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Suspension woes of an 11 year old Libra 
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Post Suspension woes of an 11 year old Libra
Recently decided to have a good look at the suspension on my Libra, given that it's eleven years old and still on it's original Avos.
1.8VVC no anti roll, used as an everyday car, no track use.

A good few years ago the (red)front springs broke and I got some 2nd hand ones (purple!) from Dudley at the old GTM place. The rear springs are the original red one's I got with the kit.

Current situation is this:
Front shocks in a bit of a rusty state but possibly retrievable with an Avo rebuild job (and a bit of wire brushing/repaint by me).
Front springs have lost their coating and are corroded but intact.
Only looked at the driver's side thus far due to space/time restrictions.

Rear shocks are corroded towards the bottom on the extension arms but are otherwise in pretty good nick, one side has leaked a little oil. I used a set of rubber m/c fork gators to cover from the adjuster knob down to an inch or so bellow the spring bottom. This is probably why they've survived so well.
These have been sent off to Avo for a rebulid and will be tidied up cosmetically when I get em back.
Rear springs, the drivers side has corroded and broken in two places near the bottom, how long its been like that i'm not sure due to the gators covering it up - a while though :oops: Passenger side spring is perfectly fine.

Front springs are 9.5" and rear 10.5" (1.9" ID) no rates marked on the ends. I did a bit of Heath Robinson testing using my drill press and some bathroom scales(!) to measure force and deflection - an idea I got from the net.
Now according to this very primitive test the front(DS) spring is 150lb/in and the rear(PS) spring is 165lb/in. Assuming these figures are correct this gives a number of possibilities, none of which are good.

A fresh start was what I need, so a new set of springs has been ordered from Avo. After trawling this forum and doing some hard sums :lol: I decided to put all the possible combinations into a hat and draw one out, and the winner was:
Front 8" 250lb/in Rear 10" 300lb/in

Given the laughably imprecise nature of the aforementioned selection process this could all end badly but at least i'll have a full set of proper working shocks and springs that I actually know what they are.

Question: Can anyone tell me what size the front susp arm poly bushes are? I fancy they could do with replacing too.

Will report back once its all back together and driven.

SAS


Mon Mar 21, 2011 6:57 pm
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Post Re: Suspension woes of an 11 year old Libra
i found out that poly flex do an adjustable poly bush for camber adjustment am waiting for an e mail if they would make them as a one off a good idea when wanting better grip on front end.


Mon Mar 21, 2011 8:42 pm
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Post Re: Suspension woes of an 11 year old Libra
Cor blimey, finding front wishbone bushes is proving a serious obstacle. I might have to end up machining my own

SAS

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Fri Mar 25, 2011 3:24 pm
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Post Re: Suspension woes of an 11 year old Libra
So after £24 worth of PU rod and a £7 13.5mm drill bit, i'm now halfway through making my own bushes. The PU is shore A90 and feels a little bit stiffer than the old blue ones, i'm keeping the original inner sleeves as they are fine (stainless steel too).
Machining this stuff is hard as the material is relatively soft and tends to deflect away from the tool - getting reasonable dimensional accuracy and a decent smooth surface is tough but I think they should be ok.

Of all the bush suppliers I emailed only Powerflex have got back to me showing any interest in supplying. Given that i'm currently doing the above I might not need what they offer but it might be useful for other Libra owners if they come up with something.

SAS

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Tue Mar 29, 2011 5:36 pm
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Post Re: Suspension woes of an 11 year old Libra
Super Flex supplied the bushes originally.

Bob S.

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Tue Mar 29, 2011 7:02 pm
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Post Re: Suspension woes of an 11 year old Libra
I didn't know that, were they custom or off some other car?

SAS

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Tue Mar 29, 2011 8:56 pm
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Post Re: Suspension woes of an 11 year old Libra
Custom, supplied with the kit.

Bob S.

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Tue Mar 29, 2011 10:52 pm
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Post Re: Suspension woes of an 11 year old Libra
Got this from Powerflex:
"I’ve managed to work out a combination of a bush and sleeve that modified slightly will suit your application

Bore 16mm
Barrel OD 22.5mm
Flange OD 28mm
Barrel Length Reduce to 11.5mm
Flange length 3.4mm
Total length 14.9mm
Inner Sleeve 16x32x11mm

These would be priced at £18.92 + vat each. This would consist of 2 PU parts and 1 stainless steel sleeve
Let me know what you think
Kind Regards
James Bourn ~ Sales Manager"


This would make a complete set about £182

The dimensions are similar to the originals except the old bore is 13.5mm, meaning there would be less bush wall thickness between inner sleeve and the wishbone tube.

SAS

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Wed Mar 30, 2011 10:27 am
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Post Re: Suspension woes of an 11 year old Libra
Also got a response from Crest:

"Hi Simon,
Unfortunately it does not appear we are able to source any bushes with precisely those dimensions, details of the nearest we are able to supply are listed below:

Flange Outer Diameter: 28mm
Flange Thickness: 2mm
Bore Inner Diameter: 12.5mm
Barrel Outer Diameter: 22.5mm
Barrel Length: 24mm

Flange Outer Diameter: 27mm
Flange Thickness: 8mm
Bore Inner Diameter: 13.5mm
Barrel Outer Diameter: 20.5mm
Barrel Length: 26mm

Further information relating to these bushes including a diagram are available to view on page three of the document http://www.polybush.co.uk/assets/mailsh ... 2010_1.pdf
If you have any further questions or wish to place an order please do not hesitate to contact me.
Regards,
Alex Forster
Managing Director
Crest Motorsport Limited"


SAS

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Thu Mar 31, 2011 10:14 am
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Post Re: Suspension woes of an 11 year old Libra
Got the front shocks back from Avo today after their rebuild, however the new spring seats wouldn't screw on (had to cut the old ones off). Avo said this would be due to the tatty condition of the threads on the body.
After some careful measurement it turns out that the new seats had a slightly smaller ID than the old ones "due to age of units and different tolerances for current production" Avo said. So I put the seats on my lathe and skimmed about 0.1mm off the thread tops and they then went on ok.
All I need to do now is tidy up and repaint the front PS wishbones (perhaps a new balljoint or two), fit my newly made bushes for that side, reinstall the front shocks and set the ride height and damper settings all round.

Oh and I just bought some of the Mk2 rear arms to see if I can make em fit with my 16" racelines. For that i'm going to make a mock up of one side of the back end and see where the problem lies and how severe it is.

SAS

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Thu Apr 07, 2011 5:00 pm
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Post Re: Suspension woes of an 11 year old Libra
Fitted all the parts yesterday and set the ride height, 5 3/4" rear, 5 1/2" front with no one in it and about 3/4 tank of fuel. Set the dampers to 8 clicks from maximum.
Took it for a short drive and all seems ok - firmer than before but no major concerns.

SAS

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Mon Apr 11, 2011 11:50 am
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Post Re: Suspension woes of an 11 year old Libra
Had a look at the mk2 rear suspension arms this weekend, created a mockup of the DS rear bulkhead out of wood and a piece of steel treadplate for stiffness.
Mounted the new parts and rear hub off the car and set the camber and toe in to as close to my settings as I could (note I run my rear with the bottom inside ball joint 2mm longer than the others giving a very small amount of toe and camber). The brackets were mounted at the same height as they would be on my car at rest with a 5 3/4" clearance at the rear of the sill.

With the wheel on and sat on the floor, the rim is about 1mm or so away from the inside of the top wishbone - clear but not ideal. I then calculated the max upward travel of the top arm to about 50mm as at that point the damper hits the bump stop. I jacked up the wheel on the test rig to 50mm above the ground and due to the geometry the camber increased making the rim touch the top WB.

All this is due to the new top WB having a straight member running from the steering arm mount point to the hub top ball joint hole. The old one has a dog leg in this member.

Three solutions are available as I see it, narrower wheels, wheel spacer plates or mod the top WB.
New wheels would be expensive and I don't like the idea of spacing the current ones out so I'm going to mod the top WB.

I'm going to cut off the offending member (ooerr) and replace it with a new dog legged tube, this will mimic the profile of the old top arm, steel plate will then be welded top and bottom of the top arm. One of the inner lattice tubes will therefore need shortening and another will be removed and re-angled to maintain that triangle.

SAS

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Wed Apr 13, 2011 9:59 am
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Post Re: Suspension woes of an 11 year old Libra
Does anyone know exactly what the 8 bush/ball joints are on the mk2 suspension arms?

SAS

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Sat Apr 16, 2011 11:53 am
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Post Re: Suspension woes of an 11 year old Libra
The saga continuums:
I emailed RDM for help with the mk2 rear arm BJs and got this:
Hi Simon
Thanks for the email. We sold GTM cars 4 years ago and do not have anything to do with the company anymore however the parts you need are from a Rover 75 and/or Rover 45 I can’t remember and also Ford.
I have the Ford numbers but don’t have the Rover numbers. Because the bushes are a press fit they used to be supplied with the upper and lower trailing arms so I don’t have the individual numbers for them but you should get these of the information from a Rover spares place.
T0307A REAR SUSP. ARM BEARING FIX’S - CAM BOLTS 4 FORD 6736548
T0307D CAM BOLT WASHER 4 FORD 6581717
T0307E CAM BOLT NUT 4 FORD 7062398
Good Luck and hope that helps
David

As you can see no numbers for the balljoints (bah) but the bolt # might be handy for someone.

Having searched based on this info I find that the 45 is a bust completely and the 75 has a similar balljoint on the rear susp. After much googling and a visit to a scrapyard the standard 75 BJ is correct in length and ID but the OD is too big at 45mm (ones fitted to arms are 40mm OD).
Its part #3.
Image

I then discover that the 75 V8 has a lot of different (rear susp) parts due to it being rear wheel drive and shares some of its parts with the MG ZT 260. Here's a diagram of the V8 rear hub and you can see part #3 looks a likely candidate:
Image

However i've yet to find any dimensions on this part or anyone who has it in stock to find the dims out from - probably due to the rarity of this model.

Plan um... C? Find a similar BJ to substitute. Long story short, more googling and a visit to GSF produces a Mercedes BJ which has a 40mm OD, 48mm long and 14mm ID.

Part details: Mercedes Model: 190 1982-2000 / C CLASS 1993-2000 / SL 1989-2001 / SLK 1996-2004 / 170 1946-1958 part OEM ref.:2013520027

I chose that one because changing the OD of the ring on the arms that the BJ sits in would be the most complicated to do. (all the others had a larger OD (vectra, saab, fiat, bmw)).
To use this Merc one requires a spacer tube to sleeve down from 14mm ID to 12mm ID and a 4.5mm spacer between the BJ and each side of the bracket - relatively easy to do. This would mean (with the necessary spacers) the Merc BJ could replace any of the original BJs that may fail in the future with no permanent mods to the brackets/arms etc.

Note, the BJs already on the arms seem ok but I didn't want to go fitting stuff with parts that I couldn't replace if they wore out/failed.

I still want to know if those V8 BJs are the ones.

SAS

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Wed Apr 20, 2011 5:00 pm
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Post Re: Suspension woes of an 11 year old Libra
Here's some pics:
Rear end mock up jig:
Image

Wheel rim binding on upper arm tube, this pic has wheel at rest position, gets worse as suspension rises:
Image

Modified mk2 arm showing new dog leg piece and repositioned bracer (grey metal is new):
Image

The cursed mystery bush (75 V8?):
Image

The mercedes bush:
Image

SAS

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2000 GTM Libra 1.8VVC 145BHP


Thu Apr 21, 2011 11:42 am
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