Technical Question re D3/4/RRS Air Suspension

One of the caravan mags did a test with a D3 on a weight bridge.

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"When a van with a ballweight of 160 kgs was connected, the front end weight went from 1240 to 1180 - a drop of 60 kilos, or only 4%. There was no noticeable difference in the feel of the steering."

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Originally Posted by Rockylizard

I was just wondering, given the safety advantages of WDH, which I have towed with previously on other vehicles,

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Maybe it should be said as "perceived" safety advantages :angel:

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Originally Posted by Graeme

Something that's often overlooked is that ABS allows rear wheels to do a lot more of the braking when the rear is loaded. Usually too much weight is transferred to the front wheels especially if the vehicle nose-dives, so having less weight on the front wheels doesn't necessarily mean less braking ability.

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Plain ABS won't do that for you, as all it does is stop a rear wheel locking. What will help is EBD which will distribute brakeforce to the rear, in effect changing the brake bias instantly. Because of the extra weight you'll get more braking, but...because of the extra weight you'll need it!

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Originally Posted by mowog

One of the caravan mags did a test with a D3 on a weight bridge.

Quote.

"When a van with a ballweight of 160 kgs was connected, the front end weight went from 1240 to 1180 - a drop of 60 kilos, or only 4%. There was no noticeable difference in the feel of the steering."

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exactly. pretty simple physics, measure distance from centre of rear wheels to towball, multiply by towball mass, then measure wheelbase and resolve to find the equivalent force to balance. Not a whole lot.

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Originally Posted by gps-au

Maybe it should be said as "perceived" safety advantages :angel:

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A WDH is definitely an advantage for many vehicles and indeed required for many at certain weights, so the advantage is very much more than perceived. As described the Disco's EAS keep the car level, and the reduction in weight off the front is negligble. For a lighter, softer-sprung car with a shorter wheelbase and greater rear overhang it becomes more important. This is why you need larger 4WDs to safely tow 3500kg.

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Originally Posted by rmp

Plain ABS won't do that for you, as all it does is stop a rear wheel locking. What will help is EBD which will distribute brakeforce to the rear, in effect changing the brake bias instantly. Because of the extra weight you'll get more braking, but...because of the extra weight you'll need it!

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Yeah, I took a shortcut and didn't explain what can be done with ABS.

This is why I recently purchased a D3 to be able to tow our off road caravan without a WDH.

I take the van quite a bit of road and a WDH is a real pain in the backside off road.
I can see why most people swear by WDH's as most vehicles are pretty useless at towing so the WDH hides most of the weight balance problems. I spent the last two days towing the van around with the D2a while I get all the gear I want fitted to the D3 before I tow the van with it.

Over the last six months in most cases towing with the D2a has been quite good, I think this is the case especially because of the ACE which helps with body roll and handling. Though even with the standard air suspension on the rear it still sags and makes the front end light, add in heavy braking on dirt roads and it can become quite dangerous on occassion as the front locks up and then doesn't steer.

This happems with a ball weight of just over 200 kg depending on what is in the front boot of the van, I really wouldn't like to drive it with the D2a's maximum 250 kg ball weight on bumpy twisty dirt roads.

So rather then fit a WDH which would have helped considerably how the D2a rides and steers with a Van on the back I just brought the D3. Hopefully this will improve the driving safety levels aswell as comfort levels and more important then comfort the ability to go up steep hills at more then bloody 40 kph which often happened with the D2a.

cheers,
Terry