm

i think mines about 16inches to the top of the ball so half inch off to centre will put me legal and ok with that...

Now measuring the weight...i understand that the hitch must have an amount of noseweight (in line with the lower of the values of nose load for car and caravan) and this nose weight must be in place when the hitch is sitting at the same height as it would if connected to the car......

Now what i have been doing is winding the jockey wheel up high enough to fit the gauge under neath...( the gauge measures the same height as my towball) i then wind down the jockey onto the gauge untill the wheel comes off the floor....this is where im confused....are we saying that when we get the right nose weight, the height of the hitch will fall into the 350-420 area ?

obviously the more weight goes on, the lower the nose becomes and eventually will fall foul of the heights ?

or do i wind down the jockey wheel (with gauge in place) untill i reach the correct height and then just read of the gauge ? (isnt the jockey taking some of this weight then ?)

sobs in a corner i thought i was so close to understanding ..

i need a guro to come show me the error of my ways !

 

[ProfJohnL]

Hello again Paul,

To take your points in order.

Hitch height. The regulations are quoted in ISO measurements of mm, and the critical points are min 350 max 420mm. This is measured to the centre of the ball not the top. The reason being that some ball manufacturers turn a small flat spot on the top. The size of the flat varies, so it would give inconsistent results to measure from it. In Practice you cannot measure to the centre of the ball, but you can check to the horizontal diameter which will have the same vertical displacement as the centre.

Modern tow balls have a nominal diameter of 50mm,so the radius is only 25mm which is close to but not exactly 1 inch (1" = 25.4mm)So you need to subtract about 1 inch not just a half.

You are correct about the hitch sitting at the same height as when it is connected to the car.

Your method of checking the nose load by lowering the hitch onto the gauge by using the jockey wheel is fine, and yes the jockey wheel must be free of the ground so the gauge takes all the load.

And yes for a car that is compliant with EU regs (and all new cars sold in the EU must be)for a nose load of the stated amount the hitch should ride within the prescribed height limits - but do not forget that the ride height is also going to be affected by what's in the car, such as passengers luggage and fuel.

Logically from the above, if a tow hitch falls outside of the height limits, then one has to suspect some incorrect loading somewhere on the outfit, or a mechanical failure in the cars suspension. IN either case you should not tow until the problem has been resolved.

I am sorry if this adds any more confusion, but whilst we have been describing the nose load limits, we havn't said why.

It is generally accepted the controllability of a towing outfit is improved with high nose loads. But that does not mean you have to be at the absolute upper limit. Many outfits are quite controllable with less than the theoretical available limit. So if your limit is 100Kg, you may find it is still perfectly acceptable at only 75Kg, which is a fairly typical limit for most saloon cars.

So if you cannot keep the tow ball height above the 350 lower limit, you may find that by lowering your applied nose load you can bring the tow hitch within range and still have a safe towing experience.

 

[Happy-Lappy]

John.L

I know I'm putting my neck on the block here, but my Towball Height is just above the 420mm limit. The reason for this is that I have MAD Spring Assisters fitted to my Renault Espace, I always have my Noseweight at 80kg which is the max allowed for the car, do you think I should put the EHU and other heavy items in the boot and lower the Noseweight to 75kg

I never tow above 60mph and apart from the normal buffeting effect, I don't have any stability concerns.

My Caravan is a T/A Lunar Quasar615,

thanks in advance, Martin

 

[ProfJohnL]

Hello happy lappy,

Quite bluntly your outfit is illegal. the tow ball by your own description is above the top limit specified by the EU. and that means your insurance will also be void whilst towing.

In this case the spring assisters are not doing you any favours.

If you are already at the maximum nose load you cannot add anything to the front of the caravan. The only solution is to remove or reduce the assistance the assisters give.

I currently run a phase 3 Grande Espace, without assisters, and I do not find a problem with ball height.

 

[ProfJohnL]

Hello happy lappy,

Quite bluntly your outfit is illegal. the tow ball by your own description is above the top limit specified by the EU. and that means your insurance will also be void whilst towing.

In this case the spring assisters are not doing you any favours.

If you are already at the maximum nose load you cannot add anything to the front of the caravan. The only solution is to remove or reduce the assistance the assisters give.

I currently run a phase 3 Grande Espace, without assisters, and I do not find a problem with ball height.

I should add that Renault tend to specify max train weights that compromise the max loads you can have in either the car or the caravan.

If you rear suspension is too soft as standard, then you should check your axle loading, To tow a trailer of maximum MTPLM you cannot load the car, and vice-verca.

 

[Happy-Lappy]

John L

In reply to your comments, this leaves me with two options:-

1. Have the Spring Assisters taken out

2. Put extra ballast in the boot of the car to lower the rearsprings

I could go back to using the normal 6kg Calor Bottles and then remove any other heavy items from the front locker to the boot.

I don't want to have to change cars yet, as I still use all seven seats on occasions, but if I can't get the height down, then maybe I should look at replacing the original suspension (after removing the assisters),

thanks for the advice and best regards, Martin

 

[Paul_5099000]

Hello again Paul,

To take your points in order.

Hitch height. The regulations are quoted in ISO measurements of mm, and the critical points are min 350 max 420mm. This is measured to the centre of the ball not the top. The reason being that some ball manufacturers turn a small flat spot on the top. The size of the flat varies, so it would give inconsistent results to measure from it. In Practice you cannot measure to the centre of the ball, but you can check to the horizontal diameter which will have the same vertical displacement as the centre.

Modern tow balls have a nominal diameter of 50mm,so the radius is only 25mm which is close to but not exactly 1 inch (1" = 25.4mm)So you need to subtract about 1 inch not just a half.

You are correct about the hitch sitting at the same height as when it is connected to the car.

Your method of checking the nose load by lowering the hitch onto the gauge by using the jockey wheel is fine, and yes the jockey wheel must be free of the ground so the gauge takes all the load.

And yes for a car that is compliant with EU regs (and all new cars sold in the EU must be)for a nose load of the stated amount the hitch should ride within the prescribed height limits - but do not forget that the ride height is also going to be affected by what's in the car, such as passengers luggage and fuel.

Logically from the above, if a tow hitch falls outside of the height limits, then one has to suspect some incorrect loading somewhere on the outfit, or a mechanical failure in the cars suspension. IN either case you should not tow until the problem has been resolved.

I am sorry if this adds any more confusion, but whilst we have been describing the nose load limits, we havn't said why.

It is generally accepted the controllability of a towing outfit is improved with high nose loads. But that does not mean you have to be at the absolute upper limit. Many outfits are quite controllable with less than the theoretical available limit. So if your limit is 100Kg, you may find it is still perfectly acceptable at only 75Kg, which is a fairly typical limit for most saloon cars.

So if you cannot keep the tow ball height above the 350 lower limit, you may find that by lowering your applied nose load you can bring the tow hitch within range and still have a safe towing experience.

Hi John L many thanks for your patience,,,i WILL get this sooner or later

a point....like i say when i check my nose weight at the moment, i raise the van on the jockey whell high enough to fit the gauge underneath and then lower onto gauge......

Now my problem...if we are talking about loading it to the lower height limit of 13.7 inchs (350mm) then my gauge is approx 16inches tall !! If i stand the gauge next to the tow ball they are the same height...

My point is if i wound down my van hitch on the jockey wheel to 350mm the gauge wouldnt fit underneath,.,,,or have i gone right of the rails here!

thanks again for your help its much appreciated...

Paul.

 

[ProfJohnL]

Hi yet again Martin,

You have twice referred to moving mass from the front of the caravan to the rear load area of the car, I am puzzled as to what you think that will do?

Your problem is that with the the assister's your rear suspension is too tall which raises the tow ball. If you lighten the caravans nose load, you will be reducing the depressive effect it has so the hitch will not sink as far, and it will be even more out of range and in addition you may find the outfit becomes more difficult to control.

If the mass you have removed from the caravan is then put in the car, its effect on the rear suspension will be less than when it was in the caravan, so even that does not address the fundamental problem.

The only solution is to remove the spring assister. The car should not need them to address an height issues, but I do concede that the rear suspension does wallow a bit so some added stiffness may make it ride better - higher rated shock absorbers may be a better solution.

I feel I must point out that that if the towball sinks too low without the spring assisters, firstly check the loads in both the car and the caravan are not over limit, and then suspect the mechanics such as suspension.

Overloading loading is just as illegal and may have significant safety implications. Again Renault are not generous with their limits for axle loads and Gross train weight, so do double check you loads against the limits.

 

[Paul_5099000]

Hi John L many thanks for your patience,,,i WILL get this sooner or later

a point....like i say when i check my nose weight at the moment, i raise the van on the jockey whell high enough to fit the gauge underneath and then lower onto gauge......

Now my problem...if we are talking about loading it to the lower height limit of 13.7 inchs (350mm) then my gauge is approx 16inches tall !! If i stand the gauge next to the tow ball they are the same height...

My point is if i wound down my van hitch on the jockey wheel to 350mm the gauge wouldnt fit underneath,.,,,or have i gone right of the rails here!

thanks again for your help its much appreciated...

Paul.

 

[Lutz]

If the noseweight gauge won't fit under the coupling when the coupling is at the same height as when the caravan is hitched up to the car, I'm afraid there is something wrong with the design of the gauge.

 

[ProfJohnL]

Hi Paul,

I sense that I have not explained things sufficiently clearly,

Lets try a slightly different approach:

For best towing, you need to load your caravan so it produces sufficient nose weight at the hitch. In general it is accepted that the Nose Weight should be reasonably high but obviously within the limits allowed for the car and the caravan.

The limits are defined by the tow bar specification and the caravan manufacture. You will need to check you actual limits but as you have a large 4x4 so the tow bar limit is usually in excess 100Kg, (most saloon cars are only about 75Kg) and the caravan chassis are usually limited to 100Kg .

So assuming I am right about your tow bar limit being over 100Kg, the limiting factor is the caravan at 100Kg. (for most saloons it is the tow bar that limits the weight) This is the maximum Nose Load.

As you can imagine, putting such a load on the tow ball along with al the passengers luggage and fuel is going to cause the cars rear suspension to compress and as it does so the tow ball will settle to a particular height. For saloon cars that height must fall be between 350 to 420mm measured to the centre of the ball.

It is usually unwise to load to the absolute limit, so I would suggest aiming for about 85Kg nose load in your case. (this lower figure is not cast is stone).

Now, how to measure the nose load. I suggest setting the gauge to 350mm. The checking the nose load at hat fixed height. This is because as the caravan's hitch is raised or lowered the actual measure nose load value will change, and it is at a maximum when the hitch is lowest. Given that the EU Regs lower limit is 350mm I choose that. If you cannot adjust the height gauge, then it is not fit for purpose.

The benefit is that as all legal tow ball height are between 350 and 420 any measurement taken of the caravan will always be less than the maximum allowed, and thus keep the outfit nose load legal.

Once the caravan nose load is set, attach it to the car as if ready to tow and check the height of the tow ball. If everything is all right, then the hitch will settle between 350 and 420mm. If it is outside of the limits recheck all your loads, and adjust some is necessary but never exceed any limits.

 

[Happy-Lappy]

Hi yet again Martin,

You have twice referred to moving mass from the front of the caravan to the rear load area of the car, I am puzzled as to what you think that will do?

Your problem is that with the the assister's your rear suspension is too tall which raises the tow ball. If you lighten the caravans nose load, you will be reducing the depressive effect it has so the hitch will not sink as far, and it will be even more out of range and in addition you may find the outfit becomes more difficult to control.

If the mass you have removed from the caravan is then put in the car, its effect on the rear suspension will be less than when it was in the caravan, so even that does not address the fundamental problem.

The only solution is to remove the spring assister. The car should not need them to address an height issues, but I do concede that the rear suspension does wallow a bit so some added stiffness may make it ride better - higher rated shock absorbers may be a better solution.

I feel I must point out that that if the towball sinks too low without the spring assisters, firstly check the loads in both the car and the caravan are not over limit, and then suspect the mechanics such as suspension.

Overloading loading is just as illegal and may have significant safety implications. Again Renault are not generous with their limits for axle loads and Gross train weight, so do double check you loads against the limits.

John L

What I meant was, if I go back to using the normal 6kg Calor Bottles (as opposed to the present calorlite ones) and still keep the noseweight at 75-80kg I then put any additional heavy items, that are normally kept in the caravan in the boot,

best regards, Martin

PS. When I had the assisters fitted, I should have went for the standard ones and not the heavy duty.

 

[Paul_5099000]

Hi Paul,

I sense that I have not explained things sufficiently clearly,

Lets try a slightly different approach:

For best towing, you need to load your caravan so it produces sufficient nose weight at the hitch. In general it is accepted that the Nose Weight should be reasonably high but obviously within the limits allowed for the car and the caravan.

The limits are defined by the tow bar specification and the caravan manufacture. You will need to check you actual limits but as you have a large 4x4 so the tow bar limit is usually in excess 100Kg, (most saloon cars are only about 75Kg) and the caravan chassis are usually limited to 100Kg .

So assuming I am right about your tow bar limit being over 100Kg, the limiting factor is the caravan at 100Kg. (for most saloons it is the tow bar that limits the weight) This is the maximum Nose Load.

As you can imagine, putting such a load on the tow ball along with al the passengers luggage and fuel is going to cause the cars rear suspension to compress and as it does so the tow ball will settle to a particular height. For saloon cars that height must fall be between 350 to 420mm measured to the centre of the ball.

It is usually unwise to load to the absolute limit, so I would suggest aiming for about 85Kg nose load in your case. (this lower figure is not cast is stone).

Now, how to measure the nose load. I suggest setting the gauge to 350mm. The checking the nose load at hat fixed height. This is because as the caravan's hitch is raised or lowered the actual measure nose load value will change, and it is at a maximum when the hitch is lowest. Given that the EU Regs lower limit is 350mm I choose that. If you cannot adjust the height gauge, then it is not fit for purpose.

The benefit is that as all legal tow ball height are between 350 and 420 any measurement taken of the caravan will always be less than the maximum allowed, and thus keep the outfit nose load legal.

Once the caravan nose load is set, attach it to the car as if ready to tow and check the height of the tow ball. If everything is all right, then the hitch will settle between 350 and 420mm. If it is outside of the limits recheck all your loads, and adjust some is necessary but never exceed any limits.

Hi JohnL

http://cgi.ebay.co.uk/HEAVY-DUTY-CARAVAN-TRAILER-NOSE-WEIGHT-GAUGE-NOSEWEIGHT_W0QQitemZ190257438403QQcmdZViewItem?hash=item190257438403&_trkparms=72:1301|39:2|66:2|65:12|240:1318&_trksid=p3286.c0.m14#ebayphotohosting
the above is the gauge i have got...its height is not adjustable at all..and it measures approx 16 inchs from tip to toe...so how would i be able to set this type of gauge to 350mm ?

without digging it into a hole ?

best regards (and sorry to be a pain )

 

[ProfJohnL]

Hello Paul,

Thank you for the link.

It is my view that the gauge is not fit for purpose, as it cannot be set to match the height of the towball or to th elower EU limit of 350mm It therefore cannot tell what you nose load is when the caravan is attached to your car.

My preferred method is to use a pre cut length of pole which I use in conjunction with a flat piece of wood to spread the load and a pair of bathroom scales. The pole is cut so that the the hitch is at 350mm when the pole is set on the spreader and the scales.

I do check the scales for accuracy from time to time by using 25Litre plastic water carrier (weight1Kg) filled with 25 Litres of water = 26Kg

 

[Paul_5099000]

Hello Paul,

Thank you for the link.

It is my view that the gauge is not fit for purpose, as it cannot be set to match the height of the towball or to th elower EU limit of 350mm It therefore cannot tell what you nose load is when the caravan is attached to your car.

My preferred method is to use a pre cut length of pole which I use in conjunction with a flat piece of wood to spread the load and a pair of bathroom scales. The pole is cut so that the the hitch is at 350mm when the pole is set on the spreader and the scales.

I do check the scales for accuracy from time to time by using 25Litre plastic water carrier (weight1Kg) filled with 25 Litres of water = 26Kg

Hi JohnL

thanks for your message....ive seen lots of these type of gauges, plus the type that sit between the tow ball and the hitch, ive often thought that this type alters the ride height under test,,,,

i was checking the nose weight of my brotehrs van at the weekend (a single axle) it started over 100Kg empty !! we finished up having to put the spare wheel and his awning right at the back in order to achieve 85Kgs and even then the kitch was 340mm ! but without adding balast (weight he wouldnt take away on holiday) what can you do ?

at least with the twin i have the opposite problem of having to move stuiff forwards to gain a positive weight.

regards

Paul.