Front lower arm bushes.

cobraboy

cobraboy

Well-Known Member
I wonder if anyone has thoughts on this ?
I replaced my ageing lower front arm bushes for poly a while ago, in trying to nail down a peculiar problem I have with my wider wheels and lowered suspension.
Basically the NSF wheel turns out when the brakes are applied and the suspension dips, this only happens in extreme circumstances, but nevertheless needs sorting.
The wheel can be seen to move rearward a little in the arch when viewed from the side at the moment of brake application, so I thought that this was the cause and set about making some nylon bushes to better locate the arms.
Now the issue ........
When the arms are bushed with nylon they wont fix together, the ball joint on the strut rod wont fit in the hole in the main arm as they don't line up. It will just go in when the arms are raised, but as soon as the arms are lowered the alignment goes further and further out.
I looked at the other side of the car that is still together with poly bushes and the strut rod bush is clearly stressed and pulled to one side.
So the arms are not designed to move in an arc nicely when together and rely on compliance in the bushes in order to function - not ideal at all when you are trying to hold them from moving around.
This is not due to me lowering the car either as the arms don't go together when held around original ride height.
Unfortunately the poly bushes are even sloppier than OEM rubber when you try to move an arm sideways, they seem only to like working with direct loads along the arm.
It seems to be the only way out is to go back to quality rubber bushes ?
I am looking at the strut rod eye and thinking of heating the arm to angle the eye a little to take the stress out of its bush to start with
Any thoughts chaps ?
 
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I would check the condition of the steering idler for play. Also check ball joints and track rod end ball joint. Lower down the list would be top arm bushes.
 
I have changed the idler for a nice tight replacement and none of the ball joint's have any play. Top arm bushes look to be in fair condition and from what I can make out wont figure in locating the wheel fore and aft.
I have just discovered that if I swing the disconnected swivel back and forth at the bottom it does not affect the steering, so my theory that the wheel turning out was linked to the wheel moving rearward is flawed.
I am beginning to think that as the OSF wheel does not turn out under braking and is held by the much beefier steering box that my trouble is the idler moving on its bracket.
 
cobraboy said:
I am beginning to think that as the OSF wheel does not turn out under braking and is held by the much beefier steering box that my trouble is the idler moving on its bracket.
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If that's the case you should be able to easily see witness marks of the movement.
 
Hmmm
A while ago I did check all the mounting bolts there were tight and didn't notice any fretting. It may be the idler flexing, I just have to figure out in what direction so as to cause the wheel to turn out and then maybe beef up the mounting.
Any volunteers to sit on the engine and watch the idler during a test ?
 
cobraboy said:
Any volunteers to sit on the engine and watch the idler during a test ?
Click to expand...

I've done worse.....

Inner wing would be a lot more comfortable to sit on than the engine, plus as the driver you'd be wanting to look under the open bonnet and over the engine to see where you were going.

I can just imagine what plod would say....
 
Do you think a cushion would help ?
I did do this to find a rattle on my A4, the missus was driving and had an evil glint in her eye as we rattled along a farm track. We haven't seen a copper round here since 1984.
Maybe a go pro camera pointing at the idler would be more sensible, only because I upset her last week and don't know if I want to risk an engine ride at the moment.
 
Somebody is going to have to explain to me how to quote another reply... can't figure that out!
I had the front of my Base Unit strengthened with the extra plates that Classeparts made a few years ago, and fitted their uprated front ARB and purple SuperFlex bushes everywhere in the suspension. I seem to be getting through steering idlers at a rate of about one every year and a half! The bracket has a habit of coming loose and I have to keep a keen eye on it. I would imagine wider wheels would exacerbate the problem, but I'm no suspension guru!
 
mrtask said:
" she won't be able to do you any harm from under the bonnet."
:p:D
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Of course.... I am going to suggest that YOU suggested that.
Trouble is the brakes are quite good, and as a friend pointed out I now have probably three times the contact patch with the road so something has to give, and my money is now on the idler locating bracket.
I haven't looked but how about putting another steering box on the near side and using it as an idler ? They must fit over there as they made a LHD....... .......
 
Rather than the wife, just put some witness marks across everything that could shift. In this case, a thin bead of something brittle like shellac will show a fracture even if the movement isn't a permanent shift.

Yours
Vern
 
Hi Vern
I have the car together with OEM Metalastik on the near side now. The arms went together with no stress on the bushes after I put little set in the strut rod. I have not tested it yet.
I have visually inspected the idler mount and cannot see a problem, it is not favourably located for all round examination.
I still think I am going to have to be looking at it under loading to tell what is going on. Having just had hand surgery it is going to have to wait until I can hang on properly.
I also need to come up with a way to support the bonnet as the rod is only holding one side, braking will twist the hell out of it when open.

Mark
 
Yup true
But the risk of damage to my still soft paint is not worth it, also having grafted an S1 bonnet onto an S2 and got it to fit has taken much fettling and nudglement, can I go through all that alignment agro again ? not if I can help it.
 
Tested today on the local ex WW2 airfield. Checked by standing next to the car and it was still displaying a little turn out of the NSF wheel on a hard stab of the brakes, but much less than with the ploy bushes.
So did indeed do the engine ride :). There was no movement on the idler or the connecting rod across the car under the same sharp brake test.
Decided to try some braking from different speed without holding the steering wheel and car pulled up straight, it is only the savage stab that makes the suspension dip and return that see's a problem.

I will remove the road spring and do a bumpsteer test through the suspension operating range in due course.
So to sum up.... old rubber bushes in lower arms are a partial cause, fitting new poly bushes with wider tyres is a no no as they are not up to the job. Fitting new Metalastik bushes is the best outcome for my situation.

Well it was sunny so I took these.....
IMG_0360 (1).JPG
IMG_0367 (1).JPG
 
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Mark, out of interest what poly bush brand were they?
I have the full Superpro kit for my car ready to fit and have been thinking about your problem and whether to fit mine in the lower arms or not. I've got 245 tyres on the fronts, I think you have 255 tyres all round right?
I'd like to see if we find different outcomes and why if I do indeed fit them..
Jim
 
Hi Jim
245 all round.
I am pretty sure they were superflex.
If you do fit them you will find that you can move the arms sideways without any effort all. I know the arms are triangulated but they seem to need some lateral support as well, the poly is just too soft.
The original bushes have a steel outer sleeve and a steel inner and provide so much more support plus the rubber is harder than the very squidgy poly compound.
I think also the squidgy sides to the poly allow movement there as well.
I bushed the driver side up with Metalastik today and a short drive seems to indicate a further improvement.
Mark
 
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