Your experiences of aftermarket suspension on the Z4 MC

hmmm definitely respect you choice john, ive rode in a acs shod vehicle and i found it just to soft, im sure you'll be pleased and i agree with you, the difference to with a new coilover setup and proper setup is night and day, the ARBs are more than thick enough imo..... we just need better damping and a better spring, throw in soem choice adjustments this car handles like a dream.......

As Ever their are allways compromises.
 
exdos said:
ga41 said:
Might your imprecise steering be cause by worn bushings then? :?
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No. When I fitted the Strongstrut to my Z3MC it only had about 8k miles on the clock, and the difference it made was considerable. My Z4MC has only 25k miles on the clock and is as tight as a drum.

I know many people think that a strutbrace has a placebo effect,
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Not at all, I noticed a big difference when I installed mine.

Frontend was more controlled on bumpy roads and felt more direct generally, not sure the strong strut would be any better than BMW, it too is very light and a lot cheaper.
 
I made a start fitting the ACS Racing suspension today. I decided I would fit the rear suspension first because the rear isn't height adjustable but gives a 10mm drop on OEM, and so when I fit the front, I'll be able to adjust accordingly. I was expecting that removing the rear trim to access the top mounts was going to be a pain in the 4r5e, but it proved to be much easier once I'd worked it out.

When I removed the rear dampers I measured the wire thickness of OEM v ACS, and OEM is 19mm and ACS is 16mm, so clearly the relative spring rate of the ACS is quite a bit softer than OEM.

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For my Z3MC I've fitted Rogue top mounts at the rear so that you can remove the dampers from inside the rear wheel arch without having to remove all the trim in the back, however, I've since learned of a much cheaper alternative. You use a Z3 Roadster strengthening ring and tack weld the bolts from OEM top mounts onto them and then install from above. This also gives additional strengthening to the body at the position of the rear top mount. I've fitted a paper gasket under the attachment and on top of the OEM top mount, to prevent any noises.

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I set the rear dampers to position 8 (9 being the softest) and did a test drive and I was pleased that there were no noises and rattles, but most of all, the ride is exactly as I hoped it would be, COMFORTABLE without any jarring to my neck and shoulders. In fact, at position 8 with the OEM front suspension (too soft) there is increased body roll, which shows that the OEM rear suspension is doing the Lion's share of resisting body roll, whereas, I prefer the front suspension to do this task. :D

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Looks good. I'm waiting to see if you can improve the handling as well as softening the ride for your tired old bones :P
 
awesome work john.... did you pick this kit up from pistonheads??? their was a lightly used one going for £1400?????
 
BMWZ4MC said:
Looks good. I'm waiting to see if you can improve the handling as well as softening the ride for your tired old bones :P
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Every mod I've ever done, I've always done them one step at a time and tested each one so that I know precisely what the effects are. You just can't beat first hand experience. I have my own "Ring" test route on my doorstep. I'm absolutely sure that I can improve the handling and ride of my Z4MC with the kit that I've bought. It was a joy to feel the car with a decent ride this afternoon.
 
Beedub said:
awesome work john.... did you pick this kit up from pistonheads??? their was a lightly used one going for £1400?????
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Yes. It's been for sale for over 2 months and I can't believe that no one else had snapped it up. It's like brand new and I've got it for a fraction of the price. 8) It's real quality stuff.
 
exdos said:
Beedub said:
awesome work john.... did you pick this kit up from pistonheads??? their was a lightly used one going for £1400?????
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Yes. It's been for sale for over 2 months and I can't believe that no one else had snapped it up. It's like brand new and I've got it for a fraction of the price. 8) It's real quality stuff.
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Good snatch I noticed it a long time ago ;-)
 
I finished installing the ACS Racing suspension today and I took a few more photos as below.

The front OEM springs are 11mm diameter wire and the ACS front springs are 14mm. Using the spring rate calculator here: http://www.pontiacracing.net/js_coil_spring_rate.htm as a very rough "ballpark" of the spring rates, and the wire diameters of the OEM v ACS springs you can see that the difference between the two different set ups. If we just change the wire diameter and keep all the other parameters fixed then this gives the front to rear spring rate ratios as below:
OEM F=11mm R=19mm Spring rate ratio F:R = 1 : 11
ACS F=14mm R=16mm Spring rate ratio F:R = 1.9 : 1
Although these figures are not correct, because the number of coils and coil diameters are different, you can still see that the diameter of the wire of the springs has a very significant part to play in spring rate, and that the ACS Racing suspension increases the front spring rate and lowers the rear spring rate, relative to OEM suspension. In reality, I understand that the Spring rate ratio of the OEM suspension is in the order of 1 : 5, whereas, the ACS Racing suspension is in the order of 1 : 1.2. Some difference!

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This photo shows the amount of droop when the nearside front wheel is completely unsupported. The relatively shorter total movement in suspension travel, compared to OEM, will considerably reduce body roll, pitching and lifting at the front of the car.

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This photo shows the StrongStrut strutbrace installed.


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I now need to do some testing with different damper settings and I will report my findings in due course.
 
Exdos great write up and gr8 colour .

I note you have both z3 and 4 which do you you like most now your z4 is getting closer to how you want it?
I love my z4 bit missing the quirkiness of my z3m
 
Ojiako, thanks! :thumbsup:

My Z3MC will always be my favourite, for many different reasons, but I'm definitely warming to the Z4MC. I certainly couldn't live with OEM suspension on a Z4MC though, because it's just all wrong. It was always my intention to do some selective mods as soon as I got the car and it's great to experience the transformation. :D
 
exdos said:
Ojiako, thanks! :thumbsup:

My Z3MC will always be my favourite, for many different reasons, but I'm definitely warming to the Z4MC. I certainly couldn't live with OEM suspension on a Z4MC though, because it's just all wrong. It was always my intention to do some selective mods as soon as I got the car and it's great to experience the transformation. :D
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couldnt agree ore... the transformation is the best bit and tweaking and setting up... especially when you get a big change.... one of my biggest changes had to be the brakes..... The brakes have made such a difference to the confidence i have in the car..... i was happy with the stock suspension until the car reached silly power, then it really became apparent how much setting up and fine tuning with new components was needed....

love that your doing john..... keep it up, ive really enjoyed your input on the forum, looking forward to you popping over so i can show you my idea of a cool z4m.
 
exdos, Looking good, wow much have you dropped the car from OEM and are you going to corner weight / geo the car with the new suspension on there?
 
Beedub said:
love that your doing john..... keep it up, ive really enjoyed your input on the forum, looking forward to you popping over so i can show you my idea of a cool z4m.
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:thumbsup: I very much enjoy doing all the research and studying that goes with the sort of modding that I do, I know some others like reading about it too. 8)


RedUn said:
exdos, Looking good, wow much have you dropped the car from OEM and are you going to corner weight / geo the car with the new suspension on there?
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I've followed the ACS fitting instructions for the initial set up and I've ended up with the front at 660mm and the rear at 670mm (floor to top of wheel arch). The rear isn't height adjustable but the front is, so I've adjusted the height a little on the front O/S to account for the loading with me in the driving seat. I want to drive with those heights for a while before I decide whether to lower the front a tad more or not: I'm more bothered with the rake angle rather than whether the wheels fill the arches.

The lowering of the front increased the negative camber visually, but when I checked the toe angle, it had also increased the toe-in a fair bit too, which accentuated the negative camber appearance. I've reset the toe yesterday: I was expecting it to be impossible to turn the tie rods, because they are invariably seized and need heating, but I'd sprayed penetrating fluid on them a few weeks ago, in readiness, and it must've worked well! :D I like zero toe on my cars.

I seem to spend a fair bit of time tinkering with set ups, so I do my own geometry with a relatively simple DIY system that I've devised using lengths of straight-edged angle aluminium, a tape measure and a marker.

I didn't want to be forced into using spacers just to fit an aftermarket suspension and these aren't required for the ACS Racing suspension. However, I shall now consider fitting spacers for the benefit that they can give to the handling and I'm also considering uprating the front ARB too.
 
I like 0 toe front as well but thinking of trying some toe out next time i have it aligned. Don't ask me figures, i haven't researched it yet.
 
ga41 said:
I like 0 toe front as well but thinking of trying some toe out next time i have it aligned. Don't ask me figures, i haven't researched it yet.
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You'll find that toe out makes the steering "exciting", to say the least!
 
If you do updated arbs John be warned you must look at reinforcements on the front chassis ,this is a known area to fail with beefed up arbs.
 
Beedub said:
If you do updated arbs John be warned you must look at reinforcements on the front chassis ,this is a known area to fail with beefed up arbs.
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Thanks for that. :thumbsup: It's also a weak spot on the Z3MC, particularly at the rear end where the boot floor gets ripped apart :o

Is there a "how to" strengthen the Z4 chassis for ARBs anywhere?
 
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