Shock absorber alignment

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skiday
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#1 Shock absorber alignment

Post by skiday » Fri Nov 25, 2011 12:56 pm

And so to the next puzzler....

When fitting my front shock absorbers I saw that the anchor point on the lower suspension arm does not seem to be directly below the top anchor point. The spacer projects it forward. I have to force the bottom of the damper forward to mate with the anchor point. I have tried jacking up the suspension to it?s working height, but does not bring the anchor point rearward.

Image

I can?t understand why there is a space of about 3mm between the suspension arm where it meets the picture frame, but at the damper lower mounting point there is a spacer of about 20mm. I can see why the spacer is needed, because otherwise the damper would foul the arm, but it still doesn?t seem right. It is the same on the other side of the car.

Image

I have new frames from ETF, and the old frame looks to me as if it?s been ?eased? just that little bit to allow for this, but I find it hard to think that that should be the correct way to proceed.

Image

Thanks for your help

Andrew
Andrew Day. Former owner of S1A 4.2 2+2. Current cars; Aston Martin DBS 1968, Ferrari F355 & Fiat Coupe 20vt. Flag of choice; EU

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PeterCrespin
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#2

Post by PeterCrespin » Fri Nov 25, 2011 10:34 pm

The bolt for the lower mount passes through a top hat spacer, the 'brim' of which aligns the damper. It would foul or risk fouling the top wishbone otherwise.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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skiday
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#3

Post by skiday » Fri Nov 25, 2011 11:35 pm

To me it seems, as can be seen in the photo, it is because of the top hat spacer that the lower damper mount is out of alignment. As you can see, it is fitted, were it not, the mount point would fall exactly within the two yellow lines drawn.
Andrew Day. Former owner of S1A 4.2 2+2. Current cars; Aston Martin DBS 1968, Ferrari F355 & Fiat Coupe 20vt. Flag of choice; EU

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christopher storey
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#4

Post by christopher storey » Sat Nov 26, 2011 9:01 am

The way you have it looks entirely correct to me. The damper does indeed "face forward" . The geometry is quite complex on these cars with adjustable castor resulting from screwing the upper wishbone pivot backwards or forwards as required, and the damper also is canted forwards as a result

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vipergts
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#5

Post by vipergts » Sat Nov 26, 2011 9:50 am

christopher storey wrote:The way you have it looks entirely correct to me. The damper does indeed "face forward" . The geometry is quite complex on these cars with adjustable castor resulting from screwing the upper wishbone pivot backwards or forwards as required, and the damper also is canted forwards as a result
I maybe reading that wrong but adjusting the caster won't move the shock.

The top wish bone might interfere with the shock but thats about it....isn't it?
S1 4.2 Roadster in Resale Red

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christopher storey
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#6

Post by christopher storey » Sat Nov 26, 2011 1:03 pm

Well,I think altering the castor affects the tilt in a fore and aft sense of the whole suspension unit because screwing the rod back and forth takes the top wishbone with it . What there is no doubt about in my mind is that Andrew's pics show his bush/spacer in exactly the same positon as those on both my cars . For whatever reason, the bottom of the damper is designed to be held forward of a flush position with the lower wishbone, exactly as shown in his pics

Edit : I've just been looking at mine, and I see that altering the castor moves the top wishbone and the suspension upright , but not the lower wishbone, so you are correct about the damper staying in the same plane

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PeterCrespin
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#7

Post by PeterCrespin » Sat Nov 26, 2011 6:17 pm

skiday wrote:To me it seems, as can be seen in the photo, it is because of the top hat spacer that the lower damper mount is out of alignment. As you can see, it is fitted, were it not, the mount point would fall exactly within the two yellow lines drawn.
Looking at your photos two things stand out:

1)If your spacer is really 20mm it is too thick. It doesn't look that big but if it is then it's bigger than mine. Mine is closer to half that but I haven't got a measurement handy. If it's an original long sleeve with the wider brim section then maybe you're guess is high and my guess is low and in reality they are about 15 mm?

2) Your lower wishbone loks too far forward. The leading edge of the wishbone blade should be about 4 mm(?) behind the trailing edge of the picture frame, judging by my two cars. They are handed in the fore/aft plane so maybe you got them mixed up or they are bent? I think it would only show up when assembling the torsion bars, but maybe I'm isremembering. Anyhow, from your photo it looks noticeably further forward than mine. Are you using standard rubber wishbone bushes and spacers/washers?

One thing's clear (IMHO) - correctly assembled dampers and suspension should not result in significant displacement for or aft of the damper, give or take a tiny bit from missing or mis-placed washers either side of a top or bottom damper bush or wishbone bush. The dampers should be pretty much vertical and if they are that far out there's something up. Unfortunately I only have my 1 metre builder's spirit level available and it doesn't fit along the damper without hitting the bonnet so I can only judge by eye. Mine look fine.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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vipergts
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#8

Post by vipergts » Sat Nov 26, 2011 8:13 pm

I could be wrong and will have to check but the shox I fitted to my car negated the need for a spacer because the botton end of the shock was wider that the original.

This could be the case with yours??
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mgcjag
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#9

Post by mgcjag » Sat Nov 26, 2011 9:11 pm

Hi All.....When putting the front suspension back together on my S2 2+2 I noticed exactly the same thing...With only the top of the shock connected there is a considerable amount of movement available on the bottom, the spacer on the bottom shock bush sleeve accounts for the difference in width of the top sleave of the shock compared to the bottom, and after connecting up the shock the centre line of the shock & frame was as near as possioble to parallel. I set the ride height & geometry with no noticable problems. Do remember that the weight of hub when connected to the top & bottom wishbones should not be allowed to hang without the shock connected or supported as the top ball joint can be damaged (according to the manual..Steve
Steve
69 S2 2+2 (sold) ..Realm C type replica, 1960 xk150fhc

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#10

Post by PeterCrespin » Sun Nov 27, 2011 1:25 pm

mgcjag wrote:Hi All.....When putting the front suspension back together on my S2 2+2 I noticed exactly the same thing...With only the top of the shock connected there is a considerable amount of movement available on the bottom, the spacer on the bottom shock bush sleeve accounts for the difference in width of the top sleave of the shock compared to the bottom, and after connecting up the shock the centre line of the shock & frame was as near as possioble to parallel.
Found my shorter spirit level and the dampers are dead vertical. Granted, that's taking a reading off the outer dust shroud on the Konis, which isn't exactly a daaum surface, but it's good enough.

I wouldn't stress about a degree or two from vertical but anything major would need sorting out, if only to prevent a tendency for the damper to 'walk' off the bushes, s one sees occasionally with the anti-roll bar bushes if the large security washers are omitted.

Pete
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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abowie
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#11

Post by abowie » Sun Dec 25, 2011 1:45 am

Something's bent, the wrong size or misassembled. For one thing you have a lot less clearance between the upper wishbone and the shock than I do. It looks to me like the whole upper shock mount is sitting too far back. I know that would mean that the engine frames were suspect and that that's pretty unlikely but...the fact that your old mount has signs of being "eased" makes me wonder.

If I could work out how to put in an image I could show you mine..

http://www.flickr.com/photos/71499700@N08/6566793799/
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1979 MGB (supercharged).
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johnben
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#12 Shock absorber alignment

Post by johnben » Sun Dec 25, 2011 9:08 am

If it's any consolation my shocks are at an angle too. I remember when I replaced them that I thought I would sort it out, but in the end I gave up as without major work it is difficult to see how you can get them back in line. The good news is they worked before and they work now, albeit I am still uneasy about them not looking right.

John Ben

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