Z4M - Suspension Help

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InterlagosZ4MR

Member
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...?
 
Is the B12 height-adjustable? Has it been set too low?

I have the B16 kit and love it, and have no problems on Welsh hoons, Peaks & Dales runs, Scottish outing, or Ring trips.

I specifically research/wanted a compliant ride as it was my daily, doing 25k miles a year. I also specifically asked for the car to be lowered no more than 1cm to avoid extra harshness and damage from speed bumps...although it seems to come back from my suspension service every year looking slightly lower, so will have to ave a word with him about that :headbang:

Where are you based? Maybe a couple of trips in cars equipped with different t suspensions options will help you make up your mind?
 
Do you know any other Forum members with a Z4M that you can meet up with and have a drive in one another's car. I am not saying there's anything wrong with your car but someone else's opinion could help.
 
InterlagosZ4MR said:
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...?
Click to expand...
Sell the b12 kit on here and get some adjustable coilovers?
 
Lynchy said:
Do you know any other Forum members with a Z4M that you can meet up with and have a drive in one another's car. I am not saying there's anything wrong with your car but someone else's opinion could help.
Click to expand...

Great shout, might be worth posting your general location and meeting up with a forum member. A second set of eyes (or cheeks in this case) can be helpful. Interesting personally as I'm thinking about changing my suspension to a B12 kit.
 
I find the same with B6s and eibachs which is essentially the b12. Can't remember if it was the same with eibachs and oem dampers, think it was. It improved the ride on normal bumps but still rubbish on large pot holes. Was oem any better then? Maybe H&R springs would be better and the eibachs are the problem.
 
bmwaddict said:
Lynchy said:
Do you know any other Forum members with a Z4M that you can meet up with and have a drive in one another's car. I am not saying there's anything wrong with your car but someone else's opinion could help.
Click to expand...

Great shout, might be worth posting your general location and meeting up with a forum member. A second set of eyes (or cheeks in this case) can be helpful. Interesting personally as I'm thinking about changing my suspension to a B12 kit.
Click to expand...

How do you find the H&Rs?
 
Heres how mine sits. As you can see not much clearance at the front. Think the Z4m is just generally crap over large potholes. Not to bad otherwise
duyvd9D.jpg

XXmyptC.jpg
 
mc5 said:
bmwaddict said:
Lynchy said:
Do you know any other Forum members with a Z4M that you can meet up with and have a drive in one another's car. I am not saying there's anything wrong with your car but someone else's opinion could help.
Click to expand...

Great shout, might be worth posting your general location and meeting up with a forum member. A second set of eyes (or cheeks in this case) can be helpful. Interesting personally as I'm thinking about changing my suspension to a B12 kit.
Click to expand...

How do you find the H&Rs?
Click to expand...

Nice, but a bit too harsh for the roads I drive on, they're lower than the Eibachs you get in the B12 kit.
 
bmwaddict said:
mc5 said:
bmwaddict said:
Great shout, might be worth posting your general location and meeting up with a forum member. A second set of eyes (or cheeks in this case) can be helpful. Interesting personally as I'm thinking about changing my suspension to a B12 kit.
Click to expand...

How do you find the H&Rs?
Click to expand...

Nice, but a bit too harsh for the roads I drive on, they're lower than the Eibachs you get in the B12 kit.
Click to expand...

Still on the original shockers ?
 
InterlagosZ4MR said:
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...?
Click to expand...

If you want it properly sorted you will have to get some coilovers, I'd recommend some KWs but the Bilsteins get great reviews on here.

Other than that, what tyres are you running and what pressures?

Don't give up just yet :thumbsup:
 
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 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).
 
mmm-five said:
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).
Click to expand...

+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.
 
So how does it handle pot holes on your fancy KW v3. Does it absorb them or make a crashing thump
 
mc5 said:
So how does it handle pot holes on your fancy KW v3. Does it absorb them or make a crashing thump
Click to expand...

Hah, I just edited to add a point on that. Really good, yeah - reminded me of my friend’s 911 is the way it just “thunked” in and out of dips in the road when I first drove it. A friend with a 3.0si commented on this as well in a back-to-back comparison.
 
Wait a second. How big are these potholes and why are you driving over them? :?
 
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