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Hi,
I'm towing a 1700kg caravan and notice that it depresses the rear quite a bit even when moving stuff around in the caravan. Has anyone any experience/ ideas with stiffening or boosting the rear springs? I'm leaning towards an insert between the springs at this stage.
 

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Unidexter,
Your cars suspension lowering would suggest non air suspension?So I presume steel springs?
Other then replacing your springs with graduated springs (more weight ,progressively less travel) or air bags assistance (manually adjusted),your insert suggestions may do little to help.
Our previous caravan towing vehicles was 2011 AWD diesel Ford Territory firstly updated the springs followed by air bag assistance.
Air bags did the trick extremely effectively,was roughly $500 all up though.
Air suspension is pure heaven!

Weight distribution is critical for safety towing heavy vans,ours is not of excessive weight however,2500kg is still a significant weight swinging off the towball.
Stick to 10% towball weight together with electronic stability control, it’s wonderful!
Cheers,
Mick.
 

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Hi,
I'm towing a 1700kg caravan and notice that it depresses the rear quite a bit even when moving stuff around in the caravan. Has anyone any experience/ ideas with stiffening or boosting the rear springs? I'm leaning towards an insert between the springs at this stage.
Well, this depends on the rear axle load limit. A weight distribution hitch (WDH) has an advantage here. Stiffer springs (even air suspension) does not.

I know that for a air suspension tregs WDH is not "allowed" although many use them. A WDH will fix your issue as I assume you have a steel suspension model. It also may not be "allowed" though. Your decision.

So what is a WDH doing?

Many do not realise (even care?) that axle loading in the rear can severely restrict the payload you can carry in the vehicle once the trailer is connected. So the other consideration for WDH is rear axle loading not just the levelling action.

What is happening when you use WDH is that some of the ball load is moved to the front axle giving you more payload capacity in the rear of the vehicle. If you can picture it, the WDH system is using the trailer mass as leverage and lifts the ball, the effect rotates the vehicle on the rear axle pushing the front of the vehicle down and lifting the rear. This action is basic lever arm based. The distance from the ball to the rear axle is one lever arm and the distance between the axles another. The distances axle to axle and axle to ball can be used calculate the effect given say a 120 WDH (200kg WDH also possible). Assuming your axle limits are 1370kg front and 1520 rear ( I think correct for a 180TDI) , with a 1700 ATM trailer connected with 10% ball load, for a 180TDI you will only have 180kg left before you exceed the load rating of the rear axle, 80kg for a 150TDI. For a 150TDI this might be an issue. The front axle will have in reserve 340kg for the 150 TDI and 440kg for the 180TDI. Applying a 120 kg WDH this changes to headroom of 390 front and 260 for the rear for the 180TDI and for the 150TDI 300 front and 160 rear. These numbers will not be accurate - I do not have the axles spacing for the Tregs - but I mention these numbers to show the effect. If you have the axle maximum loading and axle spacing and axle to ball spacing you can enter the numbers here and play yourself.


The air suspension tregs hide the fact that rear axles is absorbing most of the ball load with a corresponding impact on the vehicle payload possible. Adding stiffer springs to the rear will do the same thing - hide what is happening re axle loading.
 
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