65 replies to this topic

[yel327]

If you plan to lower the UCA months, just use a late LX (non A9X) 6cyl or V8 crossmember and use the UC UCAs and steering rack. Will save you having to cut off Opel mounts (if it is a UC with Starfire they are the same mounts). The rest is essentially the same. If you really want to you can weld some shock absorber metal cups to the crossmember (copy off UC). I don't know if there is 25mm each side difference between HQ-WB rotor and stubs versus Torana/Sunbird stub and rotors. I might be wrong but i'd have thought it closer to only a small gain.

 

I'd not hesitate to use the HQ-WB stubs and rotors, with any luck you'll get some PBR calipers with the UC and with the right pad carriers it is a straight bolt up. Just use at least UC steering arms as already said.

Edited by yel327, 05 November 2016 - 12:40 PM.

[orangeLJ]

Have a read of the UPC brake thread here on the forums.

Bit hit and miss from memory

[ls2lxhatch]

Power steering is worth considering as it will reduce the number of turns from lock to lock.

 

 

HQ stub axles do not make a significant difference to track. The track alters as the lower control arm (LCA) moves up and down. When the LCA is horizontal track is at its maximum. Track reduces as the arm moves away from horizontal. There will be a small difference in track between HQ and LX stub axles with the body at the same ride height due to the different angles of the LCA. This could be a small increase or small reduction depending on ride height.

 

 

HQ discs on LX stub axles or HQ stub axles do not do not make a significant difference track.

 

 

The Hopper Stoppers 290 mm kit for Torana stub axles used to be available in two versions. The standard offset version did not alter track and the Commodore offset version increased track by 16 mm (8 mm either side). I am not sure if the standard version is still available as it required a different hub to the majority of the Holden brake kits.

 

 

The Hopper Stoppers 300 mm kit for HQ stub axles is only available with the 16 mm increase in track. The increase is required so the brake caliper will clear the taller caliper mount on the HQ stub axle.

 

 

[axistr]

Even with UC upper control arms and a good straight k-frame, 1 1/2 - 2 degrees positive caster is about it with out destroying the camber. Negative camber reading below 3/4 degrees static isn't much good unless you intend on doing fast track work. You would be better off making the lower inner control arm mounts adjustable. With caster reading above 4 1/2 degrees would give you much more cornering camber gain then repositioning the top arms, much quicker return to centre, more steering feed back and should give the steering a better toe out on turns. Don't forget K.P.I also makes the steering return to centre.

 

The only down side is you may need a gym membership to improve the arm muscles if you intend on using the manual rack, and a bit of guard trimming in front of the front wheels may be needed/ 

[76lxhatch]

If you're talking about offset bushings for the lower control arm, I modified some Superpro ones to fit an old pair of (modified) Commodore IRS offset crush tubes:
http://www.gmh-toran...e-8#entry849759

I didn't bother with the anti-dive in favour of maximum camber gain, since its very limited without more significant modifications. Managed to achieve around 6.5 degrees of static caster anyway.

I believe there is a thread around here somewhere regarding brake clearance issues with Convos. Problem is you can't get decent tyres for smaller wheel sizes either, kind of need at least 17s to get a good enough tyre to take advantage of the suspension improvements :-(

[Toranamat69]

Very interesting stuff.  I haven't tried all those combos and I have tried a few different ones using the A9X stubs and steering arms but your results look very similar if not identical to my measurements.

 

I have built a bit of a cant into the top control arm also - I went for 3 degrees but I can't remember how much lower that made the mounting hole, but I don't think it was 19mm, maybe half that, Id have to check to be sure.  I was looking for close to constant castor through the range whilst using 6 degrees static castor.

[76lxhatch]

Unfortunately bump steer figures are a bit useless unless you have it close to final static alignment settings, it just makes too much difference (as does the steering arm used). Absolute figures would also be nice to see where the caster and camber zero points are in relation to each other.

There are as many supporters of toe out bump steer as toe in. Some of the Locost and similar forum posts make interesting reading.

Some crossmember measurements here:
http://www.gmh-toran...member-rebuild/

[N/A-PWR]

Seen in a 2006 thread,

 

 a guy say that HX stubs has better steering geometry.

 

 

I don;t know.

[axistr]

I would be sticking close to the UC setup due to the relatively low camber, caster and toe movement from neutral. The more change you get in any direction from ride height will give the vehicle a tendency to wallow around high speed cornering. If its track work only your after then stiff suspension and anti roll bars are properly what your after and you may not get that huge camber change your after with longer ball joints ect. in the right direction. I  know we are still all playing around with old design front ends so its hard to compare with vehicles like M3 & C63AMGs but if you look at these cars they rely on big camber changes through high caster settings. The tighter the corner the higher the camber gain you get, its nice and progressive.

 

If you add lots of caster using the A9X arms would be the go to try and compensate for the roll upward of the steering arms. I did some graphs some time ago, A9X arms and UC stub axle and still retained good numbers between 5 & 6 degrees positive caster using the lower control arm mounts to change caster/camber. More positive caster can help reduce the amount of negative camber you need and you will get better front end braking due to the better tyre foot print on the track surface. Most of the hard braking is done before hard turn in.

 

Its important to remember a bump steer curve is not just about toe change, any change in alignment angles due to suspension travel can give the vehicle a tendency to go in an unwanted direction.

 

HX stub axles also have  different K.P.I The higher the K.P.I the more self centring effect you will get. An interesting fact, I supplied a power steering rack to a customer a few years ago for track racing and Targa. They reported saying on tight closed circuits the car was 2.5 seconds quicker per lap with power steering many due to be able to down shift and short shift during hard cornering which they previously couldn't due as they needed both hand on the wheel to pull it through corners.               

[axistr]

Chev with serpentine belts.

 

 

 _20161126_155422.JPG   335.36K   6 downloads