VL Bump Steer Problem

[Azzag]

Hi,

First time I've ever asked a question on a forum so try to bare with me lol.

I've got a VL commodore, 6 cyl auto which I've had for about 5 years or so now with only 118000 legit on the clock. I previously had 2 VL's before this and have never seen a VL with this bad bump steer. When I got the car it was completely stock, with absolutely nothing done to it and in MINT condition. The car had a slight tracking problem but thought nothing of it. As time went on I eventually saved enough to get the car lowered, new bushes, new lower and upper control arms etc on the back from Pedders. After this the bump steer was really noticeable. I changed everything bit by bit and the problem seemed to be getting even worse as time went on. I took the car to several suspension places to get it checked and it always got passed off as nothing at all wrong with it. I started to get things changed bit by bit. I changed the steering rack twice, the steering column, wheel bearings about 3 times in the last 2 years, rotors have been changed twice, tie rod ends at least twice now. I then bought new King Springs and Monroe dampers but with original height for front and rear about a year ago and now the bump steer is SEVERE, sometimes nearly taking the car off of the road, especially if turning a corner and the car hits a small bump in the road. I've had at least 6 wheel alignments, after every time of changing something and have tried VY SS 17" rims on the car with 235's, I've had 16" Walkies on the car, the original 14" stock rims on the car and currently 15" cop rims with 215's and have found no way of fixing the problem. I've also noticed If I'm driving down a road and drive along parallel dips in the road the car will follow these taking a fair amount of effort to steer out of these "ruts". I've occasionally nearly been taken into the other lane if these ruts run over the white line!

I dread driving the car over 80 now and only use it only for work now (funnily enough I work at Holden, Elizabeth). I'm really starting to loose faith in the old girl because I just cant seem to find a solution to fixing this problem. I'm quite happy leaving the suspension stock if the problem was fixed. Other than this the car has never had a problem and is very reliable. The car's also in good condition for its age. I'm far from being an expert when it comes to suspension and would appreciate any help with this problem,

Cheers. (Sorry about the long life story)

[88GreenVN]

Bump steer is normally caster issue. You may have too much 1 way or the other. I had this in my VN when fitting new springs to the front of my car. It was too high in the front (country pac V8 units) so I put an extra sring rummer in the back to level the car up. It was all over the road on every bump. Too much caster so pulled the extra rubber out and the issue stopped.

See if you can find out what caster you have.

[Reaper]

Bump steer is normally caster issue. You may have too much 1 way or the other. I had this in my VN when fitting new springs to the front of my car. It was too high in the front (country pac V8 units) so I put an extra sring rummer in the back to level the car up. It was all over the road on every bump. Too much caster so pulled the extra rubber out and the issue stopped.

See if you can find out what caster you have.

Can also be a geometry issue where the front tie rods are no longer in plane with the rack, usually caused by excessive lowering and/or bent/worn suspension components. Was a common problem when people fitted HQ style stub axles to the front of LH/X Torana's back in the day before the CRS drop axle stubs were available. In general more Caster is great for high speed stability but the sacrifice is the turn in for corners. Less caster will make the car feel nervous and jittery mid corner.

Reaper

[detox_nath83]

Ball joints worn????

[jatsvl]

bent stub axles?

[VK_3800]

What do the wheel alignment specs tell you? The whole car could be bent, who knows - you really need some accurate and specific measurements to find out.

[Not_An_Abba_Fan]

The first thing that popped into my head was worn Panhard rod bushes, the bar that connects the body to the diff. If you can push the back of the car and it rocks sideways while stationary, then the bushes are worn.

The other problem is as Reaper mentioned regarding the rack. If the rack isn't centralized and the length between the inner and outer tie rods aren't exact, it will produce the effect that you are experiencing.

It may also be a bent lower control arm.

[Azzag]

Cheers to all who replied. Appreciate your input. Im' thinking of getting standard springs put back in the front and rear. I had a real close inspection at the ball joints and did notice the front left looks "dodgy". I never noticed this before and now when the wheel is on with lock nuts done up and jacked up the entire wheel and rotor wobble with what looks like movement in the ball joint, of which the other side doesn't do.

I tried pushing the rear of the car sideways while stationary to see if it rocks and it is as solid as a rock. I've still got the Pedders adjustable panhard rod in there with Nolathane bushes, but looks ok.

I'll try to keep this brief but heres some final measurements from my last steering alignment not long ago. Rear: Camber Left -0°08' Right -0°38' Individual Toe Left -3.1mm Right +4.3mm Total Toe +1.2mm Front: Castor 10° Left +2°03' Right +1°41' Camber Left -0°47' Right -1°21' Individual Toe Left +0.7mm Right +1.1mm Total Toe +1.8mm Setback -11.0mm

With the steering rack not being centralized, could this happen by an error in changing over the rack or something damaged like the x-member brackets etc?

I also noticed after changing from Pedders springs to King springs that the car now sits slightly higher on the front and lower on the back in regards to being level. I cant remember the exact King springs I got put in but they were suppose to be standard ride height ones. I was also looking for a "softer" King spring but the ones I have on the front are super rock hard. I reckon they feel more harder than the Pedders I had in there before. I'm not sure if having hard springs in the front could cause bump steer or not? The back end feels ok though.

Cheers again

[VK_3800]

Aside from the fact that the diff seems to be pointing to one side a touch, those specs look OK enough not to be causing the issue. The wheel alignment specs should also have things like the track and wheelbase, and how they compare front to rear and side to side - this is good info on whether the car is still straight and square.

Not sure what you mean about the steering rack not being centralised - the toe measurements will be taken from wherever the wheel aligner chooses to point the steering wheel.

Definitely fix that ball joint and any other mechanical issues before going any further, you should have been refused the last wheel alignment with this issue as its pointless when the suspension doesn't maintain its geometry. If its as bad as you say this may explain why it got worse with the new springs, the damage could have been worsened when fitting them. Are all of the front end bushes definitely OK? They can get very soft and damaged before obvious problems appear visually.

[Azzag]

I'm not sure either about the steering rack not being centralised. It was a comment from "Not_An_Abba_Fan".

There were no other specs printed out when I got that wheel alignment unfortunately. The cars definitely never been in an accident, I know the first owner of the car.

Bushes on the front end look real good. They were replaced around 2 years ago, but still look in very good condition. I'll get them checked out anyway though soon.

I agree, the ball joint could cause all these problems, but the front left wheel never used to wobble like this now and I've always had this bump steer problem. Could of been a sign of the ball joint gradually stuffing up? I'll get this ball joint looked at and replaced in the next few weeks, get another wheel alignment and let you'se know how it all goes.

[Not_An_Abba_Fan]

Centralizing the rack puts equal pressure on each side and makes the car track straight if there are no other issues. Count the turns on the steering wheel from lock to lock and divide by two. Set the wheel at that position and see where the front wheels are pointing. If they are not straight your rack is off centre.

[Darren_L]

I'm assuming you are referring more to rear bump steer ?
if so, I had the exact same problem with the VH. Hit a bump while cornering on the highway and I almost had to opposite lock the thing to keep it in a straight line. It was quite savage. I don't know what the car was like before I lowered it and replaced all the bushes etc, because I just bought the thing with completely shagged factory suspension, drove it home and put it on stands before carrying out the resto.

But it was only after getting it on the road and driving it for a while that I noticed the terrible rear bump steer. I tried everything from different tyre pressures, backing off the rear koni's, I was even considering going back to rubber voided bushes on the rear control arms, and/or getting a watts link system fabricated up. I was fully aware of the practice of fitting adjustable panhard rods when lowering a Commodore, but I had carried out rear axle alignment measurements and there was very little difference between left & right, so I didn't bother fitting one. But eventually, out of desperation I fit an adjustable panhard rod and set the rear axle alignment up with a tape measure. The difference was nothing short of amazing. It was a totally different car to drive...

You said you had a pedders panhard rod ? Is it an adjustable one ? If not, I'd fit one and spend your time setting it up correctly. Might just be the answer to your problems.
It transformed the handling of my car.

[VK_3800]

Not_An_Abba_Fan that makes sense but wouldn't you have to disconnect the rack from the steering arms temporarily to check that without the steering stops interfering?

Darren_L since there is no steering in the rear its not really bump steer, but an interesting issue. Again proper wheel alignment specs would show up issues like offset rear track which seems to be what you are describing, I'm curious as to how far out was yours before fixing it?

[Not_An_Abba_Fan]

No, the steering will hit the stops when the tie rod ends are connected regardless. What you are doing is checking that the rack has the same number of turns from centre to each stop. If it doesn't then the rack will be off centre and the toe out on turns will be incorrect as well. Every time you hit a bump, the steering moves a bit anyway but if the rack is not centred the toe out on each wheel will be more than it should be once the steering is turned a bit. This will tend to want to pull the car to the side that the wheels move when a bump is hit.

[vr1uz-fe]

i am a suspension mechanic have you had the ball joints changed it sounds like the ball joints are rooted and all the loosers that checked dont know how to check commie lowers right either that or your cross member is loose or the inherint prob of the vl is causing crab walk if so the you need you chassis welded up

[Azzag]

Yeah the panhard rod is adjustable. Apparently this was adjusted when I got the wheel alignment too.

I really believe so many of these places that supposedly check suspension (wont mention any names) dont know what they are looking at half the time or just dont look. They would of made more money from it in the long run though, because If i had known earlier that it may of been damaged then I would of paid to get it repaired if it was the suspect issue causing this problem.

I totally understand what you mean now with the steering rack not being centralised. I think I'll look at that this weekend before I do anything else. I'll also take a look at the x-member and see if its solid and all bolts are still tight etc.

I have noticed though when I hit a bump it doesnt really move the steering wheel to much (a little), but the car really moves in the direction/ side the bump is on. Its basically the car steers itself (to a degree) according to bumps in the road and steering the car controls the overall direction of the car, thats how bad it is!

[vr1uz-fe]

it is not the rack i have lowerd many comodores and own a vr that has the same crossmember with the same rack specs

i am leaning to the inherint prob with vk and vls where when they have too many km's on them the chassis can break it was abig deal when the taxi vl's were let go then when hit at 60 the whole car would split in half so you have to get them seam welded down the chassis

it might of been in a crash and not mended right and the loosers that checked your car are just knobs and i work at an un named suspension shop