Suspensions

[andytdi]

Hi everybody,

Well its come to that time in my cars life where the shock absorbers and the front arms are compleatly shagged.
I replaced the spirings last with with Eibachs and i was quite happy, i also have a 32mm front Eibach anti role bar.
I suppose my question is, has anybody had any experiance with the front arm kits you can buy off ebay for 140quid? whats the quality like?
Also is it worth going for poly bushes such as power flex?

And lastly i need new shocks, but good ones seem to be quite expensive. i dont really want to loose to much ride comfort (thats why i went for the Eibach springs) is it worth spending 450quid on Eibach shocks to match the springs?

Thanks for replying!

Andy

 

[aragorn]

I fitted one of those 140quid kits last year, and then found myself back under the car 4k later changing them again and replacing both front tyres as they had been completely destroyed on the inner edges due to the arms having so much play in them.

I wouldnt polybush a road car, certainly not the front suspension on the A4, as the entire setup relies on twisting the rubber bushes around, and you just dont know how that will affect the geometry.

We fitted a Meyle kit the second time round, which was £330 delivered from german ebay. Much better and really tightened the car up a treat.

As for shocks, i'd be looking at the bilstein B6 kit. Craig put a set on his S4 along with the eibach springs and is impressed with it. Very smooth ride with no harshness, yet nicely damped thru the twisties. Craig got them through Siena on this forum, and i think they were about £300-350.

I'm not sure on your front ARB. Personally i find the A4 a naturally understeery car, and increasing the stiffness of the front ARB will only serve to increase its understeery tendancies. What i'd be doing is putting the front back to the 24mm Sport item, and looking at fitting a rear one. Remeber that Audi didnt increase the thickness of the ARB on its S4 or RS4 models, although quattro GMBH did offer uprated rear ARBs for these.

 

[aragorn]

Oh and i should say while your under there, i'd look at replacing the rubber bushes in the rear axle, as they will be just as knackered as the front ones, and only cost pennies.

 

[andytdi]

Thanks for the reply,
Yeah people always seem to have different opinions on the ARB, i did have a look for a rear one but i cant seem to find anybody that does it for a FWD a4.
Personly when i put the anti role bar on i found it reduced body role and felt alot more stable through the twistys.
Blisteins look like the way forward, ill have alook around for a price.

Has anybody ever costed up a genuin set of front arms from audi?

 

[andytdi]

Hiya,

Actually i would be interested to here your theory on why a bigger anti role bar would increase understeer?
I was under the impressions if you reduce body role then there will be a more even contact pressure between the 2 front tyres which will result in more grip and less understreer, please correct me though?

 

[jcb]

the main ones were £25 IIRC but not from audi, get all my stuff from Murray Macdonald VAG parts.

I polybushed my tqs front and back. all with the exception of the ARB mounts.
it may rely on bush flex but poly is a considerably more liner flex over time than rubber which starts to degrade from the moment it is under load.

dramatic difference, considerably sharper turn in, no vagueness in steering anymore, much more stable in corners, no harshness to the ride that you get with some cars and ply, that comes from have a multi point suspension system.

consider this though...only £350 ish for a full polyflex kit, but unless you have twice as much time as you think you need, a hyraulic press and lots of elastoplasts....get someone to do it for you!
I took one look at the sheer number of bushes, remembered the ball ache in replacing bushes on my Gti and 9oquattro and ponied up and paid someone else.
cost about £550-600 in labour! worth though as I have been running them for approx 30k and they are just as solid as they were new, I don't envisage changing them before the end of this cars life.

 

[andytdi]

Yeah my mate poly bushed a mk2 golf and he said the differance was huge!

Its a good job i have got access to a 20ton press then!

 

[aragorn]

In simple suspension physics, if you take any car and stiffen the front end, by either installing heavier springs or increasing the ARB strength, you will make the car more likely to understeer.

If you take the same car and stiffen the rear end, you will make it more likely to oversteer.

As the A4 is naturally understeery, due to its transmission and engine layout, and the fact its a FWD, you want to stiffen the rear end up to make it more neutral. Stiffening the front, and leaving the rear stock will make it understeer earlier.

Its related to weight transfer and things, i dont claim to fully understand it myself, but those are the facts in summary. I can probably dig out more info if you wish?

Yes it will feel more level thru the corners, but thats not related to how much grip you have.

One of the annoying things with this suspension layout, is that even if your wanting to polybush it, you still need new arms, because the arms have balljoints built into them, and these balljoints do wear out.

JCB: The ARB mounts are one of the components on the B5 i wouldnt hesitate to polybush, so its interesting that you havent... Was there a reason for this?

 

[jcb]

that will help.
only thing you can't replace on the OEM arms is the ball joint, so short of ball joint failure you are insuring the life of your suspension arms for considerably longer than using OEM rubber

 

[g60leigh]

Mine is polybushed and I have found it a large improvement handling, most of my work runs are on country roads and feel a lot more confident with it now

 

[andytdi]

Its quite an interesting subject, i would love to have the time and money to do some proper reasearch on suspension!
A friend of mine put a G60 engine in a mk1 golf, he put ARB's on to start with but he removed them after a few weeks becasue he didnt like them!
For now I am going to stick with my 32mm ARB mainly becasue its got new polybushes on that came with it. But in the future its really not that much hassle to swap it on an A4, infact it takes about 20mins so i might experiment with the old one!

 

[aragorn]

yup. have a google for ARB and understeer and you'll find many many posts about people on all sorts of cars removing or reducing their front ARB stiffness to help remove understeer and/or increasing the rear bar stiffness to make the car more neutral.

Manufacturers use them so they can use comfortable long travel springs, and not have the car rolling onto its door handles thru corners. When you have stiffened front suspension, ie say coilovers or even stiff springs, i would think theres probably a case for removing the ARB completely, as not only does it cause understeer, it also reduces the independance of the front suspension. I ran my old nova without a front ARB, becuase although it rolled slightly more, it did grip better thru the corners.

 

[jcb]

JCB: The ARB mounts are one of the components on the B5 i wouldnt hesitate to polybush, so its interesting that you havent... Was there a reason for this?

yes, I mentioned this in another thread but can't find it.
ARB poly bushes are a bad idea due to the different angle of force applied to them in comparison to the arms. I clearly have too much time on my hands as I felt the need to illustrate this.

The arm/subframe/ wishbone style bushes tend to have a metal sleeve to protect the bush from a bolt thread or pin. This sleeve exerts angular pressure against the ploy bush material itself and squeezes it using the increased density and resilience of the material to firm up and limit the movement. This reduces the distance between points A and B.

The ARB bush is different as the ARB is clamped into the centre and the forces are rotational.
In the OEM rubber example the rubber has plenty of play in the material between the internal surface and the external surface and it twists as the ARB ends go up and down.
The arrow on the picture is the force applied to the clamped bush.
In the Polybush example there is almost zero rotational flex between inner and outer bush surface. the ARB will very quickly break the clamp tension on the inner surface on the bush and rotate within the bush essentially turning it into a dry bearing surface. As road grime gets into the inner space it acts as a grinding paste and will detroy the ARB.
I bought a car with poly ARB bushes and the ARB itself was 4mm thinner in the bush than its original size.

 

[aragorn]

interesting.

A similar thing ive heard of happening in the vauxhall world with the lower wishbone bushes. As you say the movement is all in the rotational plane and as the polybush cannot be bonded to metal like the rubber can the bush ends up moving around and wearing thru the chassis mounting plates.

This is one of my reasons for the dislike, as its fair to say, if an astra wishbone moves up and down enough to wear thru the chassis, the audi arms must still be moving up and down by the same amount, and unlike the astra, the bushes are also getting twisted in the other plane too. As such, i would never use them. Even for a track car, i'd have to very carefully weigh up the choices, but i'd rather change the rubbers every year, than have to change my subframe because the bush has wrecked it.

 

[andytdi]

My ARB bushes dont look like that picture, they were just strips of rubbery plastic that wrap around the ARM. they came from Eibach so i cant see them being to bad

 

[jcb]

ha, they are worse as they don't fit the ARB properly

The arm bushes on the Audi have nothing like the rotational stress that the ARB ones do and they all have metal sleeves anyway.

 

[aragorn]

Still the twisting will still happen, and if theres enough twisting to wear thru steel chassis plates on an astra, the audi arms are a similar length, and that means theres enough twisting to wear out the bore in the alloy arm, not to mention where the sides of the bushes are rubbing against the subframe...