Polyurethane Suspension Bushes. Opinions

TWO

TWO

Zorg Guru (I)
Joined
Dec 5, 2011
Points
94
Location
Chelmsford
Model of Z
Z Sport Roadster 2.2
I've just booked the Zed in for an MOT and service (BMW dealer) :ympray: :-ss and have asked the mechanic to check areas causing severe 'tram lining' (the correct tyre pressures are checked every time the car goes out)

I mentioned I was considering Polyurethane Suspension Bushes and was advised not to fit due to "an extremely hard ride" :-s

As I'm not looking to throw the Zed hard into the bends etc; I just wondered what other forum members opinions are?

One question. Is there a happy compromise........Polyurethane in areas that help to overcome the effects of 'tram lining' and the remainder in rubber................or is it all or nothing?

I'm happy to have OEM rubber replacements, but am looking for the pro's & cons advice.

Cheers
 
IMO if a car passes an MoT done by a competent mechanic,there will not be a lot wrong with the bushes.
In my experience the first thing to look at is tyres.What tyres are you wearing.If they are directional tread pattern,they could be the problem.Tyres such as Falken ZE912,Continental Contact and other asymmetrics are more inline with the tyres fitted when the car was new (Continental and Dunlop I believe)
Mine has poly bushes up front with strut brace and butt strutt and tramlined very badly with Goodyear F1s and Falken 452.It's fine with ZE912s.
There has been plenty written on this issue.
Here's a recent thread,

http://www.zroadster.net/forum/viewtopic.php?t=33550
 
2 comments on this subject...

First is that I haven't suffered tram-lining even on the 18" rims I fitted. In fact it made the ride slightly more stable than the 4 budget tyres on the original 16" rims. I have Falken 452's (directional) on the front, and Michelin Pilot Sports (uni-directional) on the front. In a previous discussion I had decided that I most likely stick with this combination when the fronts needed changing.

Second is that when I needed some front suspension bushes, the independent BMW specialist garage I use advised sticking with OEM. In their words "if they are good enough for BMW, then why change". But then as I had no stability issues, why would I need to use something different...

Personally I feel the issue can be resolved with a decent tyre selection!
 
You seem to have a many tyres on the front and none on the rear. :-s
 
Frank.A said:
You seem to have a many tyres on the front and none on the rear. :-s
Click to expand...
I'm tired. :) Just spent the last couple of hours removing parts from my Zed to sell..

I have 452's on the rear, with Michelin Pilot Sports on the front...
 
I too have suffered from severe tramlining, I have 18 inch rims fitted I still suffer from tramlining now but not as bad. Here is what I have done & the difference it has made.
1. Fitted poly wishbone bushes .... Hardly notice any difference to the standards although it has not made the ride hard & didnt really help tramlining.
2. Fitted strutt brace ... No difference to tramlining at all.
3. New track rod ends & track rods (also known as drumsticks) ... Slight improvement to tramlining.
4. Changed the front tyres to Dunlop SP01's .... Massive improvent to the tramlining, this definately made the biggest difference although I do still suffer some tramlining
I have also found changing the tyre pressures makes a difference, mine seems to run better at around 34psi to 36psi, any lower & it tramlines worse.
 
GazHyde said:
Personally I feel the issue can be resolved with a decent tyre selection!
Click to expand...

At the moment I have fitted on the front, Michelin Pilot Sport 225/45/17 Uni-Directional........same as GazHyde ;) , and on the rear Michelin Primacy HP 245/40/17 Asymetrics. All tyres have at least 3 - 4 mm of tread.

Is this a decent tyre selection?
 
heath said:
I4. Changed the front tyres to Dunlop SP01's .... Massive improvent to the tramlining, this definately made the biggest difference although I do still suffer some tramlining
Click to expand...

Cheers all......it looks like the front tyres are going to have to be reviewed. :-bd

I'm still interested in forum members opinions on the Polyurethane Bushes.

Many thanks
 
I fitted poly bushes on the front wishbones (rear bush) all the other bushes are standard, it helped only a little on the tramlining & you can feel more through the steering plus it feels a bit tighter & it hasn't made the ride hard
 
I fitted poly bushes and it just felt like very pothole was going to pop something through the bonnet, talk about crashy...in fact I thought the bushes made the tramlining worse.
Fitted new struts and springs, none of them lessened the tramlining,
Tramlining wasn't cured either by the 'holy grail strut brace', nor changing tyre pressures,

Got rid of my pirelli p1000 on the front and got rid of the tramlining, Its tyres at the end of the day. especially on the 18" wheels I had on my Z3
 
When Mercedes were designing the face lift SLK they bought in a Z4 to review and pull apart, one of the issues that was raised was that on many European roads, and in particular the UK the Z4 had a tendency to follow every bump in the road and give the effect of tram lining, harder bushes and removing the run flats helped towards the cure, but it was always present. Following investigation they found that the reason for the tram lining was in effect caused by the rear toe in angle changing under deflection thus the rear trying to steer the car. This design is considered very good on the track or for good road holding on smooth roads as it prevents under / over steer, unfortunately on uk roads it make for a hairy ride, this is probably exactly the same thing that is happening on Z3, which is the reason why some people see better effects on changing tyres and bushes than others, it is probably just the roads we drive on.
 
I have fitted Polybushes to both my Zeds. If I'm honest, it did not sort the tramlining issues on the first car but it did make the car feel a bit "sharper".

I fitted them to the "new" car at the same time as changing the front wishbones for MOT last year and it has definately stiffened up the ride. Coupled with the lowered suspension set up handling is fantastic, you feel as though you could throw it into most corners. The downside is that rough roads let you feel every bump and pot holes are to be avoided at all costs.

I guess it's just a matter of preferance. Personally I quite like the firmer ride, but don't expect it to be a miracle cure to tramlining issues. Tyres choice is key.
 
I fitted poly bushes at the front on the '99 2.8. Sorted out the tram lining and made the steering a bit twitchy, which I soon got used to, I did not notice any great change to the ride. I
was going to fit them at the rear as well but spanner man said it was an awkward job to be done when old ones are worn out.
 
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