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Discussion Starter · #1 ·
Right,
Problem is I've got an 18ft tandem axle trailer and behind the Navara, it really seems to amplify any bumps to the point that it is difficult to speak because of shudder! :shock:

First thing done was a check of the trailer / tyres / brakes and all is well.

Then I shimmed the front axle of the trailer with 0.5in spacers. This effectively raises the drawbar by 3in with both trailer axles equally loaded. (I was hoping this would work as it raised the drawbar so that it was matching the setup on my Range Rover) - In reality, little difference.

Then I've bought a flange type towbar and swapped the swan neck for the flange attachment (Note: The rest of the bar is identical so its literally a 5min job with two 19mm spanners). The ball sits at exactly the same height with both types.

Tonight, I fitted a 4in drop plate. (The flange type has too deep a flange to allow a 2in drop plate). Took it out for a spin - if anything its worse!!

So next, I'm going to change out the rubbish back springs and shocks to see if it will calm down....

If anyone wants a swan neck type towbar (OEM Nissan Part), let me know / make me an offer as I now have a spare that will soon be going on EBay!
 
G

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how 'tight' is the socket of the trailer? I had a worn out one, replaced with nice shiney new one, and it is a lot better.

try - as an experiment - lashing the socket to the ball or below (dont do any tight turns ;) - and see if the noise is better - if it is, the socket is worn, and its slapping about. maybe theres some adjustement there?
 

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what sort of suspension does the trailer have?

is the tow vechile loaded/unloaded? trailer loaded/unloaded?

the bumps worse/bett/same uphill or downhill ??
 

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Discussion Starter · #4 ·
There is no play on the socket and the trailer still tows very well behind the Rangie. The trailer has beam axles with Indespension style units on the end.

Its not noise, its a bone shaking up & down movement which I guess is because the empty trailer is quite stiff / bouncy and transfers that through the bar. Normally, I suppose the towing vehicle damps it out.

I am getting more and more convinced its the shocks just are not man enough.
 

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I have exactly the same problem with my twin Axel trailer
but Only after i changed the wheels / Tyres on the trailer.

The trailer came with Michelin Tyres and were 8 years old and starting to perish, so i needed wheels as well as they were rusty.


So i bought a set of replacement wheels tyres, Not the most expensive ones i hasten to say, as its only a trailer :lol:

But now i get the Shakes, it drives me crazy, its only if the trailer is empty though.

I'm going to try and lower the pressure in the trailer tyres ........

I did have to tighten up the two bolts which hold the towbar onto the back of the Nav as you could hold the ball and move it up and down a few mil.
 
G

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go over all the bolts - a week after i fitted my towbar, i went round and tightnend them all again - many were surprisingly loose. :shock:
 

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Dunc,
i tow a 12ft tandem trailer 80% of the time grossing well over 2 tonnes, depending how it is loaded depends how much "bounce "i get. but i fitted a Dixon-Bate Shock Link and that takes most of the rough ride out. Expensive but worth it £400 + VAT !!!

Mark
 

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Must agree with MJ, the shock link is worth every penny.
 

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sounds like its just the difference in cab mountings. shocks on the ute won't do anything as the vibration is via the chassi not the ute tires.

the trailers we normally use crash and bang a lot exspesilly when empty. how well the brake system works makes a big difference to. when loaded you don't notice the trailer is even there.

what sort of brake system do you guys run over there?
got a pic of the suspension?
 

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Discussion Starter · #10 ·
Tweak'e,
Its cable operated over-run brakes on all four wheels through an Indespension auto-reverse hitch.

Don't quite agree with your thought on the shocks :wink: My thought is that they are there to damp out any differential movement between the body / chassis and the axles, doesn't matter where it comes from. The firmness of the unladen trailer suspension and hard tyres probably causes it to bounce a bit but as long as the rear springs on the Nav are not maxed out, the shocks should either prevent or quickly damp out the problem.

I've taken a sstep by step approach and so far eliminated trailer condition (brakes, tyres, geometry) and hitch height.

Next = Shocks, take it for a spin, Springs then take it for a spin... :wink:

I'll keep you posted...
 

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Dunc said:
Tweak'e,
Its cable operated over-run brakes on all four wheels through an Indespension auto-reverse hitch.
errr........what ?????
Don't quite agree with your thought on the shocks :wink: My thought is that they are there to damp out any differential movement between the body / chassis and the axles, doesn't matter where it comes from. The firmness of the unladen trailer suspension and hard tyres probably causes it to bounce a bit but as long as the rear springs on the Nav are not maxed out, the shocks should either prevent or quickly damp out the problem.
shocks are there to dampen out the vibrations in the springs. thats it.
it damaben out impacts on the wheel because the impact is inbetween the shock and the chassi. with the trailer the impact is directly on the chassi bypassing the shocks. basicly that trailer hitch in the link before is a basic shock/spring that goes inbetween the chassi and the trailer.

the other thing is whats is the size and weight of the rangie? also whats the springs like, soft lots of travel? it could well be the trailer was pushing the rangie around a bit and soaking up the bumps. the D40 is a bigger steader vechile and proberly not as soft suspension (harder springs, less travel) so it dosn't get pushed around by the trailer. sorry only a stab in the dark as we don't have many rangies around here.

still i would be interested to see your guys kind of trailer setup.

this is our comman tandam setup...
springs http://www.trojan.co.nz/index.asp?PageID=2145833592
brake/coupling http://www.trojan.co.nz/index.asp?pageID=2145834345
no idea if itss the same or different to what you guys use.
 

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Discussion Starter · #12 ·
[quote:3hswntkx]Dunc wrote:
Tweak'e,
Its cable operated over-run brakes on all four wheels through an Indespension auto-reverse hitch.
errr........what ????? [/quote:3hswntkx]

The overrun brakes in your link convert differential movement at the coupling into hydraulic flow to operate the brakes. Mine are the same except the differential movement pulls a cable which goes to a distribution point where it pulls 4 cables via some levers, these cables then operate the brakes. (Similar to the Nav handbrake).

shocks are there to dampen out the vibrations in the springs. thats it.
it damaben out impacts on the wheel because the impact is inbetween the shock and the chassi. with the trailer the impact is directly on the chassi bypassing the shocks. basicly that trailer hitch in the link before is a basic shock/spring that goes inbetween the chassi and the trailer.
My turn: what ????

So, if I understand your theory, you are suggesting that if I stood in the back of the Navara and jumped up and down, the vehicle body movement would not be damped by the shock absorbers? That would be the case in a gravity free environment I suppose but not on this side of planet earth...
 
G

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if you jumped up and down in the back, someone sitting in the cab would feel the vibrations/ shocks.


the traielr is attched directly to the chassis, as is your ****. so you feel shocks from the trailer as if it were in the back of the nav itself.

the idea of the damped hitch is to separate the two things - a bit like attaching the trailer to the axle, not the chassis.
 

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Discussion Starter · #14 ·
I am obviously doing a **** job at explaining my point of view.... If the back of the Nv moves up and down, the shocks have to scope in/out therefore hopefully, damping the movement.

If you disconnect the shocks, the travel will be further and for a lot longer because the string is undamped.

Proof will be when I change the shocks out, how about we wait until then - if there is no difference, I'll think about buying a hitch damper.

The damper you are referring to is not of the anti-snake variety is it? because that is for horizontal movement so won't make any difference...
 

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I agree with MJ and Lofty.
We use a 16ft flatbed trailer behind our Isuzu Rodeo and since last Christmas have had a Dixon-Bate Shocklink fitted. Certainly reduces (but does not eliminate) a large amount of vertical shock.

One of the problems from what we have experienced is due to the huge leverage / distance between the trailer axles and the rear axle of the vehicle. Over this kind of distance (approximately 17ft in our case) a pothole will be exacerbated hugely. Before the Shocklink we shimed the trailer coupling height (to make the trailer bed level in a neutral position and altered the trailer tyre pressures many times). It certainly helped but the Shocklink certainly improves the ride when empty. If you watch in the side mirrors you can see the front the trailer bobing up and down independtly of the vehicle. Sometimes I look for the odd road hump to see how much it alters!

Was just wondering MJ, Lofty, and any other Shocklink users, how often you grease (and what grease do you use?) on your Shocklink? Have been applying a silcone grease roughly every 1,000 miles (as recommended) but sometimes we notice that it seems to almost seize up in one position. You can jump on the trailer A frame near the coupling and it won't budge yet other times it will move up and down effortlessly. Have you found this at all? Not sure if its working correctly. Sometimes can feel that its not sliding up and down when the ride particularly bad. Was wondering if more or less grease may help?

Would be very greatful of your comments

Thanks
Nav 1
 

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My turn: what ????

So, if I understand your theory, you are suggesting that if I stood in the back of the Navara and jumped up and down, the vehicle body movement would not be damped by the shock absorbers? That would be the case in a gravity free environment I suppose but not on this side of planet earth...
the springs counter the body movement NOT shocks. shocks are to dampen vibration out of the springs. however as shocks do tend to be pressurised they do add a bit of spring to the equation.

the traielr is attched directly to the chassis, as is your ****. so you feel shocks from the trailer as if it were in the back of the nav itself.
thats exactly it.

if you want to mess with shocks it would be FAR better to add them to the trailer. dampen the vibration at the source, the trailer suspension. also have a play with the spring rates.
 

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I can never understand why some trailer manufacturers have not introduced some kind of independent air bag suspension system on the axles. Incorporating an integral compressor system (perhaps powered through a second trailer plug socket or ?) into the trailer surely would not be particularly difficult to do and could reduce weight compared with leaf springs.

At least why do they not install a small airbag fitted between the 'A' frame and the coulpling by way of a pivot. Would surely dampen the loads significantly and only require minimal engineering adaption / cost.
This way you could alter the airbag pressure according to how much payload and nose weight you have to improve the ride accordingly.

Currently, leafsprings on IFor Williams trailers are far too noisey while Avon ride rubber supesnsion (like on our Bateson trailer) just don't absorb the bumps or have enough travel (only about an 1" or so maximum travel).

I think most of the shock problems are trailer suspension related because the manufacturers have not moved with the times. Nearly all HGV's now have air suspension.
 
G

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HGVs have air suspension to reduce wear on the roads, not comfort :)

Air bags are surprisingly expensive, and the systems surprisingly complex. What if a bag developed a leak?
 

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nissan nav1 said:
I can never understand why some trailer manufacturers have not introduced some kind of independent air bag suspension system on the axles
Cost.

the suspension and brakes accounts for 75-80% of trailer cost. you would probably increase the cost of the trailer by 50% or more by going to airbags (probably a lot more due to the dual axles)

most tandem axle trailers here use slipper leaf spring setup. i've only seen a couple of the rubber types. i can't see how they can make the rubber ones progressive rate. from what i've been told they don't handle big loads very well (i guess if you make them hard enough to handle big loads they will be very hard when unloaded). however the rubber ones are quiet and maintenance friendly.
 

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Discussion Starter · #20 ·
tweak'e said:
the springs counter the body movement NOT shocks. shocks are to dampen vibration out of the springs. however as shocks do tend to be pressurised they do add a bit of spring to the equation.

[quote:3zr0srep]the traielr is attched directly to the chassis, as is your ****. so you feel shocks from the trailer as if it were in the back of the nav itself.
thats exactly it.

if you want to mess with shocks it would be FAR better to add them to the trailer. dampen the vibration at the source, the trailer suspension. also have a play with the spring rates.
[/quote:3zr0srep]

Wrong.
Springs are there to support the load (body/chassis/my ****) above the axle. They need to be selected so that they have up/down movement when in use so that they can cope with holes or bumps without bottoming out or unseating.

Shock absorbers are there to damp the movement so that when there is differential movement between the two components (axle & body) the spring is not allowed to bounce forever more (undamped sin wave stylee).
The shock absorber needs to be selected to allow the two components to move sufficiently to remove bumps - any movement should be damped out after one cycle. Too stiff, and it feels like there is no suspension because the damper dominates, too soft and it will bounce up/down all the time (load dominates) - In this mode, the shock will overheat quite quickly.

So, the Navara springs are selected to handle a 1000kg load. Likewise the shocks. Unladen, they should still be in range and perfectly capable of dealing with differential movement.

By coupling a trailer on the back, you are only adding a static, vertical component of 100kg max (nose weight). Dynamically, it will be more but should still be well within the range of the suspension. (The trailer should be properly loaded obviously).

I agree with Nissan Nav1 that the lever lengths do have a strong influence, and maybe this is the problem and the dynamic range of loads on the shocks is just to high so they have moved into a position where they are load dominated.

Whatever. I will continue this debate when I have fitted the OME shocks, then the springs (with towing tests inbetween).
 
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