The Discovery 4 is a second rate tow vehicle

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Originally Posted by brad72

Would i be wrong in saying that a WDH mearly (used as a loose term) bandaids wrong suspension type, badly loaded car or incorrect tongue weight that is outside the vehicle manufacturers specs?

But is saying that not many of us have access to a nose weight indicator to ensure everthing is loaded correctly every time we change something to ensure correct driving charateristics.

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Yep I think you are wrong.

Not sure what all the concern is here as a D4 is a whole lot different to a Prado on coils with supplementary coilrite in spring air bags. I doubt too may in the caravan post know anything of D4 suspensions and would not be having their discussion with a D4 suspension in mind. That prado should have a WDH with anything other than a very light van but a D4 (with 4 post electronic air bags) should not, end of story. True the D4 can not lever weight onto the front but it will be good enough so long as the driver understands the limitations of the rig. And before anyone gets sensitive about the use of the word "limitations" in a D4 post, all rigs have limitations. It just happens that a limitation of a D4 suspension is that it does not suit a WDH.

Maybe what we really need is for a D4 owner to sit his front wheels on a wieght bridge and hitch/unhitch a van and see for sure without guess work what the load is on the front wheels. Pat

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Originally Posted by PAT303

Maybe what we really need is for a D4 owner to sit his front wheels on a wieght bridge and hitch/unhitch a van and see for sure without guess work what the load is on the front wheels. Pat

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When I get a chance I will do this.

I need to see what our van weighs now that it is setup in full trip mode.

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Originally Posted by John W

Yep I think you are wrong.

Not sure what all the concern is here as a D4 is a whole lot different to a Prado on coils with supplementary coilrite in spring air bags. I doubt too may in the caravan post know anything of D4 suspensions and would not be having their discussion with a D4 suspension in mind.

That prado should have a WDH with anything other than a very light van but a D4 (with 4 post electronic air bags) should not, end of story. True the D4 can not lever weight onto the front but it will be good enough so long as the driver understands the limitations of the rig. And before anyone gets sensitive about the use of the word "limitations" in a D4 post, all rigs have limitations. It just happens that a limitation of a D4 suspension is that it does not suit a WDH.

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In actual fact these people on the other sites are spending quite a bit of time bagging D3/4's suspension as being rubbish and badly designed because it doesn't use a WDH. But they are also comparing D3/4's as being 'lightweight tow vehicles' unlike Patrols and Crusiers which they consider as heavyweight tow vehicles. The big joke is most diesel Patrols are auto's so can only tow legally 2.5 ton, yet they often decide to ignore this fact.

Is it a limitation for D3/4 not to have a WDH? I would say it was if the suspension isn't designed properly and the vehicle operated better with one, but there is nothing to show that this is the case. So if that is the case then it is not a limitation.

cheers,
Terry

Pat303 asked for some figures, and I just happen to have some available. Hope they suffice?
New D4, with full fuel, and driver weight at 80Kgs, I put the vehicle on our local Weighbridge. Axle figures were:-
Front_ _ _1.320.
Rear_ _ _ 1.340.
This gives a Kerb Weight of 2.660, which is 77 kgs over the book of 2.583, don't know why this was so?
We are presently approaching the end of our first trip, and with a heavy Caravan hitched up. and at the beginning, I put the whole rig, all loaded up, on the Weighbridge again. These are the figures, but now the car has the addition of, ARB steel Bull Bar, LR Cargo Barrier, Floor mats, 3" S/Steel side tubes, 18" Rims.

GCM 6.10. ie; GVM + ATM.
GTM 2.90 this is discounting the Ball Weight.
ATM 3.20 this is total mass, including Ball Weight.
Ball Weight .30.
D4 GVM, unhitched, 2.90.
D4 hitched, including ball weight 3.20.
Front Axle 1.26.
Rear Axle 1.94.
Although the D4 was 40 kgs below limit, hitched up, the rear axle was over the top by 85 kgs, so I had to make a few changes to loading before proceeding further.
All in all, these figures have given me 'Food for Thought' regarding safe, and legal loading of the 'Combination'. Maybe I should not carry the 60 Lts of Diesel on the drawbar. This would reduce Ball Weight, which would take a bit off the vehicle, and also the Caravan.
Interesting to note that, although the Bull Bar is supposed to add 35 kgs to front axle and with my 60 kgs wife, plus cargo on the rear seats, adding a slight bit to front loading, that the 300 kgs Ball Weight lifts 60 kgs off the front loading.
Pick through these figures Guys, somebody else's slant would be appreciated.
Don.

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Originally Posted by TerryO

In actual fact these people on the other sites are spending quite a bit of time bagging D3/4's suspension as being rubbish and badly designed because it doesn't use a WDH. But they are also comparing D3/4's as being 'lightweight tow vehicles' unlike Patrols and Crusiers which they consider as heavyweight tow vehicles. The big joke is most diesel Patrols are auto's so can only tow legally 2.5 ton, yet they often decide to ignore this fact.

Is it a limitation for D3/4 not to have a WDH? I would say it was if the suspension isn't designed properly and the vehicle operated better with one, but there is nothing to show that this is the case. So if that is the case then it is not a limitation.

cheers,
Terry

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Thanks Terry I admit that I did not read more than the first couple of pages of the posts. If they are bagging the D4 then they are fools. I would still argue though that if the electronic controlled D4 suspension could handle a WDH then it would be an added advantage but that does not take anything away from the fact that a D4 is more than adequate with a big van.

Thanks Don. Excellent post mate.

So it's settled then that auto controlled bags still allow substantial weight to come off the front wheels (with negative effects on braking in particular) and only a wDh (if it could be used in this case) would be able to lever the weight back onto the front?

Perhaps the caravan forum blokes when talking about the cruiser being a heavyweight tower were talking of them cruisers weight - more the merrier. The kerb weight on any of these big wagons is not an issue at lower levels but at over 3k say every bit of extra kg of the tow vehicle is a good thing.



Cheers

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Originally Posted by ozscott

Thanks Don. Excellent post mate.

So it's settled then that auto controlled bags still allow substantial weight to come off the front wheels (with negative effects on braking in particular) and only a wDh (if it could be used in this case) would be able to lever the weight back onto the front?

Perhaps the caravan forum blokes when talking about the cruiser being a heavyweight tower were talking of them cruisers weight - more the merrier. The kerb weight on any of these big wagons is not an issue at lower levels but at over 3k say every bit of extra kg of the tow vehicle is a good thing.





Cheers

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Personnally I'm not convinced a WDH will put weight back onto the front axle as much as they are reported too, There is still all that weight over the back axle..

Would be interested to see (as an excample only) a WDH attached to the D4 above and the same test preformed again, that would convince me once and for all.

Or a comparitive test using a different vehicle.

Anyone got a WDH they can lend:D

Baz.

That would give a definitive answer as to wether a WDH did lever weight forward,if it did it'll be a know brainer as to why they rip towbars off. Pat

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Originally Posted by Redback

Would be interested to see (as an excample only) a WDH attached to the D4 above and the same test preformed again, that would convince me once and for all.

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A 4WD mag some time ago did a tow test with several vehicles. They fitted a WDH to each vehicle including a D3, although they had to play around with the D3's adjustment to get the setup to ride properly and not compete with the air suspension. I suspect the WDH provided only a small transfer from the rear wheels because of conflicts with the air suspension's levelling if too much weight was tried to be lifted off the rear. The tow test was not repeated without a WDH because the assumption was that it was best to have a WDH fitted.

A WDH on the D4 could interfere with trailer stability assist's ability to detect and correct sway, along with the usual disadvantage when travelling over ruts and affecting ride height thus could compete with the supension's desire to self-level. The minimal weight transfer from the front even with the maximum ball weight is a small enough percentage of the D3/4's front axle weight that I'd expect it to be inconsequental. The air suspension will keep the vehicle at its normal ride height all round and the suspension geometry will therefore be normal, unlike vehicles with steel springs.