suspension issues with a BFIII wagon.

[Bushbasher]

This is about tyre wear and looking for the cheapest fix I can live with...

Apart from the vehicle issue my missus is also adamant that she doesn't want me to touch "her" car because she likes it the way it is even though I tried to explain that the car is unbalanced and potentially dangerous in an emergency situation as well as the tyre issue.

Ok, so my missus' wagon was set up, by the previous owner, to tow a heavy caravan so he was talked into having the rear springs reset and an extra leaf added. It's now nose bleed high at the rear. To help compensate, they fitted stiffer Pedders front springs so that's quite high as well, not that I mind because the wagon goes up dirt roads alot and into the occasional paddock etc.

The problem is, the rear is still stiffer than the front causing the car to feel like the front is wandering on bumpy roads plus the rear eats the shoulders off the tyres because it doesn't lean over as much as the front in corners. Rotating them just means the front finishes the job with still 10-15k km worth of tread left in the middle of the tyre. If I don't rotate I'm changing rears at nearly twice the rate of the front because they take the shoulder down to canvas by just over half way through the tread life.

I've looked at removing the extra leaf from the rear spring pack but it's not a job I can do in the driveway so I'd have to pay to get it done, but I don't want to go to even stiffer front springs either. So now I'm wondering weather I can get away with a stiffer front sway bar to help balance the body roll thus reduce or eliminate the rear tyre issue.

So my question, well questions, are:
Will this have the effect I'm looking for without losing too much compliance on uneven surfaces and eliminate the wandering AND fix the tyre problem, and if so, what is the stock sway bar size and is an XR6 or XR8 sway bar thicker or do I need to look at aftermarket?
; because it seems to me, If I have to pay $3-400 for a sway bar I might as well pay someone to remove the extra rear leaf. This is also a problem because unless I can have the job done and finished in the driveway while the boss is at work, she'll veto the change and make me put it back the way it was. Any opinions or guidance on my dilemma would be much appreciated.


Cheers
Bushbasher

[BENT_8]

Just grab a set of standard springs from a wreck and swap them over, do the bushes while your at it, probably set you back less than a couple of hundred dollars all up.

[Raptor]

Bushbasher, I've understood what you've said but I am having trouble with your explanations. So instead of answering your questions can I ask a few of my own. They'll be a few comments thrown in as well

..causing the car to feel like the front is wandering on bumpy roads..

Good chance what are feeling is rear steer due to the raised rear suspension height with the live axle/re-arched leaf springs. To minimise this effect the factory places the front of the rear spring near horizontal to the road. On XR wagons/utes it's even positioned slightly lower at the front for higher speed stability - your's will be the opposite of this. That's bad.

...plus the rear eats the shoulders off the tyres...

That sounds more like under inflation to me. What are the pressures set at? Are they different to the fronts?
With a live rear axle the tyre tread should be staying pretty sqaure with the road at all times.

...because it (the rear) doesn't lean over as much as the front in corners...

I'm pretty sure Falcon wagon bodies are stiff enough to ensure that the front and rear lean over the same amount in corners. Different suspension set-ups (IFS vs live rear) will mean the tyres do different things though.


Also, how are the shock absorbers?


It'll blow the budget but best fix (whilst retaining the higher ride height apparently preferred by SWMBO) would be to fit RTV suspension front and back. Largely due to the 1-tonne load capacity and the addition of rear track bars the rear suspension of these is also much stiffer than the deliberately soft front - yet they wear out front tyre first in my experience. Though that may be due to lower load rating/softer compound vs the rear in the sizes I run.



.

[Bushbasher]

Hi Raptor, shocks are good and tyre pressures are ok too. Tread wear is even across the face of the tyre but because the rear is stiffer than the front the nose dips into the corner but the stiff rear wont let the body roll at the rear so the tyre side wall is having to compensate thus scrubbing away at the shoulder. Unlike the steer tyre though, it's only taking the very edge of the shoulder, maybe less than 10mm; just the tread that rolls around to the side wall, where the steers take rubber evenly from the side tread all the way to the face of the tyre, if that makes sense.
Ride height front to rear is maybe 2" difference, 3 at most, not unlike our old AU wagon when it was unloaded with no weight in it. The difference with this thing is, you load up the rear and the blooody thing is still 2 inches higher than the front... but does lean a bit better with the weight and feels more stable.

[Raptor]

Thanks for your reply.

In response to your initial questions:

Yes a stiffer front bar will limit how much body roll occurs and transfer more of the cornering load to the front tyres. Reducing the bodyroll should also reduce the wandering, especially if its occuring as I suspect from the rear live axle steering the car as the suspension cycles. But this will come at the cost of some loss in compliance on uneven surfaces.

Sorry, can't help with sizing.

[snap0964]

Probably, first thing you need to do is get your Mrs on side, then the rest will flow easier - the best thing to show her that she'll understand is the $$$ in replacing tyres - show her a tyre with that bad wear to the belts. To somebody not technically minded, you could be there for ever explaining suspension.

The rear springs don't add up - simplest thing out of the pack the prev owner could've done is fit one tonne rear springs - a few on here have done that to their wagons with no problem. My factory EF XR6 wagon springs are reset 5 leaf instead of the std 4 leaf and it sits 1.5 " lower than my std EL Wagon. So reset springs my a*se I'd suspect.

So your options are like the other guys have said - return it to std suspension, I'd add, do your front shocks while it's apart - surely someone on the forum has some cheap std springs to sell.
Otherwise maintain what you have, but read through the couple of RTV conversion threads on here to get an idea what properly needs to be done.

It is normal to have some scrubbing on the rear outsides, not to your extent though, of course. So long you don't have that type of wear on the insides - that means of course the prev owner was carrying too much weight and the axle tubes have bent - and it would've been a LOT of weight.

[Bushbasher]

These springs are 5 leaf and were re-hardened I believe. The last owner was an older guy with no mechanical knowledge but lots of money I think. I have over $8k in receipts for work done and that doesn't include the complete suspension rebuild front and rear including all new bushes and links along with the new springs. It had the trans rebuilt, LPG installed, aftermarket install 2600kg Hayman Reece tow bar, new coils and plugs twice which turned out to be the LPG ECU, which was replaced, I have the coils and plugs as well, 2 spare new front hubs, new discs and pads all round, big ARB bull bar, decent head unit WITH the adapter wiring harness so the steering wheel buttons work... the list goes on. This was a money no object just fix it kind of guy. If he says the rear springs were done then they were done.

[snap0964]

Well lets hope the $$$ extended to replacing the little cooler near the bellhousing to an external one.

[Bushbasher]

You bet, it's a big a$$ trans cooler behind the grill.

[Crazy Dazz]

Further to what Raptor has said, I too am not following.

I had a couple of wagons, and yes driving on gravel roads was an adventure. The rear effectively "skips" across the bumps, and it becomes directionally unstable. And yes, it would be worse in yours with the tougher springs.

I'll be honest, I cannot fathom how this is ripping your rear tyres.
Yes, stiffer springs means more impact is absorbed by the tyres, but that shouldn't result in what you are describing.

The bad news is that with that HD suspension and LPG, I honestly do suspect that your tyre are under-inflated.
The only other thing I can think of, is that somehow this rebuilt suspension is out of true and the car is crabbing?
(And I'm assuming that your bearings and axles are ok?)

Stiffening up the front is not IMHO a good idea given your situation. It may make the car better balanced to match the back and the front, but over rough roads it will make it worse.
As others have said, I can only suggest returning the rear closer to stock, and fitting good shocks all round.
I'll be honest, I have never stripped down a leaf rear. But I've done coils and found it easier than many suggest.
If you hunt around, and you're prepared to ull them off yourself, you can probably find somebody parting out a wreck for cheap. Not sure which models were the same, but can't imagine there was much difference in the leaves.

[Bushbasher]

I had a dual fuel AU wagon for 8 yrs and 300k km and it never did this due to tyre pressures. In fact, I've had 5 other dual fuel sedans in that time as well including my current Sportsman and none of them ever scrubbed tyres like this due to tyre pressures. I've followed my missus and I can tell you her wagon doesn't crab up the road and if it did I'd expect it to wear oddly on one side only not evenly on both sides which is what this does. Also, if the tyres were under inflated the centre of the tread would be worn less than the outer but this is also not the case as tread wear is even across the the tyre except for the worn outer shoulders.

I agree that stiffening the front is not the best solution and I really don't want to do that if I can avoid it but at this point I'm running out of options if I can't get the missus to budge on touching her car. Ideally I'd like to remove the blooody bull bar and replace it with a smartbar but she'll have none of it which is why I'm looking for a more clandestine way around the problem.


Just so we're clear, the rear end doesn't wander or skip or jump out of line on bumpy dirt roads, doesn't walk on corrugations or anything else untoward. The way the car steers at speed is hard to describe, the nearest I can come is, years ago I drove an early EA Fairmont and it would go from understeer going into a bend to to oversteer at the apex in the blink of an eye, that's how the wagon feels, like it's in a permanent nervous oversteer situation if you try to make a steering correction. I have to be slow and deliberate and precise turning the wheel when cornering on the highway or it oversteers, it can be very unnerving.

[Raptor]

Originally Posted by Bushbasher

...
The way the car steers at speed is hard to describe, the nearest I can come is, years ago I drove an early EA Fairmont and it would go from understeer going into a bend to to oversteer at the apex in the blink of an eye, that's how the wagon feels, like it's in a permanent nervous oversteer situation if you try to make a steering correction. I have to be slow and deliberate and precise turning the wheel when cornering on the highway or it oversteers, it can be very unnerving.

That's the rear steer effect I was talking about. aka Roll Oversteer (Google it)

Originally Posted by Raptor

...
Good chance what are feeling is rear steer due to the raised rear suspension height with the live axle/re-arched leaf springs. To minimise this effect the factory places the front of the rear spring near horizontal to the road. On XR wagons/utes it's even positioned slightly lower at the front for higher speed stability - your's will be the opposite of this. That's bad.
...

As your wagon body rolls side to side, most noticably with big or rapid steering corrections, the rear axle is steering the car. As this is unexpected that immediately requires another steering correction. As so it goes.

A little known fact is that when Rack & Pinion steering was introduced to the utes with the XH models (XG still had a steering box, pitman arm etc) the front mounting eye of the rear springs was lowered to counter this effect. The quicker action of the R&P making the utes very nervous to drive, something that hadn't been so noticable with the slower acting steering box design.

[Bushbasher]

Ok Raptor, I think we're talking about the same thing but with different terminology, basically the rear is trying to come around because it's loading up faster than the front. The solution is still the same, soften the rear or stiffen the front to correct the balance. If she'd let me remove the Bullbar or take a leaf out of the rear springs I think most of the problem will correct itself.

[cheap]

Reading between the lines, the car drives with a nervous feel, strong winds make it run off track, abnormal tyre wear. This is because the front end of the vehicle is lifted it will need camber/castor adjusted to compensate.

[Raptor]

Originally Posted by Bushbasher

Ok Raptor, I think we're talking about the same thing but with different terminology, basically the rear is trying to come around because it's loading up faster than the front. The solution is still the same, soften the rear or stiffen the front to correct the balance. If she'd let me remove the Bullbar or take a leaf out of the rear springs I think most of the problem will correct itself.

Not sure that we are

I'm saying you have roll oversteer due to way the rear of the wagon has been raised. Stiffer suspension and less roll will reduce the effect but brings with it other compromises.

Roll understeer (factory height or lowered leaf set-ups) results in a safe, stable steering feel.
Roll oversteer (lifted like your wagon has been) makes for an unsafe(?) nervous steering feel.

Also, as cheap has just mentioned, if the rear is higher than the front it is taking away front caster which won't help with the steeing feel either.



But that's enough fro me

[snap0964]

There would probably be some bump steer as well, since the front roll centre has been raised - the steering rack arms probably aren't parallel with the ground.

Originally Posted by Raptor

A little known fact is that when Rack & Pinion steering was introduced to the utes with the XH models (XG still had a steering box, pitman arm etc) the front mounting eye of the rear springs was lowered to counter this effect. The quicker action of the R&P making the utes very nervous to drive, something that hadn't been so noticable with the slower acting steering box design.

Ahh yes, that would explain why the std XH's have their own 21:1 linear ratio, while the XH XR utes get the EF/EL 18.5:1 variable ratio.

[Bushbasher]

Originally Posted by cheap

Reading between the lines, the car drives with a nervous feel, strong winds make it run off track, abnormal tyre wear. This is because the front end of the vehicle is lifted it will need camber/castor adjusted to compensate.

The geometry of the car is fine, it tracks straight, is not overly affected by wind at all and the only abnormal wear is the outer shoulders of the rear tyres, it's only nervous when you turn in at speed, especially on an uneven surface when it becomes oversteery very quickly if you're not careful. The front alignment is good and the front wear is as you would expect it to be on any well aligned car, it's just that once you rotate the tyres to the front there is already bad shoulder wear before you start.


Here's a pic of the car, it doesn't sit overly nose down, in fact it has a near factory stance, just 3" higher


mums car 4.jpg




Thanks snap0964, that makes sense but it seems to track ok with no deflection from bumps it's just that you have to use much less input on the wheel than you would on anything set up properly or it oversteers. If I climb straight from my Fairlane into the wagon I find myself having to correct the steering going into the first turn I take, which is usually onto the highway if there's no traffic coming, which is why I said I need to be very slow and precise with the steering input in my original thread. Same for when you hit the bow wave of an oncoming truck, it's very easy to over correct for that little sideways push you can get if there's a cross wind.

[5thFordWA]

Originally Posted by Bushbasher

This is about tyre wear and looking for the cheapest fix I can live with...
.................................................. .
The problem is, the rear is still stiffer than the front causing the car to feel like the front is wandering on bumpy roads plus the rear eats the shoulders off the tyres because it doesn't lean over as much as the front in corners. Rotating them just means the front finishes the job with still 10-15k km worth of tread left in the middle of the tyre. If I don't rotate I'm changing rears at nearly twice the rate of the front because they take the shoulder down to canvas by just over half way through the tread life.
.................................................. .
Cheers
Bushbasher

I can't comment on your theory of why the rear tyres are wearing because I am not a suspension engineer, but speaking as an old mechanic, it is not something I have come across before.
My experience, similar to others above, is that if the live rear axle is not bent, and is aligned straight ahead, then tyre wear is usually very even across the tread, given correct inflation.
In fact my first thought is that it may just be the brand/type of tyre you are running causing the wear problem.

I can only refer to my BA LPG wagon I owned for 13 years. For a reasonable road tyre, but higher load rating for towing, I was recommended and ran through 2 sets of Yokohama A Drive tyres, 99H (high load), on standard 16” rims. They lasted for yonks, like 80000 kms, probably a little hard and I was always pretty careful in the wet, but they served me well. I don't rotate my tyres generally, so I can see what each wheel is doing and monitor wheel alignment as required by tyre wear - my BA never needed changing alignments. It was explained to me that the 99 load rating meant the tyres had stronger/stiffer side walls, but not as much as a light truck tyre.

To the suspension. I like a very standard car, but I wanted a bit more clearance for driving on unsealed roads. I found that King Springs made 30mm higher front coils which I preferred to purchase instead of having someone reheat and reset the standard springs. I took it to a respected suspension dealer in Perth, and asked for him to supply and fit those front coils , and reset the rear leafs by about the same amount. He had very good advice as he had done a lot of these for Main Roads WA apparently. He recommended fitting an extra leaf, but not resetting the original leafs, the extra leaf alone would make it about 35mm higher, and avoided any heat treatment of the standard leafs, also it made it a much quicker and cheaper job. And just that extra bit of load capacity for towing a caravan. All sounded good to me, and that's what was done.

The wagon sat quite level, and in fact most people would not notice it being higher, it looked good. It gave me about 175mm clearance under the front crossmember, and the rear axle had about the same, you cant increase that without going to bigger diameter wheels/tyres.

The car drove well, I did notice it could be a bit skittish in the rear on a bumpy wet road, but that was to be expected, drive accordingly.

Anyway, that is my experience with a similar vehicle.

Cheers.

[Bushbasher]

Thanks for your input 5thFordWA. I can tell you the diff isn't bent and the whole suspension front and rear is still tight and as it should be and the shocks still seem to be doing their job. It sounds like what they did to your wagon is what should have happened here but somebody just went completely OTT on the rear springs by resetting them AND adding the extra leaf. That would explain why it's so high, then they had no choice but to stiffen and raise the front to try and match the back. I've tried le cheapo tyres and Bridgestones, and Dunlops and Supercats and they all do the same thing. I'm going to try and convince the missus to let me remove the bullbar for this new set of tyres just to see what difference it makes. If it cures the scrubbing then I have a good argument to remove the extra leaf in the rear and put the bullbar back on. With a bit of luck, removing the extra weight hanging out over the front wheels will sort out the balance, even if it does ride like a go cart. That being the case, removing the extra leaf and refitting the bullbar should soften the whole show up a bit and make it acceptable.... here's hoping

[Crazy Dazz]

Originally Posted by Bushbasher

Just so we're clear, the rear end doesn't wander or skip or jump out of line on bumpy dirt roads, doesn't walk on corrugations or anything else untoward.

Then you have the only leaf-sprung car in history that doesn't.
I've owned a few Falcons, over several different models, and that was always the shortcoming of the wagon on bumpy unsealed roads.
At one point in history, the family ride went from an XF sedan to an XF wagon, to an EB sedan, to an EF wagon, and both wagons had the same issue.
And as I said, HD leaves could only make it worse.

But that is a digression.

Even with rock-hard suspension, it is hard to imagine it causing that level of scrubbing. Please understand that we've not doubting you, just struggling to envisage scenarios that fit.

Do you have any photos of the wear? I suspect we might not be fully understanding where on the shoulder the wear is happening.
Could you also please let us know what size tyre, rim width and offset, and pressure you're running.
In terms of pursuing "simple" options that you can sneak past the missus, it may be that change in tyre, profile, or even offset, could alleviate the symptoms.

[Bushbasher]

215/60r16. Standard falcon alloy as in the pic above running 32-34psi.


After much haggling last night over red wine for her and CC for me, I finally convinced her to let me remove the bullbar, which happened today before she changed her mind. It has definitely made the car feel more stable and nicer to drive although the front is a little harsh now on sharp edge bumps and spoon drains. I'll get a pic of the tyre tomorrow for you as the car went to work with the missus tonight.


As for the car behaving on rough dirt roads, what I meant was it doesn't and didn't do anything unexpected beyond the usual occasional skittishness you get with any leaf spring rear, in fact, as stiff as it is in the rear, it feels better and tracks straighter than the old AU wagon we used to have.

[janddbone]

Please place approximately 250 - 300kg in the boot and come back to us after a drive...

[78xcgxl]

Originally Posted by Raptor

That's the rear steer effect I was talking about. aka Roll Oversteer (Google it)



As your wagon body rolls side to side, most noticably with big or rapid steering corrections, the rear axle is steering the car. As this is unexpected that immediately requires another steering correction. As so it goes.

A little known fact is that when Rack & Pinion steering was introduced to the utes with the XH models (XG still had a steering box, pitman arm etc) the front mounting eye of the rear springs was lowered to counter this effect. The quicker action of the R&P making the utes very nervous to drive, something that hadn't been so noticable with the slower acting steering box design.

That's an awesome fact. Was wondering why they lowered the front eye on XHs. The fact that XHs also ran a slower ratio steering rack (21:1) compared to EF/EF sedan(18.5:1) only proves this fact even more. XH XRs ran the sedan ratio however. FYI i replaced the XH rack with an EL one and the car drives so much better with the sedan steering rack!

[Bushbasher]

Originally Posted by janddbone

Please place approximately 250 - 300kg in the boot and come back to us after a drive...

Not without putting the bullbar back on to hold the front down. The car is better balanced now but the front is now stiff as well and putting that much weight in the rear will make the front do wheelstands, lol. It's too stiff at the front now too and the whole car needs softening up but the purpose of the exercise it to see if the balance stops the rear tyre wear. If it does then I'll get the extra leaf removed from the rear then put the bullbar back on. It got new front tyres last week and gets new rears this week then I'll see how they wear before attacking the rear springs.


Here is a pic of the rear tyre. This tyre came off the front about 10k km ago and still had it's shoulder.


rear tyre.jpg


The tyre that went to the front was down to the canvas last week after it ate what was left of the shoulder. I've never had any vehicle do that to rear tyres like that.

[BENT_8]

I think whats happening is the stiffer raised rear has lifted the roll centre, and although the front is also stiffer than factory, the bulbar was compensating in corners by exaggerating the balance shift to the front loaded corner.

What it essentially means is that because the rear is stiffer than the front, when the front dips and rolls left for example in a high speed right hand bend the front wants to perform as normal but the rear with a higher centre of gravity isnt rolling on the suspension as its too stiff, so its transferring the exaggerated higher C0fG lateral forces to the tyre deforming the tyre wall, its basically performing like a front end with excessive toe in, scrubbing the outside leading edge.
Now that you've removed the extra weight forward of the front axle the front wont dip and roll as much meaning better balance front to back, but the stiffer front springs are now more evident.

[5thFordWA]

Originally Posted by Bushbasher

215/60r16. Standard falcon alloy as in the pic above running 32-34psi.

I never ran my BA wagon on less than 36psi, and if I was going to do country driving, 40psi.
That, and the fact you are running on unsealed roads, to me, is enough to cause shoulder wear on any tyre.
However, I know you are also comparing this to other vehicles you have had, so it would only be a contributing factor.

Cheers.

[Bushbasher]

Thanks BENT8, that's pretty much what I thought I said in the beginning, you just stated it more succinctly, thanks. The back is too stiff and not rolling when the front does so the tyre is having to do the rolling instead thus eating up the shoulder in the process. All this talk of roll oversteer isn't right because there is no roll because it's so stiff.


The raised relationship of front to rear ride height was no more than any stock wagon except it was 3" higher front and rear. If anything, it now sits flatter as the front has come up another 1/2". Interestinly, the missus said this morning it felt more floaty to her. Once I explained it should feel more like my Fairlane now that the balance is better she agreed that it did, so I'm putting that down to the front being a bit higher now and the steering lighter now the bullbar is gone so she's using too much input.

[Bushbasher]

Originally Posted by 5thFordWA

I never ran my BA wagon on less than 36psi, and if I was going to do country driving, 40psi.
That, and the fact you are running on unsealed roads, to me, is enough to cause shoulder wear on any tyre.
However, I know you are also comparing this to other vehicles you have had, so it would only be a contributing factor.

Cheers.

With 36-40psi how was your tyre wear across the tyre, and didn't you say you ran tyres with a stiffer side wall, that would have to make a difference also wouldn't it? Also, the car is running 90% bitumen 10% dirt or there abouts

[BENT_8]

It'll be more level, but still have a higher centre of gravity, however, the bull bar wont be pulling the front loaded corner down and rebound will have increased.
Before you had a front end trying to roll and a rear end trying to avoid it, basically trying to twist the body shell if not for the rubber tyre wall giving in first.

I still think from a safety perspective in your neck of the woods i'd be putting the wildlife defence mechanism back on and reducing the total ride height instead.

[Bushbasher]

Originally Posted by BENT_8

It'll be more level, but still have a higher centre of gravity, however, the bull bar wont be pulling the front loaded corner down and rebound will have increased.
Before you had a front end trying to roll and a rear end trying to avoid it, basically trying to twist the body shell if not for the rubber tyre wall giving in first.

I still think from a safety perspective in your neck of the woods i'd be putting the wildlife defence mechanism back on and reducing the total ride height instead.

That's the plan ultimately, removing the extra rear leaf should drop the rear a bit and soften it and putting the bullbar back on will lower the front back down and effectively soften it as well, hopefully while still maintaining the balance.