Which rear end setup would you choose to retro fit

[e46v12 477]

Hey team so i have purchased an E12 1st gen 5 series, I'm looking at dropping my s85 into it. 

I would like to also bring the whole front and rear suspension up to modern standards.

So calling out all the suspension guru's out there, if you had the option to make any setup work with the car which one would be the best?

Example I was thinking of grafting the whole rear end and front from a e46 into the car. But after a bit of research the e9x series could be a better option, my engineer friend has said the e39 setups are pretty good too.

So looking at getting some advice or opinions on which setups would be the best fit for the car.

Thanks Richard

[Olaf 3317]

I'm not a suspension guru... looks like e46 is good for ~300hp, e60 M5 good for ~550hp.  I'd guess there's measurements involved... and (before you're cutting any steel) engaging with your certifier to run your design outline by them, determine what threy'll want to see as you progress.

Got pics, or a project page?  I'll subscribe, sounds like a really interesting build.  Yeeehah!

[Neil McCauley 394]

I did a end of year project on suspension kinematics at uni, but the more I learned the less I knew...

... this site has some awesome articles and is a good place to start, I wish I had this resource in 2004!

From a design perspective, the E90 stuff is pretty hard to beat. Multi-link is a massive step up from semi trailing arms, but the calculations required for things like spring rates are massively different - See link above.

Fortunately the E90 stuff (complete, including the front sub frame) has been used front and rear with an S85 in the past, although it all went into an E30 M3, so it "is" possible. See the pics attached for a possible solution - custom cradle for the rear using the same E90 pickup points, and then get that mated to the shell. Wide body will be the next step if you keep the sub frames the same width though.

If you're looking at the simplest solution at getting the power to the ground, I'd suggest a 4-link and tubbing the rear to the width of rubber you want to run - there's really nothing wrong with McPherson struts up front, and you can always build some custom coil overs with rates to your fancy. I've seen it in the rear end of an E30 with 650whp and it was an economical solution to the trailing arm problem.

 

 

[e46v12 477]

On 5/3/2024 at 7:33 PM, Olaf said:

I'm not a suspension guru... looks like e46 is good for ~300hp, e60 M5 good for ~550hp.  I'd guess there's measurements involved... and (before you're cutting any steel) engaging with your certifier to run your design outline by them, determine what threy'll want to see as you progress.

Got pics, or a project page?  I'll subscribe, sounds like a really interesting build.  Yeeehah!

Hi @Olaf yes i have had a talk with my engineer and he said it is very much doable. Just need to take some pictures of the e12 underbody and come up with a game plan with him. I haven't started a project page just yet, once I get it started i will indeed document it all. 

@Neil McCauley Thanks heaps this is pretty much what I was looking for, Chances are either e46 or e90 at this stage just depends what the certifier says and how much work to make either setup fit. But thanks for the site and pictures they help out heaps.