Poly Bushes vs rubber bushes??

[g57yle]

Hi everybody, im rebuilding my E30 once again,

This time im doing it properly.

1: Does anybody know how good poly bushes are on the rear setup?

2: What Are the pro's and cons?

3: Where can i buy them from?

and any info about them, more road noise?

Also where can i buy bushes for a custom twin diff mount?

Thanks guys

All info is much apprieciated

Gary

[oldroydsr4]

I have powerflex bushes throughout bar rear diff, engine and gearbox (doing them when the turbo conversion is finished). You will only notice a huge diffrene if the old ones are fu%$ed.

However the 325i is used mainly on track and feels lovely and tight. it all adds up to creating a well handling car.

I can't really comment on road noise as i have no interior, but i doubt you will really notice a huge increase in noise.

I got the whole kit from the autosport show last yeaer @ demon tweeks.

I think the total was £200 ish, but this included every thing i.e wishbones, rear beam, anti roll bars etc etc

[DRIFTBOY]

Mine has all poly bushes front and rear, apart from diff which is Z3M, I've noticed no downsides to them at all. It's all good!

[jaistanley]

My 318iS has a full poly bush setup apart from the diff bush which is a ZM part.

The car is very responsive but like it or not there is definitely a lot more road noise (I do have Billy dampers and H&R springs too though). The ride is very responsive (especially with the M3 running gear thats fitted) and 'taught'. I love having the ability to avoid anything in the road without upsetting the car.

I'd definately say that the bushes improve the handling (and braking) but I also beleive they reduce the roadholding ability of the car. I.e. with the bushes you may have less absolute grip in a corner but you can change direction quickly and wothout fuss or wobble). This is much more evident when there is a rough surface around a corner, the suspension cant seem to react fast enough. Aside from lightning the unsprung mass (expensive) I can't see a way around this.

I am having a hard time deciding wheteher or not to fit them to my new project 325i (with S50B32 power and unfortunately, 215/40/17's to accomodate brakes). My last car (a quick 2 litre 16v golf MK2) and the current 318iS have both had poly bushes and in both cases I have loved them; but this time I think I might need the extra grip and the comfort that comes from the rubber bushes from an M3. I say this because i have recently compared my friends 325i E36 (with full E36M3 Evo running gear and poly bushes) to his new E36 M3 GT (3.0 litre). The GT has all standard suspension and bushes and I have to say I REALLY like the way it drives. The 325i is very responsive and communicative but the GT inspires a lot more confidence simply because it can absorb bumps and not all of that (sometimes terrifying!) feedback is there.

Like you I need convincing. Hope my arguments help and dont confuse matters!

What I want are poly bushes with a lower shore hardness (softer poly bushes). Higher than the rubber they'll replace and more 'substantial' in design, but not as hard as many of the poly bushes available. Rally Design may be able to help, I need to see if they do their 'classic' bushes for the E30.

Jai

[Demlotcrew]

hardtailer Said on S14

On the E30 this tendency is counteracted through a fine balance between the stiffnesses of the subframe bushings and the diff bushing. Replacing those with polyurethane ones disturbes this but since the PU is stiffer that the originally used rubber precision of the rear suspension kinematics increases. If Powerflex and the like would know more about what they're doing (especially when considering modern, multi-link suspension systems) they perhaps would design a set of bushes for the rear suspension that is not only stiffer but would also work in the same manner as the original ones, they would be even more effective...

Basicaly this coresponds to what jaistanley has experienced on the road. Hardtailer recommends that the rear trailing arms be stiffened up before going to PU bushes.

Andrew

[ShineOn]

I had a Mk1 Golf I that I gradually uprated for track only use. It had full poly bushes and engine mounts. There is no way I would do that again on a road car - it was horrible. Admittedly it was made worse by a high lift cam creating a very lumpy idle that when sat at traffic lights made you feel sick.

If the car is going to be used mostly on the road, I'd go with new OE stuff. It will still feel great and be a better compromise.