Z4M - Suspension Help

[mc5]

I never spot them lol. Big drain covers can be an issue to. Guess coilovers could be the only answer. 90% of the time its fine on the bilsteins its the odd time thatcan send a thud through front that be annoying. Never had this in Porsches, m3s or s2000s. Luckily the rest of the car makes up for it

 

[RedUn]

I don’t think you’ll get it anywhere near as compliant as the others you’ve mentioned, except maybe close to the M3.

Even compared to the M3, I think you’re finding a combination of issues really:

• higher torsional rigidity
• shorter wheelbase
• sitting right over the rear wheels
• thinly-cushioned seats

My mates CSL with Recaro buckets feels more compliant than my Z4MC, and is much more fun to drive at 9/10ths on a bumpy B-road than a standard Z4MC, and I’d have gone for one of them if I hadn’t been planning on putting 150k miles on it.

Coversely, when I tried an e9x M3, it felt like a blancmange compared to the Z4MC - and seemed to take a long time to settle into a steady position on corners, so you had to turn earlier than you’d expect - felt more like my lardy e34 M5, which is both a good thing (for an autobahn stormer) and a bad thing (for a fast-road/track sports coupe).

+1

It’s a fundamentally unsettling car to drive. How much of that is perceived due to the layout and how much is caused by the chassis and suspension set up, I’m not sure.

The KWs I have definitely sort out the crash/unrefined behaviour, but the rear is still very lively.

What geo are you running? Have you fettled the rtab in anyway?

I'm running clubsports and arbs on a fairly aggressive setup and I've got loads of grip at the rear, infact probably too much.

Also consider corner weighting, makes the car so much smoother once its been properly done with a geo, the guys I use are a porsche specialists and they were impressed with the road manners and ride compared to the porsches they do with a similar setup.

I know Beedub will say the same, once you properly sort the zed it really is very very good!

P. S. It'll never ride like a lotus it's twice the weight!

 

[RedUn]

Thanks for all replies. Running OEM wheels with new Pilot Sports. I guess coilevers are the answer but that’s another £2.5k investment on top of the £1k I’ve just spent on the B12. As I mentioned, I’ve had the Z for 4 (nearly 5) years and have had Elises, Caterhams and numerous M3s... and just want it even 50% as compliant as any of those...

Answered these in the wrong order but something else that helps with the ride is spacers, they take the edge of the crashyness.

 

[Pures3]

Take a look at this old thread regarding RTABs. I’m putting the turners on mine - hope it sorts out the feeling of total lack of control on twisty B roads!

https://z4-forum.com/forum/viewtopic.php?t=62834

 

[gazpat]

Hi,
As per my previous posts on this subject (not sure how to link), Nitron coilovers all round specced for road use, standard (factory) ride height, full Geo set up by Centre Gravity (who know their stuff), job done. Not cheap I agree, but probably the best performance mod you'll ever make to this car....

 

[MrPT]

+1

It’s a fundamentally unsettling car to drive. How much of that is perceived due to the layout and how much is caused by the chassis and suspension set up, I’m not sure.

The KWs I have definitely sort out the crash/unrefined behaviour, but the rear is still very lively.

What geo are you running? Have you fettled the rtab in anyway?

I'm running clubsports and arbs on a fairly aggressive setup and I've got loads of grip at the rear, infact probably too much.

Also consider corner weighting, makes the car so much smoother once its been properly done with a geo, the guys I use are a porsche specialists and they were impressed with the road manners and ride compared to the porsches they do with a similar setup.

I know Beedub will say the same, once you properly sort the zed it really is very very good!

P. S. It'll never ride like a lotus it's twice the weight!

Yeah. It needs higher spring rates and has less travel to work with than Norfolk’s finest. Especially at the rear.

Geo was stock but for a setup 1.5cm lower than I am currently running. Corner weighting was done and there’s a bit of an offset in suspension heights because of that. RTABs are visually ok but I’m going to do a refresh of all bushes soon, fit limiters and get the geo done to my own liking. I recently pulled the camber pins and went to max -ve (which has been great) but the front end is getting a bit woolly. ARB bushes in particular look pretty tired.

Don’t get me wrong, I love the way the car handles, but it doesn’t feel as composed as other sports cars I’ve driven. Spent about an hour of track time in a C63S recently and it came a lot closer to the Z4M for excitement than the Porsches I’ve driven. Really impressed by it. It’s that combo of slightly mad engine and difficulty putting the power down that’s so addictive, although to be fair it has 700Nm.

 

[RedUn]

A mate had a c63, awesome car, properly rowdy aren't they :evil:

Like you say the geo probably won't help, the OEM geo gives a very dull feeling, be good to get that sorted out 8)

The front shouldn't be woolly at all once that's done, if it is somethings worn somewhere? Maybe the arb bushes like you say? I do recommend the h&r arbs mind, really tighten the car up and work well with the kws

 

[Nev]

I've not that long ago fitted B6's with Eibachs all round and the ride is much better but still crashy going over any form of pothole, which to be fair are everywhere up north! Since my upgrade to the suspension, as all my corners were shot and in need of replacing, the car feels so much more planted on the road. Very good fun thrashing around the lake district recently!

I've been replacing bushings all over the place but the harshness I've found is now mainly at the rear. I've been messing around with the rear top mounts a bit. Changed them to poly bushes, but found them waaay too harsh so i've gone back to nearly OEM with Meyle HD top mounts. The tightness of the top nut on the rear top mounts seems to make quite a difference too. Too tight and its banging going over any stone in the road, too loose and its clanging a bit! As I said before, the roads up here are shite for it so its about getting a balance.

 

[ph001]

Tyre pressure do make a big difference so I would definitely experiment taking them down as low as 30psi rear, 28psi front (if you haven't already).

 

[autobahner]

Thanks for all replies. Running OEM wheels with new Pilot Sports. I guess coilevers are the answer but that’s another £2.5k investment on top of the £1k I’ve just spent on the B12. As I mentioned, I’ve had the Z for 4 (nearly 5) years and have had Elises, Caterhams and numerous M3s... and just want it even 50% as compliant as any of those...

I've had 3 e46 M3 and all were far nicer to drive than the Z4M I had for a short time. Handling as you described and I felt completely detached from the road, the opposite to the M3. Sold and looking for another M3 :wink:

 

[TomK]

I've had 3 e46 M3 and all were far nicer to drive than the Z4M I had for a short time. Handling as you described and I felt completely detached from the road, the opposite to the M3. Sold and looking for another M3 :wink:

Sounds like you had a duff one, shame

 

[Muckinonthesofa]

So I'm at my wits' end with what to do with the suspension on my Z4M... and it's now unloved, forlorn and undriveable.

The car has done 42,000 miles on original suspension and like many others find it too hard, imprecise, floaty and a bit understeery...
On the advice of this and other forums I put on an Bilstein B12 kit on it that has ruined the car. It's too low, but worse, it's trashy to the point where it just feels broken and the smallest pothole makes it feel like theres no suspension. It's impossible to drive fast as the smallest imperfection will unbalance the car and make it unpredictable. The crashyness is awful - and frankly I loathe the car. Yes, it's been back and checked, and yes I've had an alignment done...

All I want is for the Z to be as good as any of my M3s. I never want to do track days - it's simply for fast B and A roads, and is solely a weekend car.

I'm really not sure what to do - I'm not going to persevere with the B12 kit any more and am going to ditch it on eBay to some other poor unsuspecting M owner and put the original suspension back on. Short of selling the car (which I'll probably do as after 4 years I've had enough) - any last resorts as regards suspension fixes...?

After reading about your problems with the B12 kit I actually started doubting myself as my car has been sorned since December. I could not believe someone else had such an opposite experience to me.

With my car now back on the road after it's winter lay off, I'm honestly convinced you've been sold a duff kit or the fitting was incorrect in some way. My car feels great with this kit, the quality of the damping is massively improved. It will thud over potholes but it did this before to a slightly lesser extent.

I hope you've got it sorted and didn't sell it?

 

[InterlagosZ4MR]

Yes sorted thanks. Got rid of Eibachs and went back to new OEM springs but with Bilsteins, and geo settings half way between CSL and factory. Much better than before and certainly a million times better than Eibachs that ruined the car (for me!)

 

[InterlagosZ4MR]

Yes sorted thanks. Got rid of Eibachs and went back to new OEM springs but with Bilsteins, and geo settings half way between CSL and factory. Much better than before and certainly a million times better than Eibachs that ruined the car (for me!)

PS the issue was that the Eibachs meant it was on its bump stops all the time and b) far too hard. Spoke to Kevin Bird who recommended current set up - and agreed along with BMW technicians I spoke to that Zs should never be lowered...

 

[dgm]

I’m glad the change to OEM springs worked out with the Bilstein B6 shocks as that’s the route I’m going to go down shortly, I have no interest in lowering the car at all. Do you have a copy of your geo set up that you could post, I’d be keen to give that a go?

 

[InterlagosZ4MR]

I’m glad the change to OEM springs worked out with the Bilstein B6 shocks as that’s the route I’m going to go down shortly, I have no interest in lowering the car at all. Do you have a copy of your geo set up that you could post, I’d be keen to give that a go?

I don’t sadly. I had a long conversation about what I wanted with a technician at my main BMW dealer - more turn in than factory, not as agressive as CSL and he got it spot on.

 

[dgm]

I’m glad the change to OEM springs worked out with the Bilstein B6 shocks as that’s the route I’m going to go down shortly, I have no interest in lowering the car at all. Do you have a copy of your geo set up that you could post, I’d be keen to give that a go?

I don’t sadly. I had a long conversation about what I wanted with a technician at my main BMW dealer - more turn in than factory, not as agressive as CSL and he got it spot on.

Thanks anyway, I’ll maybe have to do something similar.

 

[abar121]

Yes sorted thanks. Got rid of Eibachs and went back to new OEM springs but with Bilsteins, and geo settings half way between CSL and factory. Much better than before and certainly a million times better than Eibachs that ruined the car (for me!)

PS the issue was that the Eibachs meant it was on its bump stops all the time and b) far too hard. Spoke to Kevin Bird who recommended current set up - and agreed along with BMW technicians I spoke to that Zs should never be lowered...

That's great to hear. Yes, spot on advice from Birds as usual.

 

[99ron]

There have been several threads about the Z4M B12 kit recently and I reckon this old thread is the answer. Ditch Eibachs for standard springs. I've perhaps only done a couple of thousand miles on mine but I've had enough of the crashing over potholes. Dropped gullies across the road are the worse. Makes me cringe in pain in sympathy with the car.
Standard springs then I reckon. B12 kit really isn't fit for purpose. Just gotta find some budget now...

 

[Mr Tidy]

I've spoken to a couple of M owners who have fitted Eibach springs then removed them again.

My car came fitted with H & R coli-overs and they are very crashy too.

Last year I was lucky enough to get a ride in a 20K mile MC on OE suspension and compared to my car it was like a magic carpet ride, so if/when I change I'll stick to OE springs - not sure about dampers though.

But as my H & Rs have only done about 20K I can't get my head around swapping them yet, even though I often also cringe quite often when I hit a bump.