D4 suspension

[landoman]

My 2011 D4 recently had developed very poor ride quality at 50 K ...a very harse ride with every bump transmitting through the car and steering wheel ...and the car rocking around like a luna park ride .....most unpleasent
The remedy was to replace all 4 shocks .....but the ride was still not as smooth as it previously had been when the vechicle was new

After driving about 3 weeks with my new shocks and the ride still a little too firm I one day turned OFF the dynamic stability control and then turned it on again ....and low and behold it seemed to improve the ride quality .....Im sure i am not imagining this ???? . Can anyone out there who has some understanding of the suspension mechanics of D4 explain why this might be ......(did I RESET something ) .......as suspension and shocks are beyond my simple nonmechanical mind .

Also does the air suspension its self loose some of it effectiveness over time

I am also thinking with the Tyre pressures at the 40 psi reccomended by the fitter ( Cooper zenons ) may be contributing to the harsher ride. I know when the pressure in the Zenons is low they bag a bit ...perhaps thats why the suppliers reccomend 40 psi ....my OEM Wranglers were as per door plate at 33 front 36 back so Im thinking of putting my coopers back to that setting

Any and all comments welcome

[Graeme]

Why not drop the tyres to the LR recommended pressures? Its easy enough to pump them back up a bit if too soft. As little as 2 psi difference can make a significant difference in ride.

[jon3950]

Are we talking 19"s? I think 40psi is just way too high for the fronts and a bit high for the rear too unless carrying a load.

As Graeme suggested try starting with the placard pressures and going up from there. I'm running 34 front & 38 rear unladen on the bitumen with my Zeons and the ride is excellent.

Cheers,
Jon

[discojools]

Definitely let the pressures down to manufacturers settings unless you have a bar and winch in which case inflate the front to around 35. Nearly all the tyre fitters i have used have told me and set tyres at over 40psi. I personally think it is potentially dangerous advice. I ( and other friends of mine) have had close calls with lack of grip associated with too high pressures. Also spoils the ride quality.
I have no idea why the fitters give this advice. Some say it gives better economy. No good if you can't stay on the road. I firmly believe that it contributes to our inflated (no pun intended!) accident rate in this country.
I know that while I lived in the UK tyre fitters always had a a table of all makes and models and their associated recommended tyre pressures. I'm not sure if this was a legal requirement or not but it meant that all vehicles left the workshop with the correct pressures. Here it seems that 45 psi is the default pressure.
As a side note I have noticed that since I fitted my winch and bar the ride especially at the front has degraded a little bit. Also I see no problem with radial tyres bagging a bit.

[landoman]

ok guys ......thanks for the advice ....i will take the pressures down to the levels reccomended on the door plates and see what that does

also ....does anyone know if airsuspension deteriorates over time .....or is it the shocks that absorb the bumps ....so what does the air suspension do ...does it help absorb road shocks or does it just keep the car level on the road

sorry these may seem silly questions .....but i have no mechanical knoweledge what so ever

[jon3950]

Effectively, the air suspension is doing the same job as a coil spring. It uses the compression of air instead of the torsion in a steel wire to act as the springing medium.

In a suspension system, the spring (in this case the air bag) absorbs the bump and the shock absorber (or more correctly, damper) controls the movement.

The air suspension itself doesn't deteriorate. Essentially, as long as the bag hasn't split it is working. It can leak, but I don't think this is relevant to what you are experiencing. The shocks will of course deteriorate, as you have experienced. In the Disco, the shock and air bag are in one integral unit, similar in principle to a McPherson strut.

All a bit of a simplification, but hope it helps.

Cheers,
Jon

[landoman]

Effectively, the air suspension is doing the same job as a coil spring. It uses the compression of air instead of the torsion in a steel wire to act as the springing medium.

In a suspension system, the spring (in this case the air bag) absorbs the bump and the shock absorber (or more correctly, damper) controls the movement.

The air suspension itself doesn't deteriorate. Essentially, as long as the bag hasn't split it is working. It can leak, but I don't think this is relevant to what you are experiencing. The shocks will of course deteriorate, as you have experienced. In the Disco, the shock and air bag are in one integral unit, similar in principle to a McPherson strut.

All a bit of a simplification, but hope it helps.

Cheers,
Jon

Thanks Jon ......ok so if the shocks and bags are an integral unit ....does that mean that when the shocks were replaced I got new bags as well ........

..if the shocks (dampers) control the movement and the airbags (suspension) controlls the bumps ....then any bumps are to do with the airbags ......or the tyre pressures .................right .????......

This is starting to make sense to my unmechanical mind !!

[gghaggis]

You can change the dampers independently of the air-bags (although of course, you still have to remove the entire strut assembly and break them apart). Many people don't bother and just replace the whole assembly, but you don't have to.

Simplistically, the bags "absorb" the bumps, the dampers "dampen" any rebound/oscillations.

Cheers,

Gordon

[landoman]

You can change the dampers independently of the air-bags (although of course, you still have to remove the entire strut assembly and break them apart). Many people don't bother and just replace the whole assembly, but you don't have to.

Simplistically, the bags "absorb" the bumps, the dampers "dampen" any rebound/oscillations.

Cheers,

Gordon


oK so if I'm getting bumps in the ride then its the air bags not the shocks (dampers ) that would be the reason

so do these airbags deteriorate with age or vigerous use (like a good run over corregations ) .......
I think only the shocks (dampers) were replaced ....not the bags .....could the bags have deteriorated and so the " bumps are getting bigger " (apologies to Elvis Costello !!)

[pwillo]

My D4 is still on the boat, but I have need stalking AULRO & Disco 3 UK for a while.
Plans are to replace the 19" factory rubber on day 2 with Zeons.

Has anyone tried the 4 psi rule on the Zeons to find a good pressure?

Regards

[LGM]

My 2011 D4 came with Continental Tyres and the ride was quite plush to me. I replaced those tyres at 32000k and fitted Zeon LTZ's. I run the Zeon's at the door plate pressure or thereabouts and have now done a total of 65000k.

In fact on checking I have 32F and 36R pressure in the tyres at the moment.

The ride is as good as it was with the Continentals but there is a little more road noise due to the tread pattern. I rotate the tyres (5 way rotation) each 10000k and so far the wear is even all around. Looks like they will go close to double the wear of the Continentals.:D

I have not noticed any appreciable variation in the ride quality and as above the vehicle has done 65000k. Equally I don't think the shockies are on the way out (as far as I can tell).

Sometimes when I read these threads I begin to wonder if I am missing something when I check out my vehicle???

Maybe I have a screw loose:p

[Celtoid]

Hi,

I've found tyre pressure makes a big difference to ride quality but you have to be careful when you change brands/types.

I switched my OEM Wranglers over to Scorpion ATRs and got them at the usual tyre shop 'recommended' rock hard, over 40PSI setting. I found them harsh and a little skittish in the wet (although I've been told increased pressure in the wet actually helps with traction....that may depend on just how much of an increase). I dropped to the placard 33 + 36, with a much improved ride.

Problem with this didn't become apparent for a little while though. I have effectively reduced the life of my Scorpions as they all wore (all 4) on the outside edges quicker than the inside. Which is indicative of pressures being too low.

I had to pick the best of the worst for the back and spare, buy one new one and employ the spare tyre (never used), so that I had two good tyres on the front. I'm now operating just below 40PSI in the front and above in the rear (so that I get some more use of the middle, where the tread is still good).

I'll have to monitor wear much more closely now.

You'd hope manufacturers would be able to supply the correct data...but I guess there are lots of variables...weight of vehicle, usage, power, etc.

I face the same dilemma with the new 18" Zeon LTZs I just bought as I don't know what pressure to run those on the road at....came from tyre place at 42PSI.

Anyway, as other have suggested, play with the pressures until you get a good ride. If the corresponding pressures are at placard or above, it was your tyres. If not (as in the pressure is lower), I'd be taking the car back.

And as I've learned the hard way...watch wear carefully.....it's a bloody expensive mistake on 19" tyres. :mad:

Cheers,

Kev.

[phl]

The tyre place must have been hedging their bets when they installed my Zeons. According to my tyre pressure gauge, they were at 40FL, 39FR, 36RL, 37RR.

Took them up to 40 all around, and haven't noticed any harshness in ride. Mind you, it felt absolutely plush after test driving the IS300h with run flat tyres; I now remember why we didn't get a 3 series previously.

[landoman]

My D4 is still on the boat, but I have need stalking AULRO & Disco 3 UK for a while.
Plans are to replace the 19" factory rubber on day 2 with Zeons.

Has anyone tried the 4 psi rule on the Zeons to find a good pressure?

Regards


what is the 4psi rule ??

[SBD4]

what is the 4psi rule ??

There's quite a bit of info available on it but have a read of this to get an idea:

Using the 4psi Tyre Inflation Rule @ ExplorOz Blogs (http://www.exploroz.com/Members/216531.875/2/2012/Using_the_4psi_Tyre_Inflation_Rule.aspx)

[pwillo]

Probably more correctly should be referred to as a guide rather than a rule.

It takes into account the differing loaded state of a tyre and suggests that a tyre at the correct pressure for the load should, when in use, increase by 4 psi.

This of course doesn't take into account ambient temperature and changes barometric pressure.

It does however seem reasonable that generally it would be a useful guide.

Regards