C4S suspension upgrades- Bilstein B6 , M030 etc

My 4S is off the road, with an ever growing list of things needing sorted, but anyway, the cars 2002 and it's done 65k, the suspension never felt great since I bought the car and after having a closer look one of the spring platforms on the standard dampers has cracked. Today was spent looking into options and I seemed to land on Bilstein B6, standard springs, with a new pair of spring mounts, but I also see the M030 kit is listed by the usual suspects and includes springs and ARB's. I have searched, and searched to try and get a definate answer as to whilst the 4S is listed this would actually be an upgrade, or a downgrade even. Has anyone with a 4S actually fitted this kit? The B6's all seem very very expensive for the tech- and similar cars price points but hey, Porsche.. The cars already costing a fortune and I don't need ohlin's or 3 way KW's, the cars 100% a road/weekend car but I want some handling back.. Thanks

My C4S had relatively fresh bilstein B6s on the front when I bought it in 2017. The rears were original and so I replaced them with B6s in June this year. Any new damper will be an improvement. It isn't really possible for me to opine on how they comparre to anything other than the ones they replaced. They are a huge improvement on the original worn ones. The Factory damper is a variation of a B4 I think. While Bilstein only seem to offer B4 as a standard replacement, the Parts catalogue suggest that there were variants of the Bilsteins that Porsche fitted in the factory - e.g. the Porsche Dampers for Cabrio or Targa have different P/N to the standard C2 and I think this is due to the different weights of the cars. If the original springs are still good, why change them unless you want a different ride? If they have sagged, then yes they need to be changed. When I bought the rear dampers - I bought new top mounts TRW drop links and change them on the rear too. The C4S is 10mm lower than the C2. The ride is slightly firmer than the C2 I believe too. My philosophy is that Porsche put a lot of time into the suspension specification to meet most requirements. Obviously there is compromise. However, I haven't read a reviews of the 996 C4S when it was new, that said the factory suspension wasn't up to the job, and hence, fresh factory spec dampers at an affordable price is good for me. Also, I believe the factory spec car is capable of far more than I am. While I could fit more expensive dampers, their capability would be wasted on me!!! If I had lots of cash to spare, I think I would go for ohlins as they look nice!!! As an aside - I have a set of rebuilt Hartech suspension arms arriving tomorrow as rubber bushings don't last 16 years, and while mine are not knocking, I think they are well past their best before date and not as supple as they should be. not sure if this helps you, but hopefully it does.

Thanks, the B6 do seem superior, it was more around if the 4S basically already has the C4 M030 kit from the factory, so it would be like for like replacements, albeit newer ones. I already have a pair of top mounts to go on, one was creaking away but will do the pair

I've nearly finished my suspension refresh, shocks and a few final bits coming tomorrow. Mine is my DD so I didn't want anything firmer and don't need expensive coilovers. I've gone for B4's and the Eibach Pro kit giving a 30mm drop. I've also replaced all four coffin arms, tuning forks, drop links and ARB bushes. I'm hoping it's going to tighten everything up and give a better feel. I did think about swapping the ARB's as well but I can do those later if needed.

Short answer is No - it doesn't have the same shocks or springs as the C4 M030. the C4S had specific springs and was 10mm lower than standard and matching specific dampers based on the part numbers in the catalogue. I haven't been able to find any specific info on the differences - I did a lot of searching before I gave up and went with the B6s to match the fronts.

I am also not sure/convinced that the B4 would be the correct standard replacement damper for the C4S as it had firmer damping than the C2 when new based on the historical information available in online reviews etc. I think the B6 is your best starting point based on that alone.

I replaced the original with an MO30. Kit came with new arms and bushes. Worth it in my opinion. Car handles as it should. Like you I wasn't interested in ohlins and the like as it cruises about 10k a year on the M25, M23 and SW London! £1200 for the kit £890 labour

Thanks, did the ride height look the same?

I was looking at Koni sports as I thought my suspension would need doing soon but apparently its okay so no urgency. I will however be keeping an eye out for some deals over the winter. Not sure these are available for the 4s mind you, come to think of it when I had mine there was not a lot of options IIRC.

No Koni 4S/Turbo options that I could see when spending far too long hunting over the weekend

I have ordered a set of B6's from buycarparts.co.uk which actually seems to be a German company based on the correspondence, a useful saving over the UK suppliers, and I think I checked most of them New top-mounts all round as well so hopefully a noticeable improvement!

Have you fitted the new bits yet? I'm interested in this thread as my 4S has done 113k miles and as far as I know is on the original shocks. Various bits of the suspension have been refreshed as I've gone along, but the car has rather a harsh 'crashy' feel but to be fair drives fine, IMO. I know its a sports car, but I can't help but wonder if some new shocks might restore a bit of suppleness, or at least get it back to feeling at the manufacturer intended. Design911 have a Bilstein B4 kit for the 4S MO30 which comes up as OE... but is it properly OE... did Porsche just use standard B4s, or was there some secret sauce? Is the Bilstein B4 the best option for the money, or should I consider other options? I'm a road driver, no need (or funds for that matter!) for adjustable Ohlins etc.

Looking 2 replacement my c4s shocks. What did you go with in the end

Lots of chat about the dampers, make sure you check the state of all of the bushes too. There's not much point having new dampers if the arms are all shot. I went with KW v3s on mine as I wanted to lower it, its not a daily driver and it goes on track once or twice a year. I ended up not only replacing the dampers, bump stops and top mounts but all of the arms as well. And the drop links. If you're on the originals, you'll probably need to budget for replacements. I had mine done at RPM Technik. They replaced all of the rear arms along with the dampers/bumpstops/topmounts. Then I went to Center Gravity who re-did some of the setup work (it was too low, lower than any GT product, the bolts hadn't been torqued under load, the rear springs were too hard) and they identified that most of the front arms needed doing. Then when I had it serviced, they identified that the front coffin arms, the only remaining original parts, needed doing too. That journey was frustrating as I'd asked RPM to replace the lot and they said it didn't need it. Still, all done now.