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BMW Z4 Suspension Options

Discussion in 'Motors' started by Phaser, 2 Oct 2014.

  1. Phaser

    Wise Guy

    Joined: 17 Mar 2004

    Posts: 1,562

    Back in June I found I had the common snapped spring issue, so I replaced the whole lot with a set of Eibach Pro springs.

    I'm really pleased with how they look, especially combined with the 20mm spacers on the rear.

    It's fine around town however when on a spirited drive on country lanes / bumpy roads, the car keeps bottoming out. I took it up to the Highlands a few weeks ago and found myself having to drive at 5/10, scared of any approaching bumps. The same trip a couple of months earlier on the standard suspension (and pre-spacers) provided no problems whatsoever.

    I thought it was the spacers at first (there's slight markings to the outer rim of the rear tyres) but from recent driving it seems as if it's more than that - sounds a lot more "bang" like rather than the grazing noise from the tyres catching if you get me.

    Bushes, droplinks etc have all been renewed and it's recently had a full Hunter alignment so there's nothing wrong there.

    So where do I go from here?

    • Have the arches rolled to see if this gets rid of the issues (probably not)
    • New set of OEM dampers and springs (I know this "works" but I'd lose the improved look, and it'd only be a matter of time before a spring snapped again)
    • Replacing the OEM dampers with some uprated ones, eg Bilstein B8 (not guaranteed to solve the problem so could be potentially be a waste of money)
    • Coilovers - this seems like the best option as I could match the current height of the Eibachs but have firmer damping so no bottoming out? I wouldn't want a harder ride though if I could get away with it

    I'm not interested in super lowz - I just want to be able to drive our roads at a decent pace without worrying I'm smashing my car to bits or having my teeth rattled out!

    Budget would probably be around £800.

    Would appreciate some opinions / advice. Thanks.
  2. pepsilol


    Joined: 26 Jun 2011

    Posts: 4,900

    Just sell the Eibachs and go and put the BMW springs back on. I'd be amazed if you had to replace the BMW spring more than once in your ownership.

    It's an everyday Z4, not a track car.
  3. sovietspybob


    Joined: 25 May 2008

    Posts: 2,835

    Location: North Wales

    I found a similar thing in our old MK3 MK5 which had lowering springs, a different make but essentially the same as Eibachs. It would bottom out over very poor roads and it did annoy me a bit, as it was the wife's car we never did anything about it but if it were my own i would have had to do something.

    Unless the car is going to see a track i wouldn't recommend coilovers as they can bit a pain on a daily and i'd bet you'd need to have them reconditioned by the same time some OEM springs snapped again so there's no longevity argument imo.
  4. alx


    Joined: 10 Aug 2003

    Posts: 6,029

    Location: Dubai, UAE

    This. Whilst the Z4 oem springs aren't bullet proof, they hardly fail every 5k miles either. They should last you more than enough time.

    Also OP, have you tried asking on z4-forum.com? They're normally very friendly/helpful and knowledgable :).
  5. Clarkey


    Joined: 18 Oct 2002

    Posts: 18,075

    Problem with those type of springs is they are typically a really soft rate about the same as stock. Great for comfort but inevitable you will run out of bump travel.
    I have very firm 'because racecar' coilovers and whilst it doesn't ever bottom out, driving at pace on a bumpy back road is out of the question, the car hops, jumps, skips, and is generally quite frightening. If you want to do that then stock suspension with compliance and long travel is going to be the way forward.
  6. HummuH1

    Wise Guy

    Joined: 28 Mar 2007

    Posts: 2,433

    Location: Edinburgh

    What Z4 and what age?

    I'd be very surprised if it's bottoming out because of the Eibachs, the drop is not that aggressive. They are the one make of springs, particularly on BMW's, that are designed and rated to work with OEM dampers, particularly ///M and MSport spec dampers. Not sure if it's still the case, but if you bought springs from AC Schnitzer, they were Eibach Pro springs.

    What Clarkey says is right, you will get "bounce" if springs and dampers aren't properly matched with ride height given the state of our roads.

    If there's any scrub marks on the outside of your tyres after lowering, your offset is wrong. Change to smaller spacers and bolts or get your arches rolled. I'd suggest the former rather than the latter. Reducing offset by 20mm deviates quite a bit away from design spec, 40mm across the axle, not ideal.
  7. Will


    Joined: 18 Oct 2002

    Posts: 4,432

    Location: Halesowen

    My mx5 had Eibach springs on it when I got it and it was the same, the back end felt very unsettled and bouncy as it would run out of bump travel. You could get it to scrape in the middle over bigger bumps too, bit alarming at times.

    I went to coilovers and it solved the problem, the spring rates are fairly low and the damping can be adjusted. They are also a design with an adjustable spring platform so you don't preloaded the springs too much by being lowered. The ride is a bit firmer than a standard mx5 but definitely better than it was with just the springs, and the damping is far superior .

    Everyone saying 'coilovers are crap on a road car' needs to understand that the design means a coilovers can be anything from unbearable to better than stock, it's a case of buying something with suitable spring rates, adjustable spring perch and adjustable damping. It might need some setting up but perfectly usable on the road.

    To solve the OPs issue... Go back to standard springs, or be prepared to spend some decent money on coilovers. KW v3, Bilstein B16 or similar... Wont get these for your budget though.
  8. Clarkey


    Joined: 18 Oct 2002

    Posts: 18,075

    The Kw clubsport on Gibbos M3 are fantastic, the price tag makes me weep though.
  9. Usel

    Wise Guy

    Joined: 14 Jan 2003

    Posts: 1,081

    I have an 04 Z4 on 17" stock rims with stock springs and 20mm rear and 15mm front and get no bangs, knocks or anything.
  10. RichIbizaSport

    Wise Guy

    Joined: 29 Dec 2007

    Posts: 1,415

    Location: London

    I had an 07 z4 coupe, replaced both springs after around 2 weeks of ownership (1 had snapped). 3 years later (30-40k miles) they were still fine when I sold the car.

    I vote for a return to OEM.
  11. theone8181


    Joined: 27 Mar 2013

    Posts: 4,455

    What are you guys classing as 'coilovers' are they not standard parts on most cars with the spring on the damper or is it for cars that dont have that but can be converted.
  12. Clarkey


    Joined: 18 Oct 2002

    Posts: 18,075

    Would have thought it's pretty obvious, ones with tapped shock for height adjustment.