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The only place for a coil spring is up Zebedee's
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Joined: Jul 21 2020
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Bit of advice please.

I recently converted my recently acquired P38 from springs back to air. All went well and it drives..... well, floats along.

The air works well, does its job and keeps all 4 corners up. My concern is, are the dampers doing their job? They are the original 19 year old dampers that are not leaking.

Straight roads are fine. Rough pot holed, unmade lanes are handled brilliantly, (in my opinion compared to our RAV4 for instance). Speed humps are dispatched with ease.

The big, "BUT" is country lanes, switching right, left, right etc are awful. The car steers like a boat, it induces travel sickness in my wife who never suffers that way. I could outrun it down the lanes in a 1.2 Micra! It actually doesn't seem that safe if trying anywhere near, "pressing on".

My Mercedes ML320 is like a sports car by comparison.

Are my dampers shot? Do they all do this? Can the situation be improved? If so, what are the best ride dampers available?

Please don't say, "TADTS". Pleeese!

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Joined: Dec 30 2015
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Sounds more like a steering problem than a suspension one. It could be down to radius arm bushes, anti-roll bar bushes, any number of the bits of soggy 20 year old rubber in there.

If you fit stiffer dampers then the ride suffers (in fact, a few months after production started the dampers were made softer as very early cars were felt to be too harsh) so softer the better. It may even be down to tyres. My car feels a lot tauter than both the Ascot and the 2001 Vogue I've been working on recently. I'm on 16" wheels with higher profile tyres than the others on 18" wheels and 55 profile tyres. Both feel a bit vague but both have the same Goodyear tyres on them.

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Joined: Jul 21 2020
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Interesting. It has just had an MOT so I assume there isn’t any wear In the suspension parts.

I have just had a full set of Grabber AT3s fitted on the 18” wheels, these are standard size They have only done about 50 miles, maybe slightly more.

To be honest I don’t think the handling was any better with the road tires it had on before although these were not a name brand that I would pick!

Part of me thinks I’m being too fussy but on the other hand we are talking about a very expensive car, (at the time) and I must admit thinking about it, my same year TD5 disco with mud terrains fitted and a 2 inch lift handled better.

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You can have an enormous amount of play and it won't be picked up on the MoT. A good example being the top and bottom balljoints on the front hubs. An MoT test won't pick up any play in them as they only test for side to side movement. The way to check them is to jack it up on the axle so the wheel is dangling, then put a crowbar under the wheel and see if you can lift it. If you can, they are shot and have a very marked affect on the handling and steering. Wear in the Panhard rod bushes will allow the axle to move from side to side but again won't be picked up on the MoT.

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Joined: Jul 21 2020
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Thanks for that Gilbert. I'll put it on my lift tomorrow and check out those items.

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General tyres are made by Continental - I've got the same on the Disco and find they are fine (also 18" wheels here). Certainly handled well after doing the balljoints. Before doing them it became a bit unpredictable if you hit a pothole which way it might decide to go.

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Joined: Jul 21 2020
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Just found this interesting artical.

What's the consensus of opinion on poly bushes? I've fitted them with good results on TVRs.

https://d341lubrghrik9.cloudfront.net/documents/land-rover-world_aug13.pdf

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DON'T!!!!! They last about a fortnight if you get the soft ones and ruin the ride if you get the hard ones. They are OK on a sports car where ride is of much less importance, they were developed for racing after all, but anyone who has fitted them has found an improvement after worn out originals although nothing like as good as it should be.

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Joined: Jul 21 2020
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Hmmm, I was expecting that.. :)

What about the Billies?

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Boge were OE but are NLA so some have fitted Bilsteins and had no complaints. Problem is it's much like replacing worn out original bushes with polys. It'll be an improvement but whether it is as good as it could be is a different matter. What you don't want is anything stiffer than original so maybe something adjustable would be best.

You'll need someone who has fitted them really, I probably got the last full set of Boge when I replaced mine about 3 years ago.

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Joined: Aug 07 2019
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go out and jump up and down on the tow bar and the front bumper and see how many times you can do that before it fights back, if it trampolines the shocks are done . at 19 years old i would just tho them , the valving in side the shock would be worn beyond usefulness. i other words they are most likely stuffed

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Joined: Apr 23 2019
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My old shocks were toast after 20 years, as Mad-as says just scrap them and start again. I replaced with Monroes gas-filled, but not harsh... Check tps too - 28 psi front and 38 rear - which can make a big difference to ride. For roll, check the front anti roll bar and replace the bushes and links for starters

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Joined: Jul 21 2020
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I wonder why Superflex bushes don’t last?

I fitted these to both my TVRs, covered about 50k miles, did about 50 track days and numerous sprints.

I never had one fail.

New dampers are on the list and I will check out bushes on the ramp today. I suspect these will all be original but sound.

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Joined: Jul 21 2020
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Gilbertd wrote:

You can have an enormous amount of play and it won't be picked up on the MoT. A good example being the top and bottom balljoints on the front hubs. An MoT test won't pick up any play in them as they only test for side to side movement. The way to check them is to jack it up on the axle so the wheel is dangling, then put a crowbar under the wheel and see if you can lift it. If you can, they are shot and have a very marked affect on the handling and steering. Wear in the Panhard rod bushes will allow the axle to move from side to side but again won't be picked up on the MoT.

Checked these in the manner that you suggested and all good. Checked play in steering and all is sound there as well.

Steering doesn't actually wonder it's mainly the rolling from side to side. If you induce left right left quickly then it really does roll! Maybe a good set of dampers is what it needs.?

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Joined: Jan 16 2017
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Have you checked the height settings given you reverted it back to EAS? Others on here have calibrated using blocks of material cut to the 3 required lenghts. Morat being one of them, and fairly sure he did a write up of doing it as well.

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Good point, it will wallow around if too high.

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Joined: Jul 21 2020
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Good point.

I have got the Bearmach gizmo. Just waiting for the blue adapter for the EAS as was out of stock.

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Joined: Jul 21 2020
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Dropped the car down to the auto upholsterer this afternoon.

My wife was following behind and she said that she could see the car having a gentle jiggle and sway around!

Have had a good check of the bushes and all seem sound. After doing a lot of reading I have come to the conclusion that the Koni Heavy Track adjustable dampers would help. I shall order a set tomorrow and hopefully they should be in to me in the next couple of days in time to pick up the car from having a new headlining fitted.

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You really need to try a car with recently fitted dampers to see what the new ones you plan to get are like. I'm on recent Bilsteins so if you're close enough a try is possible. Monroe have the thumbs up from the forum too.

Wouldn't touch adjustable with a barge, let alone the pole. All they ever seem too do its to fiddle with the basic absolute rebound damping setting ignoring the velocity sensitivity. Which is a very bad thing to do on road vehicle as it upsets everything in sight. Especially a big heavy roll prone 4X4. Either, like a lot of motorcycles, the setting does nothing except amuse the owner, or you have serious risks of the suspension pumping down at speed.
If you are being ambitious off road with uprated springs and, possibly, lift tweaking the rebound will stop the suspension crashing too far, too fast downwards when you hit a hole. But you will be compromising a lot of other things which may well bite you in the ass at any sort of speed.

If you want to muck around with suspension characteristics on a road vehicle with a high centre of gravity you have to get into the shim stacks and do it all from first principles to keep things properly balanced and the natural frequency responses front and rear sensible. The odds of any ordinary person finding a better overall set-up than a decent factory are tiny. Competition guys pushing the wrong kit up to the ragged edge may think they are doing better with what is mostly a bodge fix but road car suspension operates in continuous transition regions which is much harder to achieve balance with. Serious natural frequency mismatch whether front to rear pitch, roll or (eek) diagonal is scary.

Superflex, poly bushes and the rest don't last on a P38 because roll puts considerable plunge and tilt forces into the bush. Which they aren't able to cope with. All these polybush systems are basically poor boys rose joints with a little flex over relatively short movements to handle the minor geometrical infelicities that prevent you from using proper rose joints. Fine on something like a TVR with fairly pure geometry, short movements and hard springing to keep movements pretty close to the proper geometry range.

A P38 has long link / radius arms both ends with the axles well located on the arms so the geometry is anything but pure. Long travels too. When it rolls either the bushes have to take up serious plunge and tilt force or the arms and axle have to twist and bend. The glass fibre arms at the rear do twist and bend. If you look back into the history of the GKN glass fibre leaf spring and suspension arm design its precisely what they were developed to do.
Good luck on twisting the front radius arms. The axle to arm bushes have to handle it all. A rose jointed P38 front suspension is pretty much locked solid. Despite its apparent simplicity its actually a very sophisticated design.
Big, fast, 4 x 4 suspension is hard to do. Which is why most of the more modern incarnations with apparently more up to date designs fall apart with monotonous regularity over any sort of mileage.

Clive

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Joined: Jul 21 2020
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Clive, a good post. Lots to think about.

Obviously, I am just taking other peoples views from the Internet.

Whereabouts are you? I am near Dorking in Surrey.