At the moment I am about to start the build of a locost 7 (lotus 7 replica) and on the aussie builder's website of late the De-Dion rear axle has been a hot topic. basically from my limited understanding the dd combines the best attributes of a solid axle with the flexibility of an IRS and is able to package the two in a small area for a relatively small outlay. (and is easy to build for people who don't have degrees in automotive engineering and want to build something that has been tried and tested and will work straight out of the box ehe) anyway here is a pic of it. I'm sure with minimal fabrication one of these could be built into a 1200 and you could choose any diff you wanted (say R180 or even 200 if you're really gonna abuse it) and you can get LSDs fairly cheap (like OBX's) or KAAZ (on the more expensive side) and readily available. anyway here is a pic so you can get a basic grip of what I'm trying to say..

sweet never seen that done or would of considered it, the been some talk on here about those de dion rear end setups. how does the weight of the brace compare to axle tubes?

De-dion is a cheap alternative to IRS. For roadholding and sheer cornering, it has no advantage over a carefully setup live axle. But potentially will have better handling. The 610 IRS swap is a documented swap for 1200s and looks a bit easier to do. But that's only if you want a softer, smoother ride, or for good handling on bad roads.

My 2c..

Bolt in rear coil overs for a 1200 do not exist.

The mounting points for the rear shocks are not designed to take the loads that coilovers will place on them, especially if you use them for height control.
All 3 1200 rally cars I have had has had some sort of seperation/damage to the top rear shock mounting points even when used as normal shock mounts (admittedly a much harder life than a street car), start putting sprung suspension loads through them and it is a recipe for disaster without substantial strengthening..

Wow this topic turned from easy, common upgrades for the back of 1200 coupes to exotic suspension redesigns that hardly anyone has done.

Replace bushes and shocks is all you need to do. Maybe resetting leafs to get camber back into them (if thats a problem), maybe replace u bolts if these are worn and causing movement.

To all the " know it alls"!!!!

Try reading this!
http://datsun1200.com/modules/mediawiki/index.php?title=Coilovers

Ive been planning on a DeDion rear end for my thouee for quite some time now and the best so far is using the Volvo 300 series rear setup which can easily be upgraded to disc brakes as per shooms photo from the Locost site. The volvo tube is quite strong and might be overkill for a datto but at least its cheap and has the important single leaf springs.




It allows the ease of using easier to source LSDs from factory models eg. Subaru, mazda, Nissan, Toyota, Mitsu, BMW and others.

Im on the search for an alloy lsd centre from a Benz but might end up using a commonwhore alloy irs diff.

orange-1200,
Just because it's in wiki doesn't make it a good idea or offer improvements to handling.
My car, before I bought it, was originally setup with 120y leafs (one leaf per pack - rear spring hangers moved further back to fit) and coil overs on the rear and, this was done with the intent to use for circuit racing, they removed it because it had an adverse effect on the handling quality. I was left with cleaning up this mess when I bought it and have gone back to standard and it handles much better now.

There are some good books out there that would help with understanding of the inherent limitations with leaf spring setups and how to tune them to make it work. Milliken and Milliken "Race car vehicle dynamics" springs to mind (This is my reference book when I get stuck).

I'm not saying you can't make it work, but it would be difficult and iterative (changing spring rates on both leaf and coil and also shock valving, Which means expensive). In my view it would provide one, maybe two, foreseeable benefit over standard leaf spring. That being the ability to adjust the ride height up only (really once set you never change anyway - I never have for street on my coilover fronts). May provide benefit to reduce axle tramp?

The negatives would be: difficult to match leaf spring to coil spring rates to get a balance (two springs in parallel changes the oscillation frequency compared to one, therefore you would need to re-valve the shocks to suit), would require very soft coil springs and therefore actual upward adjustment would be limited, extra stress on shock mount points (Now carrying load - as indicated earlier). softer leaf spring reduces leaf resistance in roll, may need to then add ARB.

Does not address inherent deficiencies with leaf spring being Ride and roll are still coupled, Roll steer still present, Potential roll centre height issues still present.
Therefore you get to change rear ride height, added weight, made the rear more complex and done nothing to address the leaf spring geometry issues.
This is my reason for not seeing the few pro's outweigh the cons.

After owning quite over 60 cars in my fourty plus years I found that many IRS setups although good they can cost quite some time and money to get right. However the De Dion Alfa Romeo gtv6 and Volvo 360glt are surprisingly amazing handling vehicles from factory with little but just good shock absorbers. Leaf springs are simple and effective to setup and datsuns of the 1000 and 1200 variety are so small and compact that IRS is not really needed however LSDs are not easily afforded unless you already have a h165 rear shortened, factory fitting or fits without shortening.

Wow sounds all very intense