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I am buggerising around at the moment trying to fit a VL Commondore Turbo front strut into my GK Sigma project rally car. Have gone with VL Turbo (same as VP SS) for std BIGGER brakes and obvious availability of performance parts (ie Slotted/crossdrilled rotors, coil over conversions etc etc ) So far conclusion is - The strut itself is of very similar lenghth etc, the lower control arms are the same length and inner bush has the same ID. The sigma top strut mount will fit the commodore strut allowing bolt up. The steering link off the bottom of the struts are the same length as well. The 2 issues I have are - tie rod end sizes are different (trying to source a tie rod end that will fit) and castor rod. I think I can overcome the castor rod by reinforcing the commodore lower control arm and drilling to suit Sigma castor rod. Anyone else had a go at this, or can offer suggestions?

Road legalities could be questionable but as this is going into a Rally car, mods are allowed.

Would it be easier to stay with the standard Sigma struts fitted with Commodore shocks (to simplify the steerings issues) & fit coil-over platforms. This is what I have done to my rally Sigma. If you still want Commodore brakes, then adapt a new disk brake mount, but then you have a 4 stud to 5 stud issue.
Another simple way is to use Starion struts, which already have vented rotors as standard. These bolt straight in, only requiring some camber & castor correction.

You're right it would be easier to go down the Starion strut path, but I like the idea of "off the shelf" sourced parts. As in another post, to get Starion rotors you have to import from the states. With the Commondore option I can phone RDA and have all brake parts here the next day As far as 4/5 stud issues go, i'm not fussed as I was looking to run 15" rims anyway so Commodore steel rims (dime a dozen) here we go. I have sourced a Hilux diff to swap in and will have the rear hubs redrilled to suit commodore pattern.

Thanks for the suggestion Panda, and if it all gets too hard with this swap that's the path i'll take.

Sounds like a good idea in your first post.

Commodore stuff is ridiculously cheap and easy to find. The best part about commodores is parts availability(everything else pretty much sucks).

can you not use the tie rod of the commodore and mod your drag link
thread and just make a castor arm to suit
cheers stealth

I was trying to aim for "off the shelf" parts without having to custom make too much stuff ie drag link etc. If I can acieve this, it will save having to get spares of custom made parts that I may never use (sorry, break ) it will also make it easier for anyone else who wants to try this out as I will list part No's etc used.
Instead of modifying the lower control arm I will get the castor bar from the Commodore modified (its too short and angle isn't quite right) but it is heaps bigger in diameter than the Sigma and Commodore front Castor bush looks to fit.
I have the strut sitting in place now, had to make a 50mm spacer between the sigma top strut mount and the Commodore spring seat, easy as. Clearance looks ok too for 180 deg rotation of top mount for easy neg camber. Just have to pick up a wheel and tyre this week from a mate to check wheel offset!!!!! If that looks ok, off to the engineers for a castor bar.

What ever happened with this conversion??

Exactly as per your pic.......

Started getting a bit messy with too many custome made parts for Rally application. I was going to have to have too many spares made that I may or may not use, so could have ended up with one offs sitting in the shed doing nothing. Also picked up 10 wheels (4 stud pattern) for a slab and putting a Scorp diff in, instead of the hilux as originally planned. I have decided I will go down the path of Starion struts instead.

Don't get me wrong, it was an achievable conversion but in the end just didn't suit.

Hey, thats cool man. Was an interesting conversion though. Would have liked to see it done.
Has anyone measured up a Commodore "K" frame? Would that graft into a Siggy? Would give you rack and pinion steer too.

Theres a Sigma speedway car on the sunshine coast with a complete VL K frame struts etc: Ive had a look under it and it looks factory ..must have been an easy conversion.

Holden did also have a couple of Commodore test mules running a 2.6 Astron engine before they decided to go for the RB30. Imagine if Holden had decided to go with the Astron 2.6 instead, would that mean that the VL Turbos would have 2.6 Turbo Astron engines? Imagine all those cheap extra parts we could've had for our Sigmas lol