Dampers/shock absorbers for XJS V12

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skodajag
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Dampers/shock absorbers for XJS V12

Postby skodajag » Tue Aug 28, 2018 9:03 pm

It's time to replace the shock absorbers on my 1988 XJS V12. I want to preserve the magic carpet ride rather than fast/ flat cornering. What do you suggest?

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Wed Aug 29, 2018 8:12 am

Front or rear? Have a look at other messages in the suspension section for ideas, I fitted adjustable Spax units on the front a while ago and they work well at a reasonable price.
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

davidr
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Re: Dampers/shock absorbers for XJS V12

Postby davidr » Wed Aug 29, 2018 8:56 am

Original rear dampers are still available from Jaguar and OE spec front ones from the likes of DMG and SNGB.
What many people do is fit ones with adjustable damping rates like the Spax Pop mentioned. This gives you the opportunity to dial in the feel you want.
Adjustable length rear dampers are also a useful thing as this allows you to compensate for the springs sagging a bit. Keeping your original springs is important as they are no longer available from Jaguar and although aftermarket alternatives are available my experience is that they are of very variable quality and I found that I couldn't get the feel I wanted so used refurbished original ones on my 1989 V12 to keep the "magic carpet".
XJS FORUM COORDINATOR
1996 XJS Celebration Conv. (shown on the JEC stand at NEC Nov 2015)
2001 XKR Convertible

Previously enjoyed!
1989 XJ-S V12 Coupe. 2006 XJ TDVi Sovereign. 1995 XJ6 3.2. 2013 XF 2.2d. 2009 X Type 2.0d Sovereign estate

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Sat Oct 13, 2018 5:50 pm

Is there any way of ascertaining if the rear dampers need changing?

From my records one damper was changed over 20 years ago before I bought the car and I suspect the rest are originals. Time would suggest that a change can only be a good thing but well, cost etc.

Bouncing the car up and down doesn't prove much apart from the squeeking noises from my hips and back. As there are 2 dampers each side a good one could hide a bad 'un.

None are weeping, but I think over the winter i will remove them and seperate the springs and see if I can form an opinion.
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

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ng4xjs
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Re: Dampers/shock absorbers for XJS V12

Postby ng4xjs » Mon Oct 15, 2018 7:30 pm

I think that's the clue, when they start to weep. I guess all mine probably need doing. Like Pop maybe this Winter.

Nick
1994 4.0 XJS AJ16 BRG
2006 2.5 V6 AWD XType Silver

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Tue Oct 30, 2018 11:46 am

I removed the rear dampers for inspection and I'm glad I did. The top bushes had deteriated badly.
bush failed.jpg
Only one shock could be dismantled, the collets on the others were completely siezed, no amount of plus gas, heat or hammering would release them. Out with the angle grinder with a 1mm cutting disc and they were apart.

As you will see in the photo, one shock is a different pattern to the others and had lost all damping, no springiness left in it at all. Interestingly there was no oil leakage at all, the wetness in the photo was from all the releasing fluid I had used to remove the collets.
dampers old.jpg
Todays task is to clean and paint the springs and to order a new set of dampers.
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Fri Nov 02, 2018 12:45 pm

I cleaned the springs up, painted with black smooth Hammerite and attached new dampers. I chose Spax as I have that make on the front already, there are numerous other makes available so others might prefer a different setup. The collet system is far easier to use on the Spax then the originals being a single piece alloy unit. I hope these ones won't be off for a long time but when that day arises the job should be much easier.
Spax rear Nov 2018.jpg
Spax rear
It will be a while before I can road test them and adjust the best damping setting as I have now taken the car off the road for a while as there are quite a few other jobs on the list to do between now and spring.
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

davidr
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Re: Dampers/shock absorbers for XJS V12

Postby davidr » Fri Nov 02, 2018 1:12 pm

Well done Pop - I'm always liberal with the copper grease when reassembling the rear springs and dampers - especially the original type as that stops the rust issues with the collets that you had. Sometimes no amount of bashing, heat and swearing will get them out so a bit of copper grease now pays off many years later!

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Fri Nov 02, 2018 6:29 pm

I absolutely agree David, I had the rear cage last out in 2002 (16 years ago) and although the springs and dampers were not seperated then the holding bolts were and re-assembled with coppergrease. They all just slipped out without any fuss at all this time like they had been put together last week. Needless to say that the new collets had a slight smear of it on any touching parts.

I keep detailed records of everything I've done to this car since I bought it in 1997 and it amazes me when I read back through the many pages now written just how much has been done.
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Mon Feb 18, 2019 5:02 pm

I'm now fine tuning the damper settings. I originally set the front and rear Spax units to about half way between hard and soft and had left things to settle so I could get used to any difference.

I felt that although at motorway speeds the car felt very planted, around town and in the lanes it was was rather harsh especially at the front.

The front ones have also developed an annoying squeek so I've used silicone grease on the bottom and top rubber bushings. While in there I also reduced the damper hardness a couple of clicks so I will see if it makes things better or worse.

Al
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

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steve_m
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Re: Dampers/shock absorbers for XJS V12

Postby steve_m » Mon Feb 18, 2019 5:48 pm

Don't forget to tell your insurers that you have 'modified' your car!

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Sat May 11, 2019 10:14 am

After experimentation, I've settled on the following settings:

Front Dampers 4 clicks up from softest setting.
Rear Dampers 8 clicks up from softest setting.
Front tyre pressures P600 40 psi
Rear tyre pressures P600 42 psi

These suit my car and requirements, yours may well be different but it could be used as a starting point if using Spax dampers.

(As a footnote, I always fully comply with the requirements and conditions of whatever insurer I use).
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'

davidr
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Re: Dampers/shock absorbers for XJS V12

Postby davidr » Sat May 11, 2019 3:38 pm

Hi Pop - interesting feedback.
Tyre pressures look quite high. I don't go over 30psi as I find it makes the ride harder and I don't intend doing 150 on the autobahn!
XJS FORUM COORDINATOR
1996 XJS Celebration Conv. (shown on the JEC stand at NEC Nov 2015)
2001 XKR Convertible

Previously enjoyed!
1989 XJ-S V12 Coupe. 2006 XJ TDVi Sovereign. 1995 XJ6 3.2. 2013 XF 2.2d. 2009 X Type 2.0d Sovereign estate

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poprivet
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Re: Dampers/shock absorbers for XJS V12

Postby poprivet » Sat May 11, 2019 8:19 pm

The P600 tyres are rated up to 51psi. I personally prefer stiffer tyres and softer dampers and find the combination gives the best for fast twisty roads and motorway running.

Very compliant and not harsh at all. I often carry quite heavy loads in the boot and the car feels very planted considering my driving style. I learned to drive in the early '70s mainly by watching the Sweeney on TV!
1988 3.6 XJ-S coupe
'Remember that the value of your investment can plummet as well as fall'


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