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Discussion Starter #1
Hi people,

I have a manual D40 and I tow quite freqently, mainly twin axle plant trailers with diggers etc.
My problem is even with a twin axel trailer taking most of the weight I seem to get quite alot of rear end suspension sag, what are people installing to counter this?

Many thanks.

Mike.
 

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Hi people,

I have a manual D40 and I tow quite freqently, mainly twin axle plant trailers with diggers etc.
My problem is even with a twin axel trailer taking most of the weight I seem to get quite alot of rear end suspension sag, what are people installing to counter this?

Many thanks.

Mike.
Welcome to the forum.

You shouldn't get sag with a twin axle trailer if you balanced the load with about 100kg load on the towbar.

If you want to beef up the rear springs you have a few options.
  • New heavy duty springs
  • Helper spring
  • Air helper spring
Air is more expensive, but can be adjusted via an on board compressor or an airline.
 

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Discussion Starter #3
The problem with towing a plant trailer with a mini digger on is there isn't alot of room for perfect placement for weight distribution as they're quite compact trailers.
We also have a large flat deck trailer and that's much easier to distribute weight over.
My brother in law has the dunlop air system on his truck and that does work well but it's very expensive.
Does a helper spring replace the damper?
 

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No, a helper spring just bolts to the existing spring.

Oddly, replacing the springs is the cheapest option.

There are kits around for much less than the Dunlop kit, can't see one for a Navara, but here is one for an Isuzu at less than £300. Rear Leaf Spring Air Bag Assistance Kit for Isuzu Rodeo 4x4 3.0TD 7/2003-8/2006 | eBay

The other option is extended shackles which will lift the back end an inch or so, but proabably not what you want.
 

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Hi people,

I have a manual D40 and I tow quite freqently, mainly twin axle plant trailers with diggers etc.
My problem is even with a twin axel trailer taking most of the weight I seem to get quite alot of rear end suspension sag, what are people installing to counter this?

Many thanks.

Mike.
Sounds like you have far to much nose weight on the trailer far in excess of the design weight of the tow bar and the chassis and we all know how that could be compromised. . Not trying to teach anybody to suck eggs but are you loading the digger the right way around as it makes a huge difference to distribution and nose weight.
 

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Heavy duty springs and an adjustable hitch for twin/triple axle trailers. Something like THESE. Provided you tend to load the tub too. If not, just (fresh) medium duty springs and an adjustable hitch. All done for under five hundred notes.

Not sure how old your existing springs are, or the exact makeup of your trailer.
 

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Discussion Starter #7
Sounds like you have far to much nose weight on the trailer far in excess of the design weight of the tow bar and the chassis and we all know how that could be compromised. . Not trying to teach anybody to suck eggs but are you loading the digger the right way around as it makes a huge difference to distribution and nose weight.
All loaded correctly yeh, my boss has a new ranger and when loaded exactly as the trailer is on mine the ranger doesnt sag at all.

I think my springs are just on the way out and need replacing
 

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Discussion Starter #8
Heavy duty springs and an adjustable hitch for twin/triple axle trailers. Something like THESE. Provided you tend to load the tub too. If not, just (fresh) medium duty springs and an adjustable hitch. All done for under five hundred notes.

Not sure how old your existing springs are, or the exact makeup of your trailer.
Brilliant, thanks for that, those heavy duty springs look just the job!
 

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Sorry to say I disagree with some of the advice above re “the trailer must be too heavy”. Even 100kg on the ball will result in substantial suspension sag on the Navara, like all pick-ups - the ball is just so far behind the axle!

This is a common fault in Oz where heavy towing loads are normal. The number of axles on the trailer makes no difference at all to how much weight should be borne by the tow vehicle, it’s more to do with the weight bearing capacity of the trailer itself. The only exception would be if you moved the two axles to the front and rear of the trailer with the front set being steerable - what is known as a dog trailer - but this is the stuff of multi combination heavy vehicles and requires specialist towing equipment.

Your best options to reduce it (you can never eliminate it, suspension is designed to move when force is applied!) are:

1. Heavier duty rear springs (best option)
2. Airbags between the spring and chassis (has some risks)
3. A combination of the two (ie slightly heavier springs so the airbag does less of the work)

If you’re regularly towing, you should invest in heavier-duty rear springs to match your regular rear axle weight. And he cautious you are not overloading the vehicle - Nissan require you to reduce the maximum payload of the vehicle by a factor above the weight applied to the ball.
 

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Discussion Starter #10
Sorry to say I disagree with some of the advice above re “the trailer must be too heavy”. Even 100kg on the ball will result in substantial suspension sag on the Navara, like all pick-ups - the ball is just so far behind the axle!

This is a common fault in Oz where heavy towing loads are normal. The number of axles on the trailer makes no difference at all to how much weight should be borne by the tow vehicle, it’s more to do with the weight bearing capacity of the trailer itself. The only exception would be if you moved the two axles to the front and rear of the trailer with the front set being steerable - what is known as a dog trailer - but this is the stuff of multi combination heavy vehicles and requires specialist towing equipment.

Your best options to reduce it (you can never eliminate it, suspension is designed to move when force is applied!) are:

1. Heavier duty rear springs (best option)
2. Airbags between the spring and chassis (has some risks)
3. A combination of the two (ie slightly heavier springs so the airbag does less of the work)

If you’re regularly towing, you should invest in heavier-duty rear springs to match your regular rear axle weight. And he cautious you are not overloading the vehicle - Nissan require you to reduce the maximum payload of the vehicle by a factor above the weight applied to the ball.
Thankyou for that, very informative!
I'll be investing in some heavy duty springs and hopefully that will make a difference! If not I'll have to try some airbags aswell.
 
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