Z4M R springs

Z

Z4M-2006

Elite
 High Peak,Derbyshire.
I want to change the springs on the car..

The usual suspects are H&R and Eibach.....

It seems the H&R drop the car 25mm,which is too low. Eibach seem to be 10mm rear and 20mm front.

Do any of the aftermarket spring makers do a standard ride height spring..?

I just want the standard springs off as they are way to hard at the rear..

Cheers
 
Lowering it won't really help you with the stiffness you would need to get a coilovers kit to change the stiffness of the damping at the rear.

There are at least 4 spring options, BMW, Unipart, Eibach and H&R. Eibachs although stiffer have been reported to soften things slightly at lower speed but nothing hugely noticeable. H&Rs as you say go even lower and I suspect will be even stiffer than stock.
 
I looked into replacing the springs only but found there was no alternative to fitting an aftermarket suspension. I therefore bought an adjustable set up so that I could get both the ride and handling that I wanted.
 
Exdos...

Just the man..

Im not gonna spend £2000 on the suspension,that isnt really an option.....lol..

I was reading your write up about the high spring rate on the rear,and was thinking that fitting "something" aftermarket it may ease the harshness..?
 
The rear springs have middle coils of 19mm diameter - that's stiff! However the front springs are way too soft, so if you were to replace the rear springs for something softer, the car would be worse for pitching and squatting and the handling would be worse.

Your best bet might be to contact a spring manufacturer (Sheffield?) to see what might be available to fit the car so that you can have stiffer front springs and softer rear springs in the order of 400lbs/inch F:R
 
You wouldn't happen to know the spring rates of Eibachs or H&R's would you?

I would sacrifice going a little lower if I could get a more acceptable spring rate
 
Z4M-2006 said:
You wouldn't happen to know the spring rates of Eibachs or H&R's would you?

I would sacrifice going a little lower if I could get a more acceptable spring rate
Click to expand...

A few months ago I got in touch with Eibach and this is the information they gave me for their spring rates for the Z4MC, and theirs are supposed to be about 15% stiffer than OEM;
Front: Progressive spring, initial rate is 23N/mm and the end rate is 34N/mm
Rear: Progressive spring, initial rate is 70N/mm with the end rate of 140N/mm.

Also, this is the difference in wire thickness (maximum) between OEM and the springs of my ACS suspension.
OEM F=11mm R=19mm
ACS F=14mm R=16mm

It's a shame that very few Z4M owners in the UK seem to have done any proper modding of these cars. There's probably a "work around" of fitting various different E46 springs to achieve a decent result, but this would be all trial and error without knowing the actual spring rates. However, without knowing this information, wire thickness of the springs gives a pretty good indication of the likely spring rate. Perhaps an enquiry to a specialist BMW breakers, such as FAB Direct, could help you?

Hope this helps.
 
Yea...

Fab arent too far away...i may ask..

I find it unusual that aftermarket manufacturers wish to stiffen the rear end of the Z4M even more... What would be the point?
 
Z4M-2006 said:
Yea...

Fab arent too far away...i may ask..

I find it unusual that aftermarket manufacturers wish to stiffen the rear end of the Z4M even more... What would be the point?
Click to expand...

Maybe they have shares in chiropractors :D
 
Z4M-2006 said:
I find it unusual that aftermarket manufacturers wish to stiffen the rear end of the Z4M even more... What would be the point?
Click to expand...

If you're lowering the car, then the effective stroke length of the damper pistons becomes shorter, therefore the springs need to be stiffer to ensure that the pistons can still operate , but over a shorter working range without coil-binding and riding on the bump stops all the time.

In comparison, the manufacturers of aftermarket full suspension kits can use shorter dampers which are designed to operate over the complete range of lowering on the height adjusters, if you see what I mean.
 
exdos, hi, thanks for your recent advice on various topics, really helpful, what set up have you changed to,and has it improved the ride without affecting the handling, that bang bang bang over rough tarmac is that any better,as it is annoying i find, but i wouldnt want any more body roll, i know hteres always a trade off. thanks again. :driving:
 
mad4slalom said:
exdos, hi, thanks for your recent advice on various topics, really helpful, what set up have you changed to,and has it improved the ride without affecting the handling, that bang bang bang over rough tarmac is that any better,as it is annoying i find, but i wouldnt want any more body roll, i know hteres always a trade off. thanks again. :driving:
Click to expand...

I have fitted ACS Racing Suspension (adjustable), H&R ARBs (30mm front, 25mm rear), Rear trailing arm bush limiter kit and 10mm spacers all round. I have set up the car: Front -1.3 camber 0 toe, Rear -0.9 camber 0 toe.

The ride in a car such as the Z4MC, where you are sitting over the rear suspension, is essentially determined by the stiffness of the rear suspension. The ACS rear springs are of 16mm diameter wire (KWV3 will be similar) whereas OEM is 19mm, so the ACS springs will inherently make the ride much more compliant and then this can be fine-tuned by adjusting the damper settings, from sedan-like soft to very firm.

I just couldn't live with a Z4MC with OEM suspension and I knew this before I bought mine in March and I always intended do a suspension upgrade ASAP. The ride has been completely transformed and the handling is superb with virtually no lifting on acceleration and pitching under braking. For me it's been a win-win for both ride and handling. There are 9 settings on the dampers for combined rebound and bump/compression adjustment and I presently have them set at 5 on the fronts and 6 on the rear, for driving on fast A & B roads, but for track use, I expect that I will be down to 2/3 for some serious stiffness.

There have been absolutely no downsides apart from the cost, but for me, that's been money very well spent. :thumbsup:

I'd already been through this process with my Z3MC so I knew what I was doing and how to do it from the outset with my Z4MC.
 
john did you use the rear csl H n R bar can you confirm that its a direct fit??...?? im alittle concerned the front wont fit because ive been told the clubsport setup changes the position slightly of the drop link.... how true that is i dont know, as techically i could just use adjustable drop links. BUT thinking logically im wondering if im being misinformed. The clubsport kit came with its own drop links, that look shorter to me??

As youve done this on the z3m, any experience with aftermarket ARB and kw bits would be helpful.
 
Byron,

The H&R ARB kit is described as the E46 M3 kit, the CSL already comes with a 30mm front ARB. The rear H&R ARB IS a direct fit. The front is also a direct fit, but you need to fit a pair of shims under the ARB brackets just to improve clearance of part of the chassis (I've described this elsewhere).

Yes I do have KWV3 and H&R ARBs on my Z3MC and KW supply shorter front drop links, but I replaced them with Whiteline adjustable drop links, which made a noticeable difference because I managed to set them up without preload on the ARB.

So, I was looking for some adjustable drop links to use with the H&R ARB that I've fitted to the Z4MC and I came across some that I'd not seen before. These use the OEM type sealed ends which screw into an adjustable threaded tube. The kit comes with three different pairs of adjustable tubes so that you can use these with both OEM dampers or with KWV3, which require shorter droplinks. I obtained them through this ebay seller: http://stores.ebay.co.uk/Rudie-Mods

At £49.95 these have to be the cheapest adjustable drop links around. I bought a set and have fitted them as below. They're a bit heavier than OEM but they look as though they're made to last! One of the advantage of these over adjustable droplinks with rose joints is that the ends are completely sealed, not to mention they're about half the price! The increase in weight doesn't seem to affect the handling at all. I would expect the middle-sized rod would be the one that would fit your KW Clubsports.

Setting up the drop-links can be a bit tricky but there's a "sweet spot" that you can actually feel when your adjusting them, and you need to fix them at that point.


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