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Suspension help

Discussion in 'Motors' started by Kingy, 10 May 2010.

  1. Kingy

    Mobster

    Joined: 18 Oct 2002

    Posts: 3,403

    Location: Leicester

    o/

    My Z4 needs some suspension work doing, but I'm not sure if I should be looking to get more done than is needed right away while the garage has got the car on the ramp etc?

    I'm told that the front wishbones and rear bushes have play, and need replacing. I figure that if the front wishbones needs doing, then why don't the rears? Same point regarding the front bushes if the rears need replacing?

    Trouble is, I've never know anything about suspension, and this only gets worse when people start talking about shocks, dampers and struts (somebody told me that these are the same thing?) and springs?

    Basically, the car has done 90k now, and I don't often get time to get work done on it, so if there's anything obvious that's worth doing without breaking the bank, then it'd be good to do it. Nobody I've spoken to so far seems to understand what I'm talking about though... :o(

    I'd like the handling to be good, but I don't really want to compromise on ride quality as I do 30k year. Having the OEM components refreshed seemed like a good starting point before I started thinking about ARBs etc...

    Can anyone join the dots together to draw a pretty picture I can understand please? ;):p
     
  2. Matt82

    Capodecina

    Joined: 13 Mar 2004

    Posts: 16,600

    thats a damper. that controls the movement of the spring. stops the car going boing!
    No hotlinking!


    here is a spring
    No hotlinking!


    thats all there is to it (unless you include the anti roll bar)

    the spring sits on the damper. the damper controls the spring.

    those two combined make a "strut". the strut goes between the body of the car and the wishbone

    the wishbone connects to the car via bushes. those often need to be replaced

    if they say the bushes are dead, just replace the bushes. its well worth doing
     
  3. aproctor

    PermaBanned

    Joined: 26 Apr 2008

    Posts: 4,078

    Location: Lincolnshire

    Suspension is very objective and everyone will have a different opinion, the opinion is usually whatever they have bought as they have only tried a tired OEM setup and a new set.

    There are different types of suspension, coilover (which comes in fully adjustable form as well in most cases), macpherson struts and leaf.

    Your BMW will likely have one of the former.

    If you are happy with OEM that is what i would go for, but whatever you buy try it first and get a dyno of the shocks.

    Dampers/shocks are the same thing and struts are found on macpherson strut setups and these use a damper.

    In terms of bushes, the fronts go first as they are the ones used in the steering and are subject to the most crud etc on the road iirc.

    If you go the polybush route check the type (self lubing or not) and the durometer (how hard they are). Again most people rave about "poly bushes" but again most that do have tried knacked OEM and the new ones.

    On an MX5 the stock bushes are 55 durometer and some polys are 75, 95 etc and make the ride a bit jarring.

    If there is a handling characteristic you want to improve i would have a read as there is lots of info and products availible, but with so many variables (each with pros and cons) be sure what you are after.
     
  4. Sin_Chase

    Capodecina

    Joined: 13 Jan 2004

    Posts: 20,580

    Get the parts you need replacing in OEM form unless you want to spend the time, money and research putting after market kit on with specialists.

    Springs/dampers should be replaced in pairs.
     
  5. aproctor

    PermaBanned

    Joined: 26 Apr 2008

    Posts: 4,078

    Location: Lincolnshire

    Nice simple introduction and that is what most people neglect when they start looking for uprated parts.

    There is a lot more to it than that though (if your going down the aftermarket route) such as bump and rebound settings, spring poundage, spring length.

    Then the ARBs are another story.

    As i said stick to OEM unless there is something you want to improve e.g. you can reduce body roll with springs, ARBs or a combination of the two.

    The springs with give a firmer ride, but ARBS will allow a softer spring and kick in when cornering, the downside is that bodyroll lets you know how far you can push that car without spinning out.

    Spot on.
     
  6. aproctor

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    Joined: 26 Apr 2008

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    Location: Lincolnshire

    Get a decent 4 wheel alignment as well when it is done.
     
  7. Matt82

    Capodecina

    Joined: 13 Mar 2004

    Posts: 16,600

    aproctor

    with regard to rebound rates, ignore it. thats what you pay a big brand a premium for. they do the R&D for you.

    if youre really not up on it, why bother with after market?

    just get on the eurocarparts site and get OEM bilstein replacements?
     
  8. aproctor

    PermaBanned

    Joined: 26 Apr 2008

    Posts: 4,078

    Location: Lincolnshire

    If you use matched springs for a set purpose e.g. OEM then yes it is fine, if you go down the aftermarket route, rebound is a basic adjustment variable which is set to the type of driving you will be doing.

    If you ignore rebound rates, you may as well ignore poundage rates on springs.
     
  9. Kingy

    Mobster

    Joined: 18 Oct 2002

    Posts: 3,403

    Location: Leicester

    I'm not looking at aftermarket, (unless I eventually consider an ARB kit) I just wanted to know if the front wishbones need replacing, is it not likely that the reas will need doing too? And if the rear bushes need replacing, wouldn't it be a good idea to replace the fronts? Or doesn't it work like that?

    I just figured that the more stuff that was replaced, the better the ride / handling was likely to be, and I could get it done more quickly, instead of having to take it back in 10k to get the other bit done...

    Is a shock absorber the same thing as a damper?
     
  10. Sin_Chase

    Capodecina

    Joined: 13 Jan 2004

    Posts: 20,580

    Well, it's not like you can "just do the fronts" because the backs are being done. The process will not be any quicker or slower just because the opposite end is being worked on.

    It's still a strip of the relevant suspension components for bushing work.

    If the bushes are on the way out, get them done along with the shocks.

    Wishbones/arms, bushings and shocks are pretty much all synomous with each other.

    Which parts you need to take off and work with and which you do not is entirely dependant on what you are replacing.

    The bushes are still a pretty big job beyond the shock work.