the differences between M029 and M030 suspension

HI everyone. I've just joined the forum. Can I ask what the M030 suspension would include for a 996 C2.1 please? Shorter and stiffer springs and different dampers is what I know so far, but are the bushes or ARBs different too? My situation is that I've just put a deposit down with an independent dealer on a really lovely and beautifully presented car that has had (I quote from the dealer's advert) a "full/comprehensive “M030” sport suspension overhaul". This is how it's advertised, and that is why I wanted to buy it. The test drive and a peer underneath established that it's not running M030 dampers, as advertised. I was told that they were an upgrade, but after a few phone calls yesterday it transpires that they're not designed for the M030 springs, and whilst they'll work (albeit underdamped), the car could even fail an MoT due to a length mismatch. I'd like to negotiate swapping them for M030, but is there anything else I need to check? ARBs? Bushes? Many thanks

would have been a useful question and answer for others to understand rather than just deleting it @RobManser

My apologies. If you'd like to re-instate the thread, please feel free. I think I was asking about the differences between M029 and M030 suspension? I actually answered my own question by remembering I had the Paul Frére book, which has this table in it: So in summary, 996 M030 brings changes to springs, dampers and ARBs, along with a reduced ride height.

Quotes source post: 2785068

let me do that, as the answer is very helpful which Paul Frére book do you have ?

Thanks. I was cautious at the time because I'd viewed a car that claimed to have (I quote) a "full/comprehensive M030" upgrade, done by the dealer selling it. It turns out they only did the springs, and after making some calls I'm looking at over £2k to get it to M30 spec (dampers, plus fitting of a 2nd hand ARB I've found on this forum). I didn't want to upset them, as they will probably read this, and I do love the car and want to buy it. I was just confused and surprised to discover this.

Quotes source post: 2785608

I have the "Porsche 911 Story" - it's a huge bible on everything 911. I bought it many years ago, as I've been keen on 911s my whole life. Mine is the 8th edition.

I think we can all guess who the dealer is based on this info..... pretty sure i looked at it online very recently.

If it helps you can download the Porsche 996 parts catalogue from the official Porsche website. Takes a bit of getting used to to interpret but very helpful when there are multiple spec options such as X029 (standard) suspension and M030 (sports) suspension and variations for manual and Tip transmission and then throwing in PASM... https://www.porsche.com/uk/accessoriesandservice/classic/originalpartscatalogue/

An update: I've now bought a 996 with a genuine M030 kit from new and I'm very happy with it. I think it's coming up for new bushes and dampers soon, purely through age (mileage is only 44k), but I like the setup.

Sounds great..what's the spec of the rest of the car?

Quotes source post: 2789036

It has the essentials that I wanted: cable throttle & M030 suspension with sports seats. It also has an updated hi-fi, which as a music lover I appreciate. Short shifter and sports exhaust too. It has an LSD, which I’m not sure is necessary, but I may change my mind on that as I get to know it. That’s pretty much it, and I plan to keep it standard and original, other than adding a steering wheel spacer, which is something I’ve always done to all my cars.

Quotes source post: 2789017

Whatever spec of suspension from new until now a refresh of the parts will be night and day different (and back to as Porsche intended) as everything will be a bit tired, a bit worn and a bit soggy after around 25 years.

Quotes source post: 2789899

Indeed, yes. It's got 44k on the clock and is 28 years old. I'm hoping to run the car for a year and then ask Autofarm to fresh the bushes and dampers. You can tell it's a nice setup, and all well matched, but clearly the dampers and bushes are getting a bit tired now - recovery from bumps on primary and secondary ride isn't as sharp as it should be. I suspect it might be a little too stiff for our bumpy roads when done, but it's the matching I'm keen on. That car I had a deposit on had standard ARBs, M030 springs and a Koni damper recommended for standard springs, and yes, the ride was cossetting, but it was clear it didn't all match. Do you know anything on the aftermarket arms available, or for such an original car is it best (and affordable?) to stick with official Porsche parts? For the dampers, Bilstein claim to sell the same damper as M030, just without a Porsche sticker on it.

Assuming the Koni was their Special Active, it is compatible with both X029 and M030 and M030 spec springs and they are more developed than the original Bilstein shocks to give better control. That said the current Bilstein option will likely be improved over the original, as damper tech has moved on (like oil, tyres etc) in the last 28 years. I put them on my 986 5½ years ago and along with everything else in the suspension being new it was pretty much a different car so much more planted and controlled in its responses. Not cheap but essentially a major return on investment in terms of driving reward if not car value once done. Porsche official parts are enormously expensive and will double or more the cost of the project. If you can find them in the aftermarket, TRW are the OE supplier to Porsche for arms and drop links (and the steering inner and outer joints too - changing these even if no detectable play is present makes a surprising difference just tightening the response up a touch and adding positivity to the feel and quite cost effective) and their parts have the Porsche numbers on them, just the Porsche Design logo ground off. Otherwise for coffin arms (highly unlikely you will find TRW ones of these) CTE and Meyle are good quality options. Spyder Performance look competitively priced but there are several reports of the coffin arm ball joints failing sooner than they should (one of mine did and they replaced it FOC but still a partial strip of one corner and a fresh geometry check so really far from a free replacement.) also their bush hole sizes are not all identical with the original Porsche design so if you wanted to put in poly bushes they'd be custom ones and the OE Match options from Design 911 haven't been around long enough to know whether they will last 40k miles and 10 years or only half that.

Yes, they were Koni Special Active, and I spoke to Koni UK and Centre Gravity about them. I asked an open question, and both independently confirmed that the Koni Special Active dampers have fixed bump and rebound rates (though they do adapt dynamically to bumps) and are designed and set up for the M029 springs. CG stated that whilst they'll work with M030, the spring will be left a touch loose on full droop (a possible MoT issue) and the damping will be too soft for the spring. I can confirm from my short drive that they didn't feel like they matched the spring. From a theoretical standpoint, this makes complete sense, and I can vouch for this as a physicist with 20+ years of setting up racing cars: springs and dampers need to match (note the frequencies given in the table I posted above; they're different between M029 and M030). When setting up new dampers on a racing car we'd always start full soft and then increase gradually, and you can feel the damper coming in to match the spring; you then tweak the handling after that. In terms of handling, note also from the table I posted that the M030 spring rates are not only higher than M029, but higher at the back relative to the front, which further complicates things when you have a fixed damper rate, because the mis-match will be different front and rear. There's a good overview of the basics of springs and dampers here: https://www.racecar-engineering.com/tech-explained/springs-and-dampers/ What I suspect is the case here is that whilst KSA + M030 is not ideal from a handling and tyre contact point of view, some people accept this compromise for a more cushioned ride, whilst enjoying the different weight transfer characteristics of M030 (and the look of the car, if that's your thing). Koni have confirmed that the setup works and sure, some people will like it. The dampers are not designed for the M030 springs though. This is all the theory, and obviously I'm fully aware that for my own car the suspension is tired (44k miles and 28 years old) , but you can tell it's a tired version of a matched setup, rather than a fresh version of an unmatched setup. To be honest, for my own tastes for road use in the UK, I think the 996 would be best placed somewhere between M029 and M030. I'm sure Lotus could arrive at a dreamy setup, and I've heard rumours that CG are working on something (I didn't ask them about this, it's just what I've heard). What matters above all else though is that the dampers match the springs. Thanks for your thoughts on the arms.