August 2022 - DIY Adjustable coilovers
There's not a great deal of options out there for coilovers, as 7/9 owners know all too well. In late 2021 I had tried sourcing some GAZ units through the excellent @AshDVS, however GAZ didn't have cores on hand, and my only option was to go to a pick-a-part and send them to the UK. Not ideal, and this had me pretty bummed to be honest.
What I've gone ahead with was pretty far down my list of desired alternatives - full-length strut bodies don't leave much stroke on a lowered 940, as we will see soon. But let's not get ahead of ourselves - let's build some cheap and hopefully-not-nasty coilovers.
The strut conversion parts sourced from BNE Dynamics/Kaplhenke Racing and other parts from DVS as mentioned lower in this post.
Disassembly
Take out your original struts, ceremoniously remove your chopped king springs without the need for spring compressors and then start hacking off the spring perch with an angle grinder.
Remove the strut from the housings.. I picked up the bilstein 1/2" tool from a mob in sydney to make removal and re-install way easier.
Now, grind down the remains of the spring perch, carefully so as to not remove any more material than is necessary.
Once the material is gone, I slid on the stop rings and left about 25mm of space above the top of the threaded collar, marking where I'd have to grind back the surface finish where I'd need to weld the stop rings, in order to get a decent weld.
Once marked and ground back, weld stop rings onto housings in the same place on both sides. The stop ring and the strut tube were both measure as being about 3.5mm thick so adjusted the MIG to what would suit that thickness.
Tacked it in 4 spots , then alternated welding the sides of the tube in 4 goes, to try avoiding any warpage of the strut tube. Again, I am an amateur at best but I believe this will be fine for the purpose. If you do this yourself, I take no responsibility for anything that happens as a result. :)
Spray the housings with some etch primer and suitable durable paint, then re-assemble.
Spring rates and details are:
Front: 250lb/in (~4.5kg/mm) Eibach Platinum barrel springs
Rear: 175lb/in (3kg/mm) Eibach XT 5.0" springs
Spoiler alert, the chopped king springs were stiffer than these rates, and this later becomes an issue.
Re-installed the struts with the RCAs from BNE with the quicksteer setting set to the middle hole (20% faster steering). Hugely appreciate the change - it's like it was meant to be this way from factory.
After taking it for a late night test drive up the street, I found that with using the faster steering holes meant the wheels were aligned with like 10 meters of toe-out. Pretty hilarious when I look back at when I was driving down the road wondering 'what the hell is that noise?'. That noise was tyres going in opposite directions.
It was completely impossible this would drive as-is, so I decided to do some internet research about how to do a basic string alignment at home.
I set it up with some fishing line and PVC pipe I had lying around with slots cut into it, and broke out the rulers. I managed to get it steering straight and it surprisingly felt quite good even with my rough alignment.
Replaced the rod ends at the same time since I had to adjust them anyway and had them on hand. Old ones were pretty cooked, as were the lower ball joints so replaced them too as part of all this.
Took it to a place that I'm really not happy with, so I won't post anything about the business lest I let my tongue slip. Ultimately, they kept ignoring my requested alignment settings, and kept claiming they knew how to adjust the BNE style strut tops, but were adamant that turning the strut top was only for caster adjustment, not caster and camber. Ended up standing there, getting them to make changes, and they saw on their alignment monitors what was happening relative to caster and camber.
I don't like to be that guy who hovers while a workshop does work, but when you bring it in with -3 deg of camber and they claim they can't achieve the -2 degrees you ask for after wasting literally hours of time, I lose a bit of patience.
Anyway, ended up with a streetable setup, but upon first decent drive and first few potholes, I found it crashing badly, feeling like it was slamming into a very hard bumpstop.
I figured out with some help from @AshDVS that the original king springs were actually around 6KG front and 4KG rear after they were chopped, using an online calculator and measuring up the original springs. Therefore, the selected ~4.5KG fronts and ~3.1KG rears were way softer. It made for a really nice ride, but was bottoming out on the shock and it was bad. I was not going to accept having to raise the car, so time to replace the springs again.
At the pain to the wallet, I decided to go with:
Front: Eibach XT 350LB (~6KG) springs w/ Hypercoil helper springs to keep it captive when jacked up
Rear: Hypercoil 250lb (~4KG) rears.
With a motion ratio of 1.22 on the rear (found somewhere on tbricks) that makes the rear around 5.4-ish KG/mm effective.
After disassembling and re-assembling, it feels firmer, though more like it did before obviously, but better than how the cut king springs felt. I lack the words to accurately describe the difference, but more controlled and less bouncy perhaps?
I want more options for shock adjustment but at least for now, this feels like a good balance between streetability and fun in the twisties. Still sad that I wasn't able to pick up a set of GAZ units for the front and have seemingly wasted a lot of time and money for just some height adjustment, and not far away from where I started. I will keep searching for options for upgrades for the future and if anyone has suggestions for a decent replacement for this, let me know :)
