David Jenkins
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| posted on 6/9/06 at 03:26 PM |
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Would single shear be so awful? I have seen examples that have worked well (trouble is - I have a good idea what the answer will be!).
Having looked at the drawings I can see that I could grind off the old shock brackets and use the same bolt for the top swinging arm and the lower
shock eye. This is a simple angry-grinder job, plus a couple of longer bolts. Trouble is, if I want to avoid single-shear then I must weld some extra
metal on, which really means getting the axle out.
This option means spending a fair bit of time but very little money. Changing the shocks and springs means far less effort but lots of money!
Any thoughts?
David
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MikeRJ
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| posted on 6/9/06 at 04:42 PM |
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Personaly I would want to put the bolt in double shear, it's supporting at least half of the weight of the car and over rough ground will have
very high transient loadings.
I nearly did this to try and use some 14" shocks on my GTS De-dion, but there was no simple way to weld in extra metal to support the bolt in
double shear, unlike a normal live axle. Had to shell out for some new shocks in the end.
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David Jenkins
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| posted on 6/9/06 at 04:59 PM |
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I think it's a quarter of the weight! 
I know what you mean though... at least with a live axle I should be able to arrange a second support.
David
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chriscook
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| posted on 6/9/06 at 05:05 PM |
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I wouldn't want a corner of my car supported on a bolt in single shear. A fairly standard loadcase for vertical loading is 3x the staic corner
weight of the car - if you want to do the maths. Don't forget the fatigue on both the bolt and bracket - a higher grade bolt won't
necessarily last any longer as its fatigue properties are probably worse.
You quite oftenn see dampers fitted to production cars fitted in single shear to the arms but this is just the damper remember and is not carrying the
spring load.
Chris
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MikeRJ
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| posted on 6/9/06 at 05:31 PM |
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quote:
Originally posted by David Jenkins
I think it's a quarter of the weight!
Dammit! I was thinking "half the weight of the rear" as I was typing that, but obvioulsy my decrepit brain was sending the wrong messages
to my fingers!
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David Jenkins
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| posted on 7/9/06 at 10:28 AM |
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Well, it was all academic anyway - I had a good look at the rear suspension this morning, and realised that I couldn't just use the top
swinging arm bolt - the top shock mount doesn't line up with the side of the bracket.
So, it's new shocks, when funds permit.
David
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David Jenkins
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| posted on 8/9/06 at 12:21 PM |
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I'm puzzled
I have been looking at the shock specs - if I get 12" open-length ones they come with 3.5" free movement, but the bump stop takes 1"
of that. Is 2.5" going to be long enough? (he said, looking down).
This shock length would give me the correct ride height, but I was wondering if I'd have enough travel when using 140 - 150 lb/in springs.
cheers,
David
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NS Dev
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| posted on 11/9/06 at 09:15 AM |
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Think you have all the advice on this thread, just in bits all over the place.
Basically you need somewhere between 12 and 13" shocks, with around 140lb/" springs, and half decent dampers. Forget moving brackets etc,
and remember your old shocks will sell on here or ebay.
Need not cost a fortune. Dampers which will work ok but not be anything special will be around £60 each and the springs are £12 each iirc from rally
design.
procomp will offer good advice if you give them a call.
ps. nice to have a thread talking sense on rear suspension........no silly spring rates and elastic band tyres mentioned!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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David Jenkins
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| posted on 11/9/06 at 09:26 AM |
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You're right - I have now decided to get the new shocks and springs once funds permit.
The only question that hasn't been answered is the one about available travel: 12" shocks have 3.5" travel, of which 1" is
taken by the rubber bump stop. Is 2.5" enough travel?
This is why I was also looking at moving brackets to use my existing 14" shocks, as they have a lot more free travel. Unfortunately that option
involves a lot of hacking and re-welding, including such nice tasks as draining and removing my petrol tank (I'm not welding 3" from
THAT!). So - new shocks it is...
cheers,
David
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MikeRJ
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| posted on 11/9/06 at 10:00 AM |
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quote:
Originally posted by David Jenkins
You're right - I have now decided to get the new shocks and springs once funds permit.
The only question that hasn't been answered is the one about available travel: 12" shocks have 3.5" travel, of which 1" is
taken by the rubber bump stop. Is 2.5" enough travel?
The bump stop does not remove 1" of travel, it just exponentialy increases the spring rate as it is compressed. Obvioulsy it will limit travel
to some extent as you can't compress it down to zero length.
The GTS uses 12" shocks on the rear and there doesn't seem to be an issue with them.
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David Jenkins
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| posted on 11/9/06 at 10:05 AM |
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Cheers to all!
David
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