Jump to content
Sign in to follow this  
Pebble

Noseweight & Car Suspension.

Recommended Posts

For whatever reason, the Delta and Clubman seem to be very nose heavy before they're even loaded. Our first noseweight of 135kg is testament to this as, if I'm honest, we did try to keep heavy things over the axles on collection. Same applied to our 2013 Delta which showed 80kg on the nose with nothing inside it - no gas bottles, no clothes, nothing, just a bare 'van from the factory. I guess it's just the way manufacturers build their 'vans - some are light on the front, some are heavy.

 

I've been reading this with interest http://www. google. co. uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwil99yKzv3OAhXIDsAKHXbkD9EQFggcMAA&url=http%3A%2F%2Fwww. caravantalk. co. uk%2Flibrary%2Ffiles%2FBeginners-Guide-To-Towing-Dynamics. pdf&usg=AFQjCNEIw0UFaJ7PZ_9uqx3gdVWirbHrIA&sig2=umHUn9UoOH6cuyE-S-XCjg&bvm=bv. 131783435,d. d24 and the more I re-read it, the more I start to check everything out. Think I need to chill and relax a bit more :ph34r:

 

Hmmm, starting to miss my 5000kg motorhome with a 900kg payload lol.

Edited by Pebble

Share this post


Link to post
Share on other sites

sampvt, you don't need to increase the back weight only the front by either reducing/moving what is carried aft or if essential carrying some mass forward.

The aim is to achieve the requiste NW by masses as close to the axle as possible.

It is more than a simple see-saw, that can get the right NW but here we need also to minimise the amount of the mass that is distant to the axle, ie reduce the flywheel/dumbell/pendulum effect.

 

It is very challenging and not black and white but various greys, just the lower the pendulum effect with a decent NW the better.

Fortunately the car's sideways stiffness [hence wanting high tyre pressures] and the fact that the van is pinned to it means weight forward has less adverse effect than weight aft.

By adverse I mean lowering the frequency the whole will naturally want to sway at. We want that high, because by doing so we are less likely to have overtaking bow waves, side winds and any neccesary line of travel deviation to "excite" that natural frequency. If you excite a natural frequency things just build up energy very quickly; as seen on videos of snaking accidents.

 

Best real life thing is bias as much heavy mass forward the least from the axle needed to get the NW right.

 

-------------------------------------------------------------------

 

Once the van is travelling at a decent speed the van's air drag makes the actual dynamic NW less than with the van static; it is trying to tip it backwards in simple terms. If you double the speed, that tipping back force becomes four times.

 

If that was not bad enough for stability, then the bow wave of a passing vehicle slamming in at typically twice your speed, also creates a four times more than normal tipping force.

 

Accepting that light NWs are bad news then increase it to the maximum you can to do, that will give your best chances that air forces don't cause it to get momentarily too low and invite instability.

 

The rules themselves are simple enough to take on board though it is a challenge to get things right and to minimise stability issues, but knowing where and why you are aiming should help.

Edited by JTQ

Share this post


Link to post
Share on other sites

I don't choose to drive with a lower weight, its just the way the van comes out and I actually load the nose to get to 75kg but adding weight to either the back or the front can create a see saw effect can it not. So many topics on this front and bacl balancing that it gets difficult to read. I weigh my nose weight religiously and just recently Iv left the front water tank full and store my ehu cable in the front just to get the weight up.

 

Adding weight upfront shouldn't create instability, quite the opposite. Adding weight right up the back is likely to cause problems. Single axles, especially, pivot round their axle so moving 10kg from the back and adding it to the front can change the noseweight by 20kg, obviously depending from exactly where it was removed and where it is reinstalled. So moving Aquaroll and Wastemaster from rear shower to forward of the axle, for instance, can change the noseweight by between 15 and 25kg for instance. Twin axles are a bit harder because their wheel platforms want to remain 'flat', so it's more difficult to get the change of weight positioning effect.

Share this post


Link to post
Share on other sites

Seems we might have found the answer. ...............

 

I've just spoken with Vauxhall Fleet Services and, as I was aware, our Insignia is fitted with "Flexride" suspension. Basically, there are three option modes with Flexride - Normal, Tour and Sport. Not that it matters here but Sport is firm damping, Tour is soft and normal is, well, normal and somewhere in the middle of the other two. Normal is the default mode.

 

When I've stood on the tow ball, it's been with the engine off. VX tell me that without the engine running, the suspension is rock hard with no travel. When I've hitched the 'van up, it's always been with the car engine running. Can you see where this is leading to? :blush:

 

With the engine running, the suspension comes to life and has travel/movement or as VX say "continuous damping control". So this is why the rear of the car drops with the 'van hitched up, assuming the engine's running.

 

Mystery solved :) .

You never stop learning on this forum.

 

So is there a engine operated pump for the dampers.

Share this post


Link to post
Share on other sites

Ditto xtrailman. I did wonder if pebble had forgotten to let go of the sky hooks!!

  • Like 2

Share this post


Link to post
Share on other sites

You never stop learning on this forum. So is there a engine operated pump for the dampers.

Not engine operated but self levelling suspensions have an electrically operated compressor to raise or lower the suspension.

See system for BMW but other makes are similar.

http://www. bmw. com/com/en/insights/technology/technology_guide/articles/self_levelling. html

Brian

  • Like 1

Share this post


Link to post
Share on other sites

The recommendation is 5 to 7%.

 

That recommendation is merely based on what's possible with UK cars/caravans - it's certainly not a recommendation of the optimum % noseweight which would be over 10%

Share this post


Link to post
Share on other sites

Where does the 10% come from?

 

Most chassis can only take 100kg.

Share this post


Link to post
Share on other sites

I am not an expert on any of this, but one thing does confuse me. .....

 

When a car sets off pulling a caravan, it puts enormous pressure on the towball, under braking a car has 4 x disc brakes and the caravan weighing roughly the same, has 2 simple drum brakes. Ive seen cars being lifted up by the towball by recovery teams and the bit I don't understand is the towball has a max load of 100kg. It does not compute in my books and if these pressures can and are endured by towballs, why is there such a light load maximum. The other issue I also don't understand is the wind hitting the caravan and lifting it up at the front must negate the towbal loading factor. Its all a bit too weird for me to understand so ill just stay with following the manufacturers advice and leave it at that. lol

Share this post


Link to post
Share on other sites

Where does the 10% come from?

 

Most chassis can only take 100kg.

That's why I referred to UK cars/caravans - as 100kg is all we get - in other parts of the world 350 kg + is regarded as normal.

 

Personally, I take the view that noseweight should be as heavy as possible without exceeding any limits of car or caravan.

Share this post


Link to post
Share on other sites

The nose weight is just that the force placed downward onto the ball then through the structure onto the suspension, and as there will be some rear end over hang the rear axle load sees a bit more than the NW due to leverage.

The enormous forces pulling the van are quite different to the NW. and are designed for.

The braking forces are modest; the van looks after itself except for the small load needed on its over run gear to apply its brakes.

There is nothing wrong with drum brakes in this roll, they are fine for the job unless you are decending Alpine like mountains where discs would better resist "fade".

 

Because the caravan's axle is low down and the wind force on the van's front is up much higher, largly above the cars shadow, it tips the van backwards, same as it would if you run under a too low bridge.

Edited by JTQ

Share this post


Link to post
Share on other sites

A hitch has a maximum warranted weight of 100kg. What that is saying is that the manufacturer has designed it to cope with all the stresses and strains that it will suffer with a noseweight of up to 100kg placed on it. It does not mean that the maximum stress it will bear is 100kg. There is a difference.

 

Effectively if you put more than 100kg onto a hitch with that limit it may, during use, exceed the tolerances built into the design and break or bend, or distort its mounting points on the car.

 

I'm not sure it's a good analogy but compare it to a bridge which has a weight limit for individual vehicles. Sometimes there might be half a dozen vehicles of that weight on the bridge at any one time and it's designed to cope. But put half a dozen overweight vehicles on it and it may collapse.

 

I'm a bit doubtful about the claims of noseweight being reduced by airflow over a rig as speed increases and I know som automotive engineers on CT are too. Personally I don't think we hit a high enough speed for that effect to be all that great and the shape of caravans is all wrong for generating lift, they're more like flying bricks than flying aerofoils.

 

Anybody can pivot a caravan around its axle by its hitch but the majority of the weight is borne by the axle, not by the hitch.

Share this post


Link to post
Share on other sites

That's why I referred to UK cars/caravans - as 100kg is all we get - in other parts of the world 350 kg + is regarded as normal.

 

Personally, I take the view that noseweight should be as heavy as possible without exceeding any limits of car or caravan.

so what is you ladan weight and what is your nose weight

Share this post


Link to post
Share on other sites

so what is you ladan weight and what is your nose weight

The MTPLM of my caravan is 1495 kg - the actual laden weight hopefully under that as I've removed some of its equipment (spare wheel/carrier and bunk bed) and all heavy stuff goes in the car - noseweight is loaded to 95 kg to comply with the limit of 100 kg applicable to most UK caravans.

 

My car, in UK/EU spec, has a maximum noseweight of 140 kg - the same car in Australia is currently 280 kg, having been recently downrated from 350 kg - the UK/EU and Australian towing limits for the car are the same at 3,500 kg.

 

If the caravan permitted it I'd run 140 kg noseweight and if both car/caravan permitted it, I'd run 350 kg.

Share this post


Link to post
Share on other sites

Ditto xtrailman. I did wonder if pebble had forgotten to let go of the sky hooks!!

 

A Maserati I had 15 years ago had Sky Hook adjustable damping.

Always thought it was an odd name for it. .. Italians eh !

 

Laws of physics still applied.

Edited by kilham5

Share this post


Link to post
Share on other sites

The MTPLM of my caravan is 1495 kg - the actual laden weight hopefully under that as I've removed some of its equipment (spare wheel/carrier and bunk bed) and all heavy stuff goes in the car - noseweight is loaded to 95 kg to comply with the limit of 100 kg applicable to most UK caravans.

 

My car, in UK/EU spec, has a maximum noseweight of 140 kg - the same car in Australia is currently 280 kg, having been recently downrated from 350 kg - the UK/EU and Australian towing limits for the car are the same at 3,500 kg.

 

If the caravan permitted it I'd run 140 kg noseweight and if both car/caravan permitted it, I'd run 350 kg.

I presume Australian caravan hitches and towbar/balls and cars are built and labelled to those sort of weights. If so, do they differ in any material way to European versions or is it just a relabel? If it is just a relabel why would European limits be so low, there seems, on the face of it, no obvious reason, not even the odd £50 available for upgrading as in MTPLM's?

Share this post


Link to post
Share on other sites

I presume Australian caravan hitches and towbar/balls and cars are built and labelled to those sort of weights. If so, do they differ in any material way to European versions or is it just a relabel? If it is just a relabel why would European limits be so low, there seems, on the face of it, no obvious reason, not even the odd £50 available for upgrading as in MTPLM's?

 

The Bailey caravans sold in Australia have a completely different chassis.

 

That recommendation is merely based on what's possible with UK cars/caravans - it's certainly not a recommendation of the optimum % noseweight which would be over 10%

 

But where has the over 10% been conjured up from?

From my own experience increasing nose weight can increase the instability.

Not engine operated but self levelling suspensions have an electrically operated compressor to raise or lower the suspension.

See system for BMW but other makes are similar.

http://www. bmw. com/com/en/insights/technology/technology_guide/articles/self_levelling. html

Brian

 

Thanks Brian.

Share this post


Link to post
Share on other sites

The 100kg limit is probably something to do with the ability of the coupling to slide in and out to actuate the brakes. If an electric braking system was used then different rules might apply. I was looking for information regarding such things for our Korando and found an Australian towbar site with a towbar rated at 200kg which is 10% of the 2000kg towing limit similar to BGs 350kg. Looked at a few others and 10% seemed to be the norm.

Share this post


Link to post
Share on other sites

I presume Australian caravan hitches and towbar/balls and cars are built and labelled to those sort of weights. If so, do they differ in any material way to European versions or is it just a relabel? If it is just a relabel why would European limits be so low, there seems, on the face of it, no obvious reason, not even the odd £50 available for upgrading as in MTPLM's?

Australian, and American, versions of cars we get here use specific towbars for their market - so not a relabel

The 100kg limit is probably something to do with the ability of the coupling to slide in and out to actuate the brakes. If an electric braking system was used then different rules might apply. I was looking for information regarding such things for our Korando and found an Australian towbar site with a towbar rated at 200kg which is 10% of the 2000kg towing limit similar to BGs 350kg. Looked at a few others and 10% seemed to be the norm.

Alko sell A-frames/hitches in different weight classes - 100 kg is cheaper hence it's predominate use in UK/EU caravans.

 

I believe the Inos and Euro Airstreams use higher rated A-frames/hitches.

Share this post


Link to post
Share on other sites

About 2010 Elddis Crusaders with the BPW chassis were increased to 150 kg from 100 kg .

 

 

 

Dave

  • Like 1

Share this post


Link to post
Share on other sites

The regulation used for Type approval limits the Vertical force component for the coupler to 10% of 1000 kg or 10% of the max mass whichever is the less, for a Centre axle trailer, thereby limiting the Static "nose weight" to 100kg

Edited by Towtug

Share this post


Link to post
Share on other sites

The regulation used for Type approval limits the Vertical force component for the coupler to 10% of 1000 kg or 10% of the max mass whichever is the less, for a Centre axle trailer, thereby limiting the Static "nose weight" to 100kg

So how come some SUVs have noseweight limits higher than 100 kg - Freelander 2, discovery and VW Touareg to name 3 but there's several others - and Alko do have an A-frame/hitch option higher than 100 kg.

Edited by Black Grouse

Share this post


Link to post
Share on other sites

So how come some SUVs have noseweight limits higher than 100 kg - Freelander 2, discovery and VW Touareg to name 3 but there's several others - and Alko do have an A-frame/hitch option higher than 100 kg.

 

I am quoting the limit for a Centre Axle trailer coupling point.

Individual components on both the trailer and tow vehicles can be higher but a Centre axle trailer is limited to 100kg.

Share this post


Link to post
Share on other sites

I am quoting the limit for a Centre Axle trailer coupling point.

Individual components on both the trailer and tow vehicles can be higher but a Centre axle trailer is limited to 100kg.

So no single axle trailer (Centre Axle Trailer) can have a noseweight greater than 100kg ?

 

And yet some UK caravans are more than that ex-works - going by forum reports.

Share this post


Link to post
Share on other sites

I presume the regulation says nothing about the actual noseweight, either empty or loaded, but limits the coupling to 100kg. The purchaser/user is liable for making sure the weight is below any required limits.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...