Suspension

[FamiliaGTRAe]

Hi,

For those of you who owned both an AU and a nice new BA, is there a major difference between the two types of suspension on the road?

I was always led to believe that the AU IRS was a good unit, and was miles infront of the Expensive Daewoo semi trailing arm with extra bit, suspension. Which leads me to think that the BA IRS must be even better that the AU and therefore the Expensive Daewoo type.

On TV you see Mr Skaife crapping on about corners are made for it, and babies in prams whizzing around (well maybe not under our new don't show naughty Car ads on tv ) yet I can't see how Expensive Daewoo has gotten the "Image" for handling.

Apart from my Datsun 1600 (which had arse sag) I've never owned a rear drive IRS car, all the others have been AWD or front (with IRS) so im curious as to how 220 kw (AU XR8) vs 240kw (XR6t) with the two types of rear suspension went.

Cameron

[bdennis]

Cameron,

I had a AUII XR6VCT (with IRS) before the BA XR6 Turbo.

The AUII handled very well and towed like a dream. I could sit on 110km/h (in a 110 zone!) towning the van all day. The rear of the car hardly moved when I put the Van on the back!. It went around corners well, and it did not rub our rear tyres like the "Other" brand. My only complaint (if you could call it that) was it was a bit clunky and noisy over bumps.. Apart from that. A great set up..

Then there is the BA... I have not towed with it as yet but.. I think it holds on better and is ahead of the allready great AU IRS system. It is not noisy and is as soomth as silk!..

It is all typical for Ford. They may not be at the bleading edge when it comes to releasing something like IRS.. BUT you can bet it will be the best there is in a OZ produced car when it does come.. (thinking music... IRS, Dual Overhead Cam 6, Quad Cam V8, VCT, Dual VCT, Traction control, etc, etc, etc)

Geez its great to be able to own and drive these things.. Would not be dead for quids! :auto:

[Turbo6man]

I have driven both extensively - the AU rear end is actually a bit better IMO. But it is heavier, and that is the main reason Ford designed a "new" IRS for the BA. Also I think it, the control blade IRS, is more space efficient forward of the axle, which was important for Ford in relocating the fuel tank to be within the wheelbase.

[Mals BA XR6T]

I owned the AUXR8, and upgraded to XR6T.

Had both cars on the track, and I must say that the AU was more reassuring (at first) than the XR6T. The reason I say that, is because you can judge how quick you can take a sweeper straight away with the AU. The BA feels like it's going to lift up, or take the weight from the inside wheels, and just as you think 'Oh, sh*t, I've come into this one too quick' the BA seems to rectify itself... don't know why?? But once it does it then feels better as it goes through the corner.

Also the AUXR8 was better for feeling understeer, however at saying that the XR6T is able to come into the corner much quicker.

So in short, I think once you are use to the BA characteristics it takes the corners better, you just have to trust it will behave itself :lol:

Hope this helps

[plonky]

I have been driving the AU XR8 in a profesional capacity for the past 4 years and now the BA in both XR6T and XR8 form.

There are a number of things to consider.

Firstly the chassis rigidity is chalk and cheese. The AU is much looser than the BA and as such, allowed the chassis to flex thus limiting the ability of the suspension to work to it's full potential. The Dunlop SP9000 tyre also had a tendency to tramline at the 3/4 to 1/2 worn mark. The steering was lighter than the BA however it had more turns lock to lock than the BA. The biggest let down on the AU was the softness of the spring rate and the shock absorbers. They were OK up to 120 but after that they became very loose which allowed a 'wallowing' or 'porpoising' effect on normal country roads. They might have handled well on smooth hotmix but they were very unnerving at high speed on normal roads. The mere fact that Highway Patrol Police changed their order to the SS is testament to the high speed stability of the car.

In saying that, I found (because I ONLY drove the XR not something from Brand Crap) the chassis and suspension geometry was very talkative. Even though the car moved around alight it certainly let you know if it had a tendency to push or become loose in a corner, well before it happened, and thus became very controllable and correctable.

Both the XR6 T and the XR8 are a huge imrpovement over the AU. I preferred the XR8 due to the large amount of torque equated to INSTANT acceleration especially from 'point and shoot corners' and 'stop - go - stop - go' corners. The high speed stability is marginally better than an SS and the car will always track true though a corner with minimal wallow or lateral acceleration.

The quicker ratio of the steering rack on the BA takes some familiarity but for those that are used to quick rack European cars it is an easy transition. The BA appears to have more anti-dive/squat in it's geometry than the AU and the heavy weight of the car is a boon at high speed (allowing inertia to overcome strong sidewinds and road faults)

I believe that the AU rear suspension is a 'classic double wishbone' rear end and as such is technically superior to the BA rear suspension. However the BA suspension has the advantage where it can be tuned for a bit more comfort and use the polyurethane bump stops as the inital resistance to longitudinal movement. I think this is why the BA appears more supple but is more controllable. I like the idea and I think it works.

However the advantage the BA has over the AU is that FoMoCo Australia may have been approved to raise the high speed testing benchmark from 130KMH to a much higher speed after approval from FoMoCo US. This is why the BA handles so well at high speed, whereas with the AU they were restricted to a much lower limit by FoMoCo US.

I believe that the AU with the right spring rate/damper ratio, adjustable camber/castor setting on both front and rear suspension, and a bit more chassis stiffening, would be a much better handling car than a BA. This would involve a change in springs, shocks, fitment of a camber/castor kit, retention of the 17' wheel and a tyre such as the Dunlop FM901, as well as a seam welded body.

All this would depend on what you wanted the car to do and whether handling/grip was more important than comfort.

After all, I would like to think that the XR series of Falcon is purchased because it is a performance car with high degrees of handling, stopping and acceleration not because it is a sport car to take the family in comfort for long drivers or just to relive life as a 20 year old when in fact you are 55 approaching 60.

I think this is why the SS is bought by 25 to 30 year old and I would hope that the more performance orientated man buys an XR to sample some real "Total Performance" (as Lee Iaccoca once said in his press release back in 1964)

[Mondie]

Great read Plonky, your job gives you an excellent first hand insight into how these cars peform at high speed.

More informative than anything l have read in any of the mags in years

[FamiliaGTRAe]

Yes thank you very much, I've always been intrigued as to the performance potential of say a AUxr8 and now BA xr8 fitted with everything as per AU / BA except for having the mighty 351 cleveland ( circa '71) and stuff the pollution and the noise levels.

[plonky]

Having a distinct advantage of the circuit at Goulburn which is designed with 15kmh to 45kmh corners, positive camber bends and good power down corners onto the main straight cetainly helps. The fact that the circuit is very narrow and cars circulate in multi directions instills the driver with the necessary skill and appreciation of a particluar vehicle.

I can guarantee you, driving fast and smooth, staying in you own lane, being concious of the traffic lights and various Stop signs as well as having other cars drive towards you in their own lane, necessitates a good handling, stopping and controllable car.

I have only just returned from Goulburn two weeks ago after having two days evaluation in the BA XR8. I have previously done the same thing with the Turbo. The BA was a gem on both the circuit and out on the open road which has broken surfaces and a lot of camber changes in the roads.

There is a significant difference between roadtesting a car on a smooth hotmix circuit or you favourite stretch of backroad and evaluating a car which will be used in all types of weather, road condition and changes in daylight/night.

For a standard production car that can be bought by the public, the BA XR8/XR6T (as well as the AU XR8) are absolutely sensational motor vehicles that are driven very hard, cop a lot of constant acceleration and remain reliable and safe. Naturally consumables such as tyres and brakes are used at a lot higher rate but normal people don't have to drive these cars like HWP Police do.

[Guest HocuSChrisT]

In Regards to Suspension...

Has anyone lowered their vehicle and found any dramas or comprimises in doing so?

[plonky]

I haven't lowered an XR but if you do you must realise that everything changes in the geometry of the suspension.

My advice would be to have someone like Pedders do the job, but with double wishbone type suspension the most effective way to lower it would be to leave the springs at the same length and relocate the wishbone mounting points. This is how Carroll Shelby did it back in the '60's and how most professional suspension engineers do it now.

Good luck with it, but personally the ride height is pretty good as it is, the roll centre remains at the best compromise and you would benefit by different rate springs/shocks as well as un upgrade in diameter to a 17" or 18" wheels with the appropriate tyre to suit the standard overall diameter wheel so as not to change your speedo calibration.