Polybushes

[James_M]

Hello All

Spot of advice needed please.

I have a 135,000 968 Sport that I've had for about 5 years. I've read / been told many times that renewing the shocks and replacing the bushes with Polybushes is a good investment. The Porsche specialist I use (and like) doesn't think this is necesaary, though there is some play in one of the front struts. However, part of the reason I like him is he doesn't spend money unnnecessarily and I'm wondering whether the work might be worthwhile anyway despite not being strictly necessary. As far as I can tell the supsension is all original.

The problem is that while shocks are self explanatory, what exactly is a bush? How many are there on the car? Are they all the same? Why is a Polybush different?

While I'm here I guess I should ask about which make of shock to go for too. The car does about 6000 miles a year and maybe three trackdays per year.

How much should I be allowing for this work?

Having said all the above, this may be all a pipe dream becasue I think a new clutch is also on the horizon (also original I think). How much for one of those?

Thanks a million

James

 

[Paul RN]

I'm sure someone with more knowledge will come along shortly to fill you in. In the meantime heres a wiki article on bushes

http://en.wikipedia.org/wiki/Bushing_(isolator)

I think one of the dis-advantages is the firmer ride, although the wiki doesn't really bring that out. In fact it suggests they can be made the same as the original rubber bushes which doesn't sound like what I've heard in experience.

£650 was the ball park when I asked for a 'rough' price on a new clutch and fitting from a 968 specialist a month ago. I don't know how good or bad that is, or what clutch in fairness. Be interesting to hear what others say.

Lastly, upgrade what you what as your specialist is just trying to be helpful but ultimately its your car and its quite just nice to upgrade a few things even if they are not needed. You can then re-sell the old parts anyway, cuts down on the cost of new.

 

[Neil Haughey]

Short answer: Unless you have clearly worn bushes its not worth poly bushing.

Longer answer: Ask those who gas on about poly bushes what exactly they have used their 944/968 for? The reason why I say this is that none of the race cars I know of have been poly bushed because its not allowed under the PCGB club championship rules. Does this make the car into a unweildy nightmare? No in fact quite the opposite, once you have driven a car on springs 3 or 4 times stiffer than stock on tyres similarly stiffer than stock but on stock bushes you realise this nonsense about poly bushing our cars is just that, nonsense (rose joint/solid bushing maybe but that is really extreme and expensive). If your original bushes are shot then of course they will require replacing then you have this decision to make otherwise its a waste of time and money just as your indie advised. Anyways if one was to poly bush the only large pliable bushings attach the rear spring plates to the torsion bar and tube, the others will make next to no difference. However the problem with that bushing is that the suspension design requires a little compliance at that location such that the rear suspension can move up and down freely.

 

[kenwill]

Hi

I did poly bush the front end of my car but it broke up after 4 track days last year and I went back to the Porsche rubber ones. If you have poly bushes you have to lube them often if your going on track as they are grippy and will break.

I think that the poly bushes are supplied in 2 parts for some applications and that makes it easier to fit.

Your annual MOT would probably pick up any worn bushing although there are quite a few on the 968 and may get missed.

If your struts have the movement you describe it will probably be affecting the handling to some degree. What about the top mounts are they split or worn ?

But if you have managed to date with stock then refreshing with the same or upgrade to the Koni adjustable would probably be all you need. And at the mileage you have indicated I suspect the general concensus would be that the shocks are probably past there best and getting a bit lazy.

You can obviously change to KW or GAZ but the cost is a lot more.

 

[James_M]

Thanks for the advice chaps.

As it turns out I have had to replace the clutch so suspension issues are now on the back burner. Sounds like there is no point in replacing the bushes at all unless they are badly worn, at least for my purposes.

I did get prices to replace the shocks but the issue that killed the idea off for the time being is the front top mounts. Another £500 +VAT for the parts and you won't know if you need them until after the front shocks are off...

Cheers

James

 

[frogisland]

...and of course it depends on the shore rating of the given poly bush. Delrin is another option. Probably can't beat using standard Porsche bushing, certainly good enough for the race cars and will offer composure and longetivity on the road.

Re bushing:

Front-
caster mount
top mount
front of wishbone to cross member
arb, wishbone and bracket
engine mounts

Rear-
torsion tube to body
spring plate to torsion tube
trailing arm to torsion tube
'banana' arm of torsion tube to body, upper and intermediate bushing
arb, drop links and torsion tube
gearbox to rear upper cross member

Plenty to think about, replacing worn bushing does 'tighten' the car up, otherwise would check rear dampers - noted mine had deteriorated by 70k miles

Have replaced all of my bushing with monoball, rose joint, solid alloy etc......fantastic on track, great feedback etc....need to keep your wits about you on poor A roads though.

JP