Eccentric rear beam bushings. Are they useful?

[Stormy_be]

Hello,

Has anyone already used the eccentric rear beam bushings?
I'm talking about the 4 bushings in the rear trailing arms. (PFR5-306G or PFR5-306GBLK from powerflex)

How would these be helpful?

If you put one to the front and the other to the back you could add/remove toe in/out....but does the Zed have a problem with this?
If you put one up and one down, you could change the camber, correct? As the Zed does "suffer" from camber at the back. On the other hand, a bit of camber could give more stability when cornering, correct?

Thanks, Koen

 

[Brian H]

IIRC there is only 1.5 to 2 degrees of adjustment in total with the bushes Koen, if you are going to the trouble of trying to get rid of the rear camber I would suggest you put the weld in kit in. This gives far more adjustment.

 

[Stormy_be]

IIRC there is only 1.5 to 2 degrees of adjustment in total with the bushes Koen, if you are going to the trouble of trying to get rid of the rear camber I would suggest you put the weld in kit in. This gives far more adjustment.

OK, so I shouldn't pay the extra money for these bushes.
But even with the weld-in-kit, would it really benefit the handling of the car?
Or is it more like: the cornering is better with the camber, but if you drive 80% in a straight line, your tires only get worn on the inside?

 

[Brian H]

Drive it like it is for a while Koen, the camber does look excessive but don't worry about it at this point.

 

[Stormy_be]

Hi,

The problem is that I still have the original bushings in...the ones that were put in the car in 1999.
So I was thinking aready before about replacing them all.

At Goodwood last weekend, there was a stand from Powerflex.
They had a board setup with 4 the same front triangles, but with 4 different bushes. So that people could feel the difference in play between: standard (new), yellow, purple and black powerflex bushings.
The difference was really HUGE.....and that was compared to NEW standard bushings, mine are 16 years old...

So I was going to order powerflex black.
As there is the choice between centric and eccentric, I was wandering what to get ...they have the 2 types for the front and the back.
At the front I would certainly take the eccentric as I would need the added camber at the front for cornering in my slalom events.
I don't know if I would benefit from it at the back or not.

Regards, Koen

 

[Brian H]

You will get about 2 degrees camber adjustment at the front from the BC suspension Koen, I agree with you about replacing the rears bushes but I would stick with centric. I opted for the purple centric bushes for the trailing arms but have black bushes in the rear beam. It is quite right back there now.

 

[Stormy_be]

Thanks Brian.

So I will go for eccentric at the front and centric at the rear, black all round.
Order placed.

Regards, Koen

 

[lmrdave]

Front eccentric is good for setting caster (which is nice), camber can be introduced with washers added the strut mount bottom two mountings (from memory).

 

[Stormy_be]

Hello Dave (?),
Your post got me thinking about the front triangles and the changes the eccentric bush make to the setup.

Please anybody, correct if i am wrong.

The eccentric bush at the front will move the back of the triangle left-right. This makes the bottom of the wheel hub move backward or forwards. As said, changing the caster.
What would be needed to change camber?
You won't be able to change the camber with the bottom triangle (except changing the complete triangle, as Tommy did on his drift zed.
Still correct?

So you would need to change something to the shock/coilover attachment points.
The most common is on the shock top mount, but it has its limitations.
The top mounting shock to hub is not a real option as you won't be able to move it a lot (you will be hitting the hub quickly).
As suggested, the lower fixing of the shock.....would that be a good option.....maybe... anybody else? Thoughts?

Thanks, Koen

 

[Dino D]

With the BC kit I was only able to get -1 degree camber via the adjustable top mounts it comes with (although more should be possible but it seems to vary from car to car).
I believe in the US a common mod is to use Z3M top mounts or 'hats' as they say and they also invert them.
I'm not too clued up just recall reading it on BF.com.

Eventually it seems the guys end up with the full M front suspension as they replace parts.

 

[lmrdave]

The front eccentric bush might alter camber (but not much) and not independently of caster. Adjustable top hats are good if you want to alter set up and play around to see what is best. I have just added a washer to each of the lower mounting bolts on the strut, giving me a touch of negative camber as I'm only using the Z3 to go to work in!

Not used eccentric bushes on the rear of the Z3, but have used similar on similar IRS / trailing arm setups on other cars, generally for alignment, there doesn't seem to be quite enough to correct the negative camber once the rear is lowered.

I shall try to remember to measure the camber on the front if I can get it in the workshop.

For fine tuning the handling I think the car screams out for thicker anti roll bars. There is an after market set that increases front and back by 3mm, but as the rear is smaller than the front to start with this should tighten up the rear more and in my mind bring the balance of the car to a more neutral or slightly rear/oversteer bias, rather the stock understeer bias. This is only theory, I might try it out but I'm not sure whether to stick with the Z3 or try something else.

On a side note I love Ieper, spent more than a few holidays over there spannering for classic rally cars, good times!