VS IRS question

[hotwyr]

Hey all, brand new member here, and i'm gonna straight up say that my knowledge with cars has some key holes in it. But that's why im here, to learn by asking.

So here's my question. I've heard some interesting stories about the IRS system in the commodore, such as wheel fold when sliding through a round about (nasty crash followed, rollover 6 times, lucky they survived). Now a good friend of mine, who was a Holden mechanic for 3 years and has been in more than 1 accident caused by IRS wheel fold, has told me that the issue stems from the fact that the IRS on commodores doesn't have an upper control arm.

Now I don't plan on going out and doing burnouts all night in my commo, thats not my thing. I'd just like to be able to slide (at a track of course) without worrying about a rear wheel folding under the car and me going into a tumble. I'd like to prevent that at all possible :P

So i've looked around. In my searches I saw someone say that you could swap out the old IRS system for a more modern one (I'll get back to this). I also found some very helpful pics that illustrate the system quite well.

here's what i see, the commodre IRS system:
That is In fact missing the upper control arm.


Another one, again missing the upper control arm.

But then I came across THIS photo: This IRS system does IN FACT have upper control arms.

So, in the sense of preventative maintenance (reducing the chance of my baby ending up on its roof ) I was wondering, what options do i have to install upper control arms into my IRS system? What model's of commodore had an IRS with upper control arms? What system is that last photo from?

Help would be greatly appreciated, thanks

[bandit10]

ive never heard of this problem? and those diffs pictured are not vs commodore diffs.

[hotwyr]

ive never heard of this problem? and those diffs pictured are not vs commodore diffs.

I've heard of it a few times. As far as i know it happens when you put huge amounts of sideways load on a wheel (sliding excessively), and due to the lack of support.. well, you get the idea.

As for the photo, well it was a post here in Justcommodores and the poster stated that it was a VS commodore IRS system, but i've seen them and it looks nothing like it. I was thinking maybe it was from a later model??

[bandit10]

110% defo not VS IRS, i have a VS SS with IRS and it looks nothing like that.

That photo has been used a lot on here to give an example of the different look between IRS and live axle as it has both pictured.

[stocky]

Is that a VE rear end?

[hakhawk]

pic above is the irs from a mustang. the live axle diff is too i believe

[Brett_jjj]

These are from a VS.The top pic is the IRS setup.The lower pic is the solid rear axle setup.

[BlackVXGTS]

I have run hundreds of racing laps in my IRS VS Calais at Murcott high performance days without any problems from my rear (or front) suspension.

[hotwyr]

Thanks for the comments.

I did a bit more searching around and i found something. Turns out the VX onwards has upper control arms in the IRS systems plus some other goodies to make the whole cradle better. Can I install an IRS cradle from one of those models into a VS? Would it be a straight bolt in? Or would Modification be required due to the added components in the cradle?

I know some of you have had no issues with your IRS systems, but it's more of a peace of mind thing. Like i said before, preventative maintenance.

[RX25SE]

I've never heard of wheels folding on Commodores with IRS.......or any Holden for that matter.
Side loading on the rear suspension assembly would be LESS when in a slide as the TYRES HAVE LOST TRACTION.
Maximum side thrust would depend on speed, turning angle, tyre grip etc. and would be at a maxiumum just before the tyres let go.

From memory VX does not have upper control arms, still the same old semi trailing arm (kinda like BMW from the '80s) but with 'Toe Control Arms' added to prevent toe changes as the arms swing through their arc as the suspension rises and falls. They compensate for delfections in the trailing arm pivot bushes.

[vn_v6]

any axle or suspension will fold if you hit a gutter..........