Konis or Gaz?

[ALAN COCHRANE]

Hi Everyone

One of my winter projects is to change the rear dampers and springs. I've had a look at what SNG offer and it seems to be a straight choice between Koni or Gaz. I only intend to use the car on public roads so ultimate performance is not the aim. Maintaining the standard setup and ride is more important.
There's a big difference in price so which one to go for? I see you also get Gaz black dampers for roughly the same price as the standard ones-is there a big difference.
SNG also offer what looks like a standard spring and what looks like an uprated Gaz(C25939) with fewer coils- I'm assuming this provides a firmer ride?
All advice gratefully received as always .

Cheers

Alan

[mgcjag]

Hi Alan....not sure if the S1 is the same as S2....but I used the boge shocks from SNG....I got them as a unit with the springs already fitted.....makes for a much easier job.. Steve

[abowie]

I agree with Steve; the Boge shocks are fine.

I would reuse your own springs and not replace them with new as new springs may well not be correct for your car, resulting in incorrect ride height.

Otherwise use the Gaz shocks. The Koni's are very expensive and personally I haven't seen the benefits.

[Dawnpatrol]

I'm going through a similar exercise at the moment but for competition spec dampers.
Check the dimension from the top of the spring platform flange on the damper body to the centre of the bottom eye, my Konis are 1/4" more than an original set of works spec Girlings, both fixed platform. This would raise the ride height by the same amount all else being equal.

Michael

[PeterCrespin]

my Konis are 1/4" more than an original set of works spec Girlings, both fixed platform. This would raise the ride height by the same amount all else being equal.

Michael

Nope. Significantly more than that. Look at the IRS: the damper attaches part way along a significantly longer lever.

[Dawnpatrol]

Yes good point, you're right, forgot about the geometry affect.
If I was really keen I would reach for my protractor etc.
If anybody is running adjustable platform rears if would be interesting to see the affect on the ride height of winding the platform up by 1/4" with the same springs.
Also, given the discussions elsewhere on the forum about ride height, this dimension from all the other damper options would be interesting.
The Girlings I have measure 2 1/8", however, they are not standard rates but dimensionally I think they are the same.
The GAZ fixed platform option is the same as the Girlings however, the GAZ does not use the collets and has a top hat shaped platform with an o/d of 3 1/2". So the spring has to go on from the top, and sits directly on the flange without the bottom spacer/spring locator, GAZ have affectively designed it in.
In the factory arrangement, the collets look like they reduce the affective length of the spring by an amount, not sure how much as my setup is not standard.

So, my advice to Alan would be to stick with a damper that has the this dimension the same as the original if you are sticking with your original springs and attachment arrangement, otherwise you might be better changeing the whole package, or go adjustable platform.
To clarify, I have not got the GAZ in my hand, they gave me a drawing so I could check, before I placed an order.

[ALAN COCHRANE]

Thanks for the replies. I seem to have overlooked the Boge ready assembled units when I first checked out SNG.
Since I want to maintain the standard ride and height they seem to be the way to go for me.
The car seems to sit lower on the passenger side when viewed from the back. This may be an optical illusion caused by the quarter bumpers so it'll be interesting to see if this is still the case with the new units fitted.

Cheers

Alan

[mgcjag]

Extra weight of fuel in tank......?

[PeterCrespin]

Depending whether it's an import, and the passenger side used to be driver side, it's very common for the LHS to sag on reimports.

[ALAN COCHRANE]

No it's not an import. It's spent it's whole life in various parts of the UK. The huge history file that came with it documents it's entire career right back to 1962. Even to the point of being able to verify that the odometer reading of 46.000 is genuine.
The original registration document came with it as well. It even notes it's colour change to signal red in1967. No need for an HPI check- it lists all the previous owners.

Alan

[abowie]

Since I want to maintain the standard ride and height they seem to be the way to go for me.
Cheers

Alan

Search the archives. Don't buy the new springs.

[abowie]

The car seems to sit lower on the passenger side when viewed from the back.

I have an original Aussie delivered RHD which has persistently sat low on the left. Objective measurement has confirmed this.

Last weekend I swapped out the LHS torsion bar for a different (used) one.

Car now sits perfectly level.

Make some measurements from under the lower wishbone as shown in the manual. Also measure the height from top of the wheel arch to ground at the front. Finally, put a spirit level across the roof. Support it on either side with identical props placed the same distance in from the gutter chromes.

If you don't have another torsion bar consider an adjustable torsion plate.

WRT the rear springs, once you have removed the shocks, measure all 4 springs for height. What I then did was took the 2 taller ones and put them at the back, then the 2 shorter ones at the front of the IRS.

[PeterCrespin]

Last weekend I swapped out the LHS torsion bar for a different (used) one.

Car now sits perfectly level.

Finally, put a spirit level across the roof. Support it on either side with identical props placed the same distance in from the gutter chromes.

What I then did was took the 2 taller ones and put them at the back, then the 2 shorter ones at the front of the IRS.

It's the same amount of work to re-set the known torsion bar, surely, by adjusting the link distance or turning the bar a known number of vernier fractions?

Spirit level on the picture frame is especially easy on part-built cars but with two identical blocks of anything is also easy on a fuly-assembled car assuming you're not using some cheap 8" level. Remember too that you should always check a level set both ways round, to cancel out any error.

What was the logic behind the front/rear spring locations? I thought you were going to say you paired the 'long' ones on the low side.

[abowie]

It's the same amount of work to re-set the known torsion bar, surely, by adjusting the link distance or turning the bar a known number of vernier fractions?

We discussed this, and you're quite right but I figured that the old TB was soft and if the replacement fixed the problem it would be a better outcome. My next move was the spare adjustable reaction tie plate I have tucked away.

[Jeremy]

Question for Alan: What did you end up doing about your rear springs, and with what result?

I'm a long way off refitting springs - I'm at the rust/grease/mud stage of my rebuild - but having just removed the rear spring/shocks I got interested in this and similar threads. I find no evidence in all the service bills of them ever being replaced and they don't look too pretty:

FWIW these shocks are stamped Girling Decarbon 7009 4299A KP12.

I wasn't sure about re-using 50-year old rusty springs...won't metal fatigue be setting in? Or the corrosion reduce the spring modulus? Yet after reading the expert advice I wonder if I should just get them blasted and repainted, and go for Boge standard shocks. There seems to be a huge variance in the specs of the various new springs available.

The car's ride height before dismantling looked perfect by the way:


This is most certainly not urgent! But any advice will of course be much appreciated.

[Geoff Green]

spirit level on any front door opening sill in any Jaguar should be level except for the special editions with different tire size front to rear I.E. XJR-S. It's a quick easy place to check.

[PeterCrespin]

Re-use the springs if the car sits right - EVERY time. De Carbon are gas shocks and the French firm licensed the tech to Girling in the mid 70s (ish) IIRC. They are good parts. They shouldn't mind lying on their side as thry are monotubes.

Once the springs are off the damper rod should extend by itself if you press it down, which is like a modern bonnet strut and shows they are still pressurised. Four dampers that take some effort to compress could have a minor effect on ride height and your car does look a tiny bit rear-high. But this is fine, especially at high speed when it will be less front-light.

All in all, if the chrome rods aren't rusted and the seals not damp, I think you have a great setup, so I wouldn't mess with it. Maybe refresh the end bushes if the eye looks off centre or the rubber is badly perished or soggy. They are probably fine. Countless owners have regretted throwing out original parts and this is one of the areas where blowing money can easily spoil what you had before.

[Jeremy]

Really helpful advice Peter, which I shall follow. Rebuild is already going to cost quite enough without wasting money on new bits that make things worse! And I hate throwing out things if a little care and attention will make them good again.

Front shocks have no identifiying marks, they are a sort of poster-paint blue. Do I assume Girling again, and same advice?

I saw elsewhere on the forum a recomm. for Vintage and Classic Shock Absorbers in Croydon. They will recon a Girling shock for ?60 +VAT, so I was thinking of them if I find damp seals or rusty rods.

Geoff, I will also do the spirit level thing when setting up the torsion bars. I did mark them but it will be a useful check.

Many thanks for the wise advice!

[ALAN COCHRANE]

Jeremy

Unfortunately the new springs did not alter the uneven stance issue. It did however improve the ride and stop an annoying intermittant squeek that was coming from the passenger side front.
I've come to the conclusion that the rear tub might be slightly off the square and since we're only talking about 5-6mm I'm leaving it for the moment.
I intend to investigate the torsion bars next winter in case they are the source of the problem. Although wouldn't they also result in an uneven ride height at the front as well? As far as I can tell my car appears to sit level at the front.

Alan

[PeterCrespin]

Front shocks have no identifiying marks, they are a sort of poster-paint blue. Do I assume Girling again, and same advice?

I saw elsewhere on the forum a recomm. for Vintage and Classic Shock Absorbers in Croydon. They will recon a Girling shock for ?60 +VAT, so I was thinking of them if I find damp seals or rusty rods.

Front shocks are likely solid Girling blue. Probably a faint outline G somewhere. E-types rarely do enough miles to actually wear out shocks, as opposed to corrosion failure but they are welded construction, not rebuildable by simple dismantling. If you feel strong, smooth resistance pulling vertically from full compression to full extension they are likely fine - certainly good enough to re-use and see if you like the ride/damping. If the fronts stay compressed on release they are twin-tube and these can get air bubbles in the fluid if left horizontal or upside down. Solution is to pump them full stroke a few times the right way up and the air/oil will return to their correct orientation.

So same advice, yes. You can always use the rebuild service later if they only last a few years (which I doubt). I can see the photo on a bigger screen now and the eye bushes do look fine. There are some horrible-riding E-types around (mine's no feather bed) but Jag knew what they were doing.

Pete