Your experiences of aftermarket suspension on the Z4 MC

I'd like to hear reports from anyone who has fitted any aftermarket adjustable suspension to the Z4MC.

I'm particularly considering Nitron R1 and KWV3 or KW Clubsport. I already have KWV3 on my Z3MC, which is a coilover set-up on the front with linear springs, but in the case of the KWV3 for the Z4MC, the set up only has progressive springs all round and so, I'm not so sure about it. I'm therefore interested in hearing from those who've got any of these kits.

I've previously run kW v3s and thought they were ok/fair. Changed to intrax which are in a completely different league compared to the KWs. They are a coilover all round and adjustable via a knob at the bottom of the strat- takes literally seconds to adjust per side albeit having 45 clicks in front and 30 clicks at the rear. Intrax have a very good after care service and charge around €100 per corner for refresh. Which only takes 5 working days and return as new all boxes up

Haven't looked back since I installed them . What are you looking for in your suspension setup, fast road or track use. KWs V3s will be good for the former but show weaknesses on track. Clubsports are closer to intrax, not sure about the rest. Actually I know someone with nitrons on a CSL and they seem to do the business.

Can I get them from Halfords?

Flatout,

Thanks for your input. I bet those Intrax are expensive.

I live in a very rural location and have some wonderful "twisties" on my doorstep, so I'm looking for a suspension set up that will have sufficient damper adjustment range to do both fast road and track use.

From my experience with setting up KWV3 on my Z3MC, and with the driving position of the Z4MC being very similar (i.e. sit just in front of the rear wheels) I like the rebound setting on the rear dampers to be pretty soft, because I've found that this setting, above all others, dictates the "ride" quality. Therefore, ideally, I'd prefer the rear dampers to have separate rebound and bump settings rather than a combined adjustment for both settings: the KW V3 and Clubsport kits have separate adjustment capability. For fast road use, I like the front suspension to be set up quite a bit firmer than the rear and I'm unsure whether the progressive springs on the front dampers with KW V3 will be stiff enough relative to the rear springs to allow me to set up the front suspension relatively firmly.

I'm presently favouring the KW Clubsports because they have genuine front coilovers with linear springs but interested to hear reports from existing users.

I am speaking with the Nitron main engineer next week, so I'll see what they can come up with.

Interested in this thread too, Exdos what's your view on the main issues with the oem suspension. Am I right in thinking you feel the rebound is too stiff and the springs too soft?

daz05 said:

Exdos what's your view on the main issues with the oem suspension. Am I right in thinking you feel the rebound is too stiff and the springs too soft?

Click to expand...

1. The front springs and dampers are way too soft, which allows the front to lift under hard acceleration and pitch heavily under braking. This means that careful setting of the static geometry all goes out of the window in hard driving conditions, because the changes in dynamic rake angle with the lifting and pitching alters the dynamic steering geometry making the steering "floaty and imprecise" under hard acceleration and a tendency to understeer when cornering after hard braking. The lifting of the front of the car also reduces stability at higher speeds because more air goes under the car than it should if the static rake angle were preserved.

2. The rear springs are too stiff under maximum rear compression and the dampers are set far too firm for rebound, which makes the back end of the car too reactive, and since the occupants sit just in front of the rear suspension, the stiff settings give a very harsh ride and it gives me pain across my shoulders at the base of my neck. This is not right!

I've obtained the spring rates from Eibach of their lowering springs for the Z4MC and they are as follows:
Front: Progressive spring, initial rate is 23N/mm (131 lbs/in) and the end rate is 34N/mm (194 lbs/in)
Rear: Progressive spring, initial rate is 70N/mm (399 lbs/in) with the end rate of 140N/mm. (799 lbs/in)
Most aftermarket adjustable suspension kits for the Z4MC have front spring rates in the region of 400 lbs/in and rear spring rates in the vicinity of 550 lbs/in, so my subjective opinion seems to be supported by the figures.

I am amazed that so many Z4MC owners seem to swap the OEM 18" wheels for 19" ones, which must make the ride worse and that so few have fitted aftermarket adjustable suspension to overcome the problem. I don't know how they can all tolerate such bad suspension and ride quality

I also think that the Z4MC would benefit from some front flippers, as on the Z3MC, rather than the tiddly little "fangs" it has.

Thanks for that, and Eibachs are meant to be around 20% stiffer than stock aren't they, at maximum anyway? I always felt they were softer around town.

I run CSLs and they offer a better ride than the OEM 18" with Conti M3s, I had them back on the car for a while and was surprised. I also remember thinking the same when I changed the first time round.

So why in your opinion has BMW made the rear rebound so hard what does it gain or was it a case of they had these dampers in the parts bin somewhere.

I read the roadster has slightly softer damping but I've never driven both to compare. Can't imagine it's that noticable, I think part of the problem is the rigidity of the car that it has no give.

daz05 said:

So why in your opinion has BMW made the rear rebound so hard what does it gain or was it a case of they had these dampers in the parts bin somewhere.

Click to expand...

I think James May might have a point that cars developed to achieve best times at The Ring end up with bad rides. I stiffen up the KWV3 dampers on my Z3MC almost to the max for bump/rebound at The Ring and it's superb set up like that there, but the same settings for the UK roads are absolutely dreadful and since the Z4MC's OEM suspension is unadjustable, I think they've settled on the wrong compromise for road use.

daz05 said:

I read the roadster has slightly softer damping but I've never driven both to compare. Can't imagine it's that noticable, I think part of the problem is the rigidity of the car that it has no give.

Click to expand...

At the time the Z3 MC was made (1998) it had the stiffest bodyshell BMW had made at the time, but they put suspension on it which was way too soft (a lovely ride though!) when driven hard, with a great propensity for excessive lateral and longitudinal bodyroll which makes the handling great fun in the dry but extremely lairy and tail-happy in the wet. An OEM Z3MC can bite you very hard in the wet! The S54 Z3MC has DSC which is particularly sensitive to changes in "yaw", and in OEM state, the DSC kicks in a lot, but once the suspension has been upgraded (springs, dampers, ARBs and bushes) there is considerably less yaw, so the DSC doesn't intervene much. When there's excessive bodyroll and weight-shifting, the static geometry settings don't apply in the dynamic situation and so the handling becomes very unpredictable.

It seems to me that in the case of the Z4MC (very similar weight to Z3MC), BMW has overcome the tendency to yaw by fitting big ARBs and improving rear traction with stiff suspension, which has prevented a tendency to excessive bodyroll and tail-happiness seen in the Z3MC, but IMO, they've not got the F/R spring balance right and they've severely compromised the quality of the ride in the process.

The OEM Z4MC handles way better than an OEM Z3MC but at the expense of the ride quality, and it can be pushed very hard too. I just don't like it though but I'm sure that with adjustable suspension with the right choice of springs the Z4MC will be transformed into a truly fantastic handling car. Personally, I'd rather spend the money that many seem to spend on CSL wheels or BBKs on the suspension, because for me, that's the worst part of the car by a very long way.

Thanks Exdos, it's rare we get into the nitty gritty on here.

We haven't had many people share their experiences of coilovers on here and most assume it will make things worse.

Already looking forward to your write up and settings when/if you make the change.

It's definitely going to happen: I can't live with the OEM suspension. I'd previously done all the research on this and ordered AST 3-way coilover suspension over 5 weeks ago, but the very poor service and lack of communication that I've been getting with my order has led me to believe that if I were to get any problems with that kit, then the aftersales experience would be even worse, so I've cancelled the order, and I'm now back at square one. A write up and experiences will follow. Until you've experienced adjustable suspension and got it set up properly, you'd never believe how it can transform the handling. 8)

exdos said:

It's definitely going to happen: I can't live with the OEM suspension. I'd previously done all the research on this and ordered AST 3-way coilover suspension over 5 weeks ago, but the very poor service and lack of communication that I've been getting with my order has led me to believe that if I were to get any problems with that kit, then the aftersales experience would be even worse, so I've cancelled the order, and I'm now back at square one. A write up and experiences will follow. Until you've experienced adjustable suspension and got it set up properly, you'd never believe how it can transform the handling. 8)

Click to expand...

excuse my lack of pm as per your request... will be getting to it tonight once mr man is asleep, got some really interesting pics, ect ect of the setup ive chosen.

now be warned the intrax is top notch no doubt BUT... and this is a big but.... they conver the rear to a coilver setup and the rear turret tops were never ever designed to withstand the force that will be placed on them, imo stick to a kit that keep the stock "type" seperate spring and damper unit....

Beedub said:

excuse my lack of pm as per your request... will be getting to it tonight once mr man is asleep, got some really interesting pics, ect ect of the setup ive chosen.

now be warned the intrax is top notch no doubt BUT... and this is a big but.... they conver the rear to a coilver setup and the rear turret tops were never ever designed to withstand the force that will be placed on them, imo stick to a kit that keep the stock "type" seperate spring and damper unit....

Click to expand...

Bee,

No worries mate! I know you have your hands full and know that you'll respond when you've got time.

I would NEVER consider a coilover set up at the rear. A couple of folk have tried this on the Z3 MC and I think they're crazy unless they've got the car fully track prepped with reinforcement of the towers as part of a full cage. Likewise, I'm not interested in aftermarket front adjustable race top mounts because the front towers NEED the rubber that's in the OEM top mounts for road use. If you can stiffen up the front suspension and with the already stiff OEM ARBs, it should be possible to get minimal lateral bodyroll during hard cornering, therefore IMO, it should be unnecessary to increase static camber on the top mounts, and if I want sharper turn-in, I'll adjust the toe settings.

Ideally you want a set up that is easily adjustable so you can switch between road use and track.

Its true that the OEM is not that great. It rolls and pitches on the track too much whilst running out out of travel at the rear on bumpy roads.

Worse of all the steering feel is not great.

Not sure Powerflex type bushes would make that much diffrence?

exdos said:

daz05 said:

Exdos what's your view on the main issues with the oem suspension. Am I right in thinking you feel the rebound is too stiff and the springs too soft?

Click to expand...

1. The front springs and dampers are way too soft, which allows the front to lift under hard acceleration and pitch heavily under braking. This means that careful setting of the static geometry all goes out of the window in hard driving conditions, because the changes in dynamic rake angle with the lifting and pitching alters the dynamic steering geometry making the steering "floaty and imprecise" under hard acceleration and a tendency to understeer when cornering after hard braking. The lifting of the front of the car also reduces stability at higher speeds because more air goes under the car than it should if the static rake angle were preserved.

Click to expand...

Got to say that's the most accurate description of whats happening to suspension and why its flawed.
I really use to notice frontend lift at speed up hill
Did consider sorting out the suspension, but it's a long road and as you've said setup is key.
A chap on here went the nitron route, but sold his car shortly after the install and never had the Chance to find out much info.

It was a good post, he's right I noticed it more last night the rear is where it's the bumpiest, doesn't help that the tyres are a lower profile either.

daz05 said:

It was a good post, he's right I noticed it more last night the rear is where it's the bumpiest, doesn't help that the tyres are a lower profile either.

Click to expand...

While the profile of the rear tyres is a lower number than the front, that number is the height expressed as a percentage of the width of the tyre. As a result the amount of tyre in the vertical plane between the road and the rim is same on the rear as it is on the front.

See here:

http://en.wikipedia.org/wiki/Tire_code#Tire_geometry

I agree though that the rear is definitely more bumpy than the front.

True but being pernickety but still 6mm less on mine and more unsprung weight than the fronts too

exdos said:

daz05 said:

I've obtained the spring rates from Eibach of their lowering springs for the Z4MC and they are as follows:
Front: Progressive spring, initial rate is 23N/mm (131 lbs/in) and the end rate is 34N/mm (194 lbs/in)
Rear: Progressive spring, initial rate is 70N/mm (399 lbs/in) with the end rate of 140N/mm. (799 lbs/in)
Most aftermarket adjustable suspension kits for the Z4MC have front spring rates in the region of 400 lbs/in and rear spring rates in the vicinity of 550 lbs/in, so my subjective opinion seems to be supported by the figures.

Click to expand...

Click to expand...

What's your opinion about the Eibach springs... Would they make the oem Z4M better of worse?

ChawenHalo said:

Ideally you want a set up that is easily adjustable so you can switch between road use and track.

Its true that the OEM is not that great. It rolls and pitches on the track too much whilst running out out of travel at the rear on bumpy roads.

Worse of all the steering feel is not great.

Not sure Powerflex type bushes would make that much diffrence?

Click to expand...

What about the Bilstein B16 PSS 10. http://www.bilstein.de/en-uk/products/sport-and-threaded-ride-high-adjustable-kits/bilstein-b16.html
You can adjust them pretty easy between soft and hard... Maybe one day I'm going to fit them. They cost 2.400euro / £1.940 my country. I don't want my car that much lower the oem and with this kit the lowering starts at -10mm...

I"m sure that the suspension on the Z4MC can be relatively easily sorted. I'm about to pull the trigger on some adjustable suspension and when it's fitted, I'll give a report on it.

I don't think lowering springs (Eibach, H&R or KW) is the answer, if I thought that they would provide the solution, I would pursue that route, since it would also be the cheapest solution too.