63 replies to this topic

[ls2lxhatch]

A9X RTS. Used UC type upper arms, arms mounted high again (I think) and LX rack but rubber mounts replaced by solid mounts (alloy from memory).

 

I believe the A9X had the upper control arms mounted in the lower position. Basically a UC k-frame with holes drilled for the A9X.

 

I think the reason for this is that the A9X stub axle lowers the car around 20 mm so moving the arm down from the UC position restores the angle of the upper control arm to around the same angle as it is on the UC suspension which is roughly horizontal at ride height.

 

This is a picture from a previous thread posted by dangerous. I photo shopped the measurements in based on the discussion.

 

Edited by ls2lxhatch, 14 August 2013 - 10:28 PM.

[76lxhatch]

... the A9X stub axle lowers the car around 20 mm ...

 

Not to mention being taller than the standard Torana stub axle also, apples and oranges with the upper arm positions

[yel327]

So the A9X retained the LX RTS upper control arm mounting position/height? I did say "I think"!!

 

Not sure how the use of HX-WB stubs (which lowers the car) affects the angle of the arms though. Stubs are the same height from lower to upper balljoint, just the axle sits higher on the stub giving the inherent lowering of the car. Upper and lower arms should remain in the same position shouldn't they?

 

Didn't GMH simply lower the upper arms at the introduction of RTS in LX to alter the front end geometry a bit? And to do it properly they needed to change it further by shifting the caster angle by moving the upper balljoint backwards which is what the A9X ad UC upepr arms do.

[76lxhatch]

Stubs are the same height from lower to upper balljoint

Pretty sure they're not?

[yel327]

I'm pretty sure they are. I remember putting them side by side years ago and the only obvious difference between HK-WB and LH-UC was the location of the axle, although I know that ther are other minor differences too like KPI and caliper mount. It is an old memory I must admit though.  

[76lxhatch]

Left one is HQ-WB, right one is Torana

[76lxhatch]

But the measuring tape says both are approximately 198mm from top to bottom, so its just an optical illusion - my apologies! Strange that I've always though the HQ ones were taller even having had them side by side

[Marks LXTorana]

This is all great feedback thanks everyone. Can anyone post images of the rubber mounted and solid mounted steering rack for comparison?

[yel327]

It is obvious when you see it, the oddball one is A9X where the rubbers are replaced by metal bushes.

[Marks LXTorana]

It is obvious when you see it, the oddball one is A9X where the rubbers are replaced by metal bushes.

Yes, that was the image i had in mind. So the solid mount is as simple as not having rubber bushes, more or less?

[ls2lxhatch]

Not sure how the use of HX-WB stubs (which lowers the car) affects the angle of the arms though. Stubs are the same height from lower to upper balljoint, just the axle sits higher on the stub giving the inherent lowering of the car. Upper and lower arms should remain in the same position shouldn't they?

 
When you fit the A9X stub axles the car is lowered around 20 mm compared to the standard suspension. To restore ride height on the A9X a taller spring is fitted to raise the suspension which causes both the lower and upper control arms to swing down. Moving the upper control arm pivot point down around 25 mm will restore the upper control arm into roughly the same position as it is on a UC at the same ride height.

The A9X also had a bump stop welded to the k-frame to limit the compression travel back to the same as the standard Torana.

 

[ls2lxhatch]

The larger diameter A9X tyre would make up for some of the height lost due to the stub axles.

 

However they still extended the bump stop by a significant amount. Judging by the pictures the bump stop is bigger than can be explained by drop stubs and tyre diameters. The bump stops on the diff were also extended.by more than I think can be explained by tyre diameter.

 

It would be interesting know exactly how much larger the front and rear bump stops are on the A9X compared to the standard Torana.

 

The larger bump stops may be there for flare/guard clearance on the track cars.

[76lxhatch]

Even then they (race cars) would still be smacking up the bump stops.

 

That's visible in the photo above too, it looks to have been on them pretty hard. That can't help handling much!

[Dr Terry]

LX SL/R's had front and rear too.

 

Note: They're anti-sway bars people, they don't make the car sway, lol.

 

s

Picky, but correct !!

 

A bit like 'pollution gear' it wasn't fitted to add to pollution, it was actually anti-pollution gear, it was fitted to reduce pollution.

 

Dr Terry

[ls2lxhatch]

Even with the std A9X springs the bottom A9X LCA's are still level ,as are UC's with the appropriate steering arms correcting for the stub axles used (bump steer).

 

The L34 and A9X were fitted with F71 heavy duty spring package as standard. The F71 heavy duty spring package was available as an option on the standard Torana.

 

The F71 spring increased the clearance between the bump stop and k-frame at ride height by 15 mm  from 59 mm to 74 mm. The actual ride height would increase by more than 15 mm due to the location of the bump stop.

 

If the LCA is level on a UC with standard springs then it cannot be level with A9X springs. If the UCA pivot position is optimal with standard springs then it would need to be lowered for F71 springs.

 

 

Edited by ls2lxhatch, 16 August 2013 - 12:49 PM.

[ls2lxhatch]

According to the service manual replacing the standard springs with F71 springs will raise the suspension ride height increasing the gap between the bump stop and k-frame by 15 mm.

If you alter the suspension ride height then obviously you change the angle of the LCA. The LCA cannot be at the same angle on a car fitted F71 springs and the same car fitted with the lower standard springs. Whatever the angle of the LCA is on a A9X the angle of the LCA on a V8 Torana that weighs the same with standard springs will be different.

If you alter the suspension ride height then you may need to revise the whole suspension design, at a minimum you would look at moving the UCA pivot point.

Edited by ls2lxhatch, 16 August 2013 - 10:35 PM.

[76lxhatch]

Had the A9X LCA with F71's been pointing down they would have went into poor bump steer situation in the first 1.5" of travel as the arc went from positive to max radius to negative.

 

I don't see how that's true, with the assumption that the steering is properly set up to minimise bump steer throughout the suspension travel. Having carefully measured it on my own front end for the power steering conversion and being pleasantly surprised that it is quite minimal for the era, add the fact that Holden went to the trouble of casting the special steering arms for the A9X and I think its a reasonable assumption.

 

I have heard this theory before about the lower control arm and tie rod being level at ride height, but I can't see any direct steering correlation other than maybe a good spot to eyeball the relationship between the two, or possibly it would have an effect on bump steer in older vehicles with poor bump steer characteristics to begin with. It does seem like the starting point of the lower control arm might affect the lever action on the spring I suppose but that's a different issue.

 

The picture above looks like it comes from an Ellery manual so I wouldn't put too much faith in it either. However the basic premise that the heavier spring pushes the lower control arm further down has to be correct, as the cross member doesn't move. It also needs to bring the stub axle down to cater for the drop stub effect if the car is to remain at the same height as with a Torana stub.

[yel327]

The L34 and A9X were fitted with F71 heavy duty spring package as standard. The F71 heavy duty spring package was available as an option on the standard Torana.

 

The F71 spring increased the clearance between the bump stop and k-frame at ride height by 15 mm  from 59 mm to 74 mm. The actual ride height would increase by more than 15 mm due to the location of the bump stop.

 

If the LCA is level on a UC with standard springs then it cannot be level with A9X springs. If the UCA pivot position is optimal with standard springs then it would need to be lowered for F71 springs.

 

 

 

That makes logical sense to me.