MY12 D4 suspension stiffness (lack thereof)

[Brad]

I picked up my new MY12 Disco 4 SE in Nara Bronze last Friday and so far the permagrin is yet to wear off :) One item which is starting to bug me however is how apparently soft the suspension is.

Driving on normal condition Sydney roads many small bumps will set off oscillations which repeat up to two times before damping out. For example left side compress, right side compress, left side compress, right side compress, damped. Is this normal for D4? I don't recall similar softness in vehicles I've test driven however the last time I drove one was probably 6 months ago and it was not MY12.

I had a '93 D1 prior to this which exhibited similar (but slightly more pronounced) behavior, which I attributed to worn shock absorbers. Putting Bilsteins in greatly stiffened (and improved IMHO) the ride.

Should I be asking the dealer to examine the car or is this the default setup? If the latter, is my only option to have the shock absorbers replaced with something better?

[Redback]

Are we saying the car bounces and wallows, if so it shouldn't, the D4 has a stiffer suspension than the D3 and is quite stable.

Baz.

[Disco4SE]

Something strange going on Brad.
As Baz mentioned, the D4 suspension is firmer than the D3. If anything, there has been comments on the D4 being stiffer in the suspension, but definately not soft??

I'd take it back to the stealers and let them drive it.

Cheers, Craig

[Celtoid]

He Brad,

There is a little wallow in my 3.0l D4 but it's minimal compared to other 4WDs I've driven, and surprisingly slight for such a heavy truck.

I've also read on this forum that the D4 shocks are rated as being pretty good, and same for same replacement would be advised in the event of new ones being needed.

Cheers,

Kev.

[CaverD3]

D4 is definately stiffer than the D3. Are your balls hanging free or have they got caught up somewhere?

[jonesy63]

D4 is definately stiffer than the D3. Are your balls hanging free or have they got caught up somewhere?

Gee Caver - getting a bit personal now, aren't we? :wasntme:

[CaverD3]

Twas me!;)

D4s not his. :D

[Brad]

It definitely feels "not right", to the point that I have had several passengers seperately complain about it.

Booked into Parramatta Trivett tomorrow so we will see how it goes.

[Brad]

Are your balls hanging free or have they got caught up somewhere?

I am vaguely aware of what these are - could you enlighten me as to their relevence to suspension?

[CaverD3]

Harmonic damper at the back. Large cast wieghts and can make an enormous difference to the ride if they are not free. Sometimes get hung up on wiring. Could be the cause of the not quite right ride.

[Graeme]

Could it be just the front wheels then the rear wheels going over a bump? I recall that I initially noticed the rear-end moving about rather strangely over bumps after having driven live axle LRs for many years.

[Brad]

Could it be just the front wheels then the rear wheels going over a bump? I recall that I initially noticed the rear-end moving about rather strangely over bumps after having driven live axle LRs for many years.

It's mostly side to side oscillation but there's an element of front to back also. Basically it behaves like my D1 with worn shocks, but maybe 10% less wallow. At times almost like being at in a small boat crossing the wake of a bigger one.

[Celtoid]

It's mostly side to side oscillation but there's an element of front to back also. Basically it behaves like my D1 with worn shocks, but maybe 10% less wallow. At times almost like being at in a small boat crossing the wake of a bigger one.

That doesn't sound right at all.

[Brad]

Took a Trivett Service staff member on a five minute drive around Parramatta. He was of the opinion that the suspension was normal. He did however offer to leave it with them and they would examine a few items. I am supposed to pick it up at 4pm this afternoon.

*Edit* Have now picked up the vehicle and dealer says it's normal. I'll tee up a test drive to compare it against at the dealer next week. If it turns out the ride is the same then maybe the fault lies with me.

[Brad]

tl;dr: Air suspension is significantly stiffer in access height. Access height body roll is excessive due to this. Normal height is fine. My vehicle behaves same as demo vehicle.

I drove a 3.0 (unsure whether SE or HSE) on Friday at the dealership back to back with mine, with a friend and a sales guy along for their opinions. Long story short the ride was almost exactly the same at normal height between both vehicles.

I managed to replicate the bouncing only while in access height going over speed bumps at about 10km/hr. I did not this on the demo vehicle however I'm confident the behavior would be the same.

A friend explained it this way:

1. Shock absorber has a maximum amount of damping it can provide (measured in Newtons). Call it 'Y' newtons.
2. A given spring (or in this case, air suspension at a given setting) will provide a maximum of 'X' force against compression (body roll). This force will be released after maximum compression, to be damped by the shock absorber.
3. If 'Z' is greater than 0 in the equation 'x-y=z', there will be excess force not damped which will translate into a body roll onto the opposite side of the car (where the same process repeats).

Given the above, we assumed that the "stiffness" of the air suspension ( how high 'X' is ) is significantly more in access height than in normal height.

Moving over the same speed bump at 10km/hr at an angle, in normal mode vs access mode, we saw one compress-rebound cycle per wheel in normal height mode vs two per wheel in access mode.

[Graeme]

10 kph at access height over a speed bump may have had the front shocks bouncing off their bump stops. The bump stops compress significantly, unlike the normal external bump-stops.

[PaulGOz]

I have found access height to be very harsh over speed humps much worse than many sports cars I have owned. It will bounce like mad in access height over speed humps and bumps. I have put this down to insufficient travel I believe the front is worse. I now only use access height for vehicle loading and unloading and when I know I am at risk of using the roof racks as a can opener. The only gripe I had with the suspension when I first got it was I though the dampening could have been a bit stiffer when fully loaded, I have since forgotten about this but hope that the D5 will come with both air suspension and those electromagnetic shocks then I will have another knob in the car. :p