Bushes Which Part Numbers

[Alex Funnell]

Hi Guys,

I will soon be replacing all of the bushes on the rear end and the front wishbone bushes as there is alot of sag. Speaking to vehicle dynamics at work they steered me away from poly bushes as I will loose refinement in the steering and handling and make the car instantly responsive. It will also increase the loads in to the sub frame and reduce the life of the components. Finally you will also fins yourself chasing the slop in the suspension around the car until you have a completely new chassis. This leads me down the route of stiffer bushes. Has anyone had any experience with fitting different bushes from the m3 or z3m? Are there any difference in size? which provides the best stiffness?

 

[Wookee]

Hmm... you want stiffer bushes but not polybushes? There may be some truth in what you have been told when talking about the front end, but not the back I wouldn't have thought.

Suspension set-up is an almost personal thing, what suits one may not suit another. I'm a biker and ride almost everyday and I've had a few bikes, being a big bloke I've had to play a bit with the suspension settings on all of them and have stuck to the adage of changing one bit at a time.

This is the approach I took with my Z3 (85k on the clock 1.9) which had a very, very twitchy rear end when I got it. I have a stretch of quiet road near me that is a 50 with a roundabout at either end and some of the road surface isn't great. I used this as my test track to find out what improvements worked.

The first thing I did was change the rear top mounts result was no difference.
Then I changed the rear shocks and there was a slight improvement.
I had already purchased new drop links for my knackered ones but I had to source some ARB poly bushes and then I fitted them altogether. **** me what a difference! The car now grips at the rear end like brown stuff on a blanket.

I can now feel that my front end is a bit 'worn', but it's predictable and pretty good fun so I'll leave it for a while.

Incidentally the very first thing I had done when I bought mine was to replace the front tyres and have the alignment checked. The rear camber and toe are out and can't be adjusted with the only way being to change the wishbone bushes, but like I said it really grips now without that change so I'll leave them be for now.

 

[Alex Funnell]

I am buying bc racing coil overs also

 

[GazHyde]

Poly bushes always causes the same discussion. I can say with certainty after rebuilding the rear sub frame on mine that even with *coughs* "quick road driving" I don't need poly bushes. Went standard OEM quality rubber for everything apart from the diff bush (it's just much easier to fit). Sticks to the road like glue now!

 

[Alex Funnell]

Are the Z3M bushes at the front stiffer? Same for the rear? Or E30 M3?
Do they fit?

 

[Dino D]

And I can tell you with certainty that a z3 with all poly bushes and BC coilovers (with proper set up) is better than any standard car I've driven. It's reminds me more of Hondas and VW's than a wayward BMW of the past - dare I say as good as a TT ( I liked the stability of a TT over the Z3

It's a very personal thing. Your vehicle dynamics colleague have good points but I think you have to look at things in context of what you want/do with your own car and not just high level broad strokes opinion about vehicle dynamics in general.

Longevity of other components-If you planning on doing another 100k - 200k miles with the car then maybe longevity is an issue otherwise is it really? Which components exactly and will those components not need renewal at some point anyway due to age?

Chasing around slop in other areas- you will do this in any case (and should) as it is unlikely the rest of the bushes are all ok at this age.

More directness/loss of refinement- I wanted that, a standard Z is not as direct as I'd like I don't think you can get these cars to the point of being overly direct - they are no Lotus Elise. Others may prefer more numb steering.
The amount of camber dialed in made a difference here (you can get the BC with camber adjustable top mounts). Just 1degree on mine was noticeable and feels great.

I don't disagree with what you have been told but have found in context of what I wanted from the car you have to decide based on how you use it and where you drive it.

One thing I will say is rear subframe bushes - for me a no brainier to be stiff.

It's a lot of fun and very rewarding but whichever bushes you use I don't think you'll feel shortchanged as fresh suspenion just makes such a difference compared to what you will be driving on now.
Remember to have it set up (corner weighted) and camber adjusted properly on the front-that alone is probably more beneficial than the difference between new rubber/poly bushes.

As to your question in Z3M bushes - I believe many of the bushes are stiffer than non M products (I know the diff bush is) but I'm not sure which exactly. I understand that not all suspenion components from the front can work without changing all the suspenion to match either as the M has different components - the front wheels sit more forward.
There will likely also be an M tax on M parts and don't forget M owners also uprate their bushes.


Which spring rates are you going for by the way?

 

[pgunter]

@Alex Funnell REALOEM.COM is your friend here.. Put in the last 7 digits of your vin and you will find a wealth of part numbers in the different areas of the site.

Good luck and I would agree with @GazHyde, the standard OEM are more than enough for all but heavy track use.

 

[Low Rider]

Poly bushes always causes the same discussion. I can say with certainty after rebuilding the rear sub frame on mine that even with *coughs* "quick road driving" I don't need poly bushes. Went standard OEM quality rubber for everything apart from the diff bush (it's just much easier to fit). Sticks to the road like glue now!

Gaz. It sure does thankfully I'm sure I would get used to it if I was your passenger more often

 

[GazHyde]

I will point out that I'm not inherently against poly bushes. I personally think one of the big misconceptions is when people replace worn (and in some failed) rubber bushes with poly and then immediately assume that means that the rubber isn't adequate.

It's actually the worn out rubber which is the cause, and replacing it with fresh rubber bushes will give almost (and I iterate almost) the same initial effect. I take my own car in point as to how well the Z3 handles on fresh rubber.

If however you want to improve on the standard rubber then take that as a separate considered step - you are now upgrading. If you want to drive your car hard or track it then I would of agree poly is a good idea. For daily driving use, save your money and put it in the petrol tank

I think @Dino D puts it best with this

whichever bushes you use I don't think you'll feel shortchanged as fresh suspenion just makes such a difference compared to what you will be driving on now.

 

[Alex Funnell]

Which spring rates are you going for by the way?

Went with the 58.8N/mm (6kgf/mm) as I will be driving on the road.

The bushes are compatible between the cars correct? Don't want to order the m3 or z3m bushes to find they have a different OD or length

 

[Dino D]

I also went for 6kg all around but ended up then swapping the rears for 8kg as the 6kg bottomed out - this is on the road, normal driving but on some bad bits.
I know @Mnbrennan runs 6kg all around on his coupe with no issue though.

Re the Z3M / M3 bushes - I can't say for certain, best to check real OEM and also the dealer before you order- Sopers of Lincoln are helpful and give a forum discount.
The Turner Motorpsort (US) site is useful with part number etc and should help as they show compatability too:
https://www.turnermotorsport.com/BMW-Z3/c-91-bmw-suspension-bushings-and-mounts

 

[Alex Funnell]

Thanks for the help.

@GazHyde Do you recommend replacing fixings when doing the rear bush refurb?

 

[GazHyde]

Not sure what fixings you mean? We haven't needed to replace too many nuts/bolts except on the rustiest cars.

 

[Nodzed]

Alex, just to chuck my two penny worth in (no pun intended!!) Mine handled badly when I first got it so improvements were drastically needed, I went stock front and back with shocks, bushes and ball joints (and rear springs) from BMW with the exception of the front wishbone lower rear bushes where I used Powerflex poly bushes, not sure why other than I had read the stock ones were a possible cause of tramlining?? Anyway the stock parts along with a fresh set of tyres transformed my 2.8, its more than adequate for my normal use, even spirited driving. I haven't got an opinion about track day set up as I haven't done one (yet) so cant say how the Zed in stock for would cope but there's plenty of people on here that have and could.. Good luck though with your decision and would be interested to know the results.

 

[Wilko58]

Alex, just to chuck my two penny worth in (no pun intended!!) Mine handled badly when I first got it so improvements were drastically needed, I went stock front and back with shocks, bushes and ball joints (and rear springs) from BMW with the exception of the front wishbone lower rear bushes where I used Powerflex poly bushes, not sure why other than I had read the stock ones were a possible cause of tramlining?? Anyway the stock parts along with a fresh set of tyres transformed my 2.8, its more than adequate for my normal use, even spirited driving. I haven't got an opinion about track day set up as I haven't done one (yet) so cant say how the Zed in stock for would cope but there's plenty of people on here that have and could.. Good luck though with your decision and would be interested to know the results.

How did you find the prices for stock bushes compared with the polyurethane ones @Nodzed ?

 

[Nodzed]

I think the Powerflex were 45 Just bought some for the M so I can check for you never bought stock so can't really help with prices but the powerflex are well worth it plus you don't have to get then pressed in whereas stock ones will need to be pressed in.

 

[Wilko58]

I think the Powerflex were 45 Just bought some for the M so I can check for you never bought stock so can't really help with prices but the powerflex are well worth it plus you don't have to get then pressed in whereas stock ones will need to be pressed in.

Sorry I was wondering if you had priced up the Powerflex before deciding to go completely stock except for the front wishbone lower rear bushes (which I'm going to do Poweflex (or 'M') as well because of the stock being rubbish!). If the price difference is drastic I could well go with stock although as you say, in most cases the Powerflex are easier to put in.

 

[Nodzed]

No sorry I just didn't know any better back then that was two Years ago, the M is going totally powerflex all the RRPs are on the powerflex site along with distributors all mine came via Euro car parts

 

[Nodzed]

@Wilko58 just to be clear when I did the 2.8 I didn't just go OEM quality I got everything from BMW I really wouldn't recommend that, it was expensive. Powerflex option is cheaper than BMW, however as has been said above OEM quality after market are fine and will greatly improve the suspension, but some of the poly bushes are just easier to fit as in diff and wishbone rear bushes where the OEM (quality ) ones need to be pressed in. (sorry for the rushed responses earlier I was using my phone to access the site)