40 replies to this topic

[76lxhatch]

Dropping the upper control arm mount clocks the arm so that suspension compression from there will have better (negative) camber gain. This is good, but depending on your ride height it may give you a little more static negative camber, and you've already got a couple of extra degrees from changing to HQ stubs.

It doesn't hurt to drill the extra holes so if it were me I'd do that, then once its all together at ride height do the wheel alignment. If you have too much negative camber then you may find you can dial some out by swapping back to the original holes, and this can be done in place.

[76lxhatch]

As a general statement without knowing specifics of your car or what you're looking to achieve, yes you would use the UC upper control arms in the lower position, and the UC steering arms with some extra positive caster. The non-RTS cross member won't allow you to re-drill the upper arm mounts as easily because they are somewhere in the middle; the UC holes are high so there's plenty of meat left low, and the LX RTS has them low already.

Keeping the Torana stubs helps with the camber issue I mentioned above, they have an extra 2 degrees odd of KPI built in. The HQ stubs lower the car a bit without changing control arm angles, and have a bit more meat on the upright.

As far as steering rack goes opinions differ a little and its more about personal preference. The earlier rack is slightly quicker ratio but the UC one is solid mounted and the extra ratio can help reduce steering weight with big tyres and more positive caster.

Provided the brakes don't significantly alter the track and you achieve suitable clearance they don't directly affect the suspension or steering.

[76lxhatch]

Ah, someone who is actually interested in going around corners! I've spent a bit of time on the front end in mine, on and off over the years, mainly with high performance street use in mind. Its now at the point that it handles reasonably well and can safely carry a fair bit of speed through corners if so desired.

I have the Hoppers 290mm front brakes, with UC control arms and steering arms. I do have a power steering conversion which changes things a bit, including reaming the steering arms to set the most ideal tie rod end height - details in these threads, some of it may be interesting even if you're not changing the rack as it shows how simple things like alignment and ride height can affect the result:
http://www.gmh-toran...ng-alternative/
http://www.gmh-toran...and-bump-steer/

With the upper arm shimmed as far back as it will safely go, and a custom made offset bush in the lower arm, I have achieved roughly 6.5 degrees of positive caster while keeping the negative camber down to around 0.6 degrees. Add some half decent tyres (255/40R17), a good set of Bilstein dampers and a few other bits and pieces, and it begins to work while still keeping the majority of the original components. My project thread has some more info:
http://www.gmh-toran...87

For more general theory on suspension setup and handling (especially with respect to track work) the pro-touring.com forum has some excellent topics written by guys with a lot of experience.

[Bigfella237]

Many thanks for the link to the pro-touring.com forum 76lxhatch, so much information over there, looks like I have some reading to do!

[76lxhatch]

Yep there's many hours to be lost on that forum, you start to get a bit sick of Camaros but I really like the pro-touring idea

[Bigfella237]

I've been reading (and re-reading) the sticky threads on suspension over on that pro-touring forum with information mostly from Ron Sutton, who sounds like he knows what he's talking about.

 

He says he likes to set his castor 1 to 2 degrees over whatever his KPI is to get the desired amount of camber gain on cornering, a Torana spindle has around 9° KPI (at -1° static camber I believe) so the magic castor number would be roughly +10°30'

 

Have I got that right? That's a mega-amount of castor and going by what 76lxhatch said above, probably not possible on a Torana using standard control arms? Plus, power steering would be almost essential or you'd end up tearing the column off the dash trying to turn corners!

 

Swapping to HQ stub axles makes a little difference with the KPI coming back to 7°30' meaning the magic castor figure comes back to +9° but less KPI means a greater scrub radius and we do like to bolt big offset wheels to Toranas so I'm not sure that's such a good thing?

 

This got me thinking, what are the 'perfect' wheel offsets required to achieve a zero scrub radius with each of our spindle options? I assume factory rims would be close so I guess what I'm really asking is, how far away are we with wider rims?

 

We could work it out fairly easily if anyone has the wheel alignment data recorded from their car, we need to know what spindles you're using (Torana or Hx), what offset your rims are, and what your static camber is set at?

 

EDIT: Sorry, of course we need to know your existing scrub radius as well?

Edited by Bigfella237, 01 March 2015 - 02:14 PM.

[76lxhatch]

I believe that is what he is saying, but its in combination with everything else and assumes the more modern suspension setup approach, rather than something traditional.

My scrub radius is quite large at approx 93mm positive. That is with a +3 offset wheel which has a rolling diameter of approx 635mm; the offset is wider than most which increases the scrub, but its also taller than many which reduces it a little. The only way to modify your scrub radius without significant re-engineering of the suspension is to change the wheel offset - aside from clearance this is why you will see a lot of cars with big dished wheels on the back but not on the front (which looks awful but). Take a look at later model Corvette stubs and wheel offsets to see an example of this (without resorting to MacPherson struts). You will need a very positive wheel offset to achieve zero scrub radius on a Torana, probably more so than a Commodore wheel, which is unlikely to be practical.

You do not want zero scrub radius in real life; small movements will always pull it positive or negative, and at zero there is a high likelihood it may do both which would result in a kind of shimmy or death wobble. The accepted modern idea is to have some small amount of negative scrub radius, enough so that it will never transition beyond zero (i.e. to positive). And having it negative means that any pull due to scrub is inward, which is generally safer than outward as it doesn't have as much unwanted push effect on the steering gear and is less inclined to tramline. This kind of setup is what you'll see in a late model MacPherson strut Commodore.

A Torana came from the factory with a positive scrub radius, as with many American cars up to the same era. While not necessarily ideal its generally designed to handle this, and will certainly handle higher positive scrub radius than if you put wide offset wheels on a Commodore (most will know the tramlining effect this causes). The OEM scrub is unlikely to have been as high as the numbers I have quoted for my car, but when all was said and done my research and testing had me satisfied that keeping total positive scrub under 100mm was OK.

Disclaimer: this is my opinion based on my research and testing, specifically applied to my own vehicle. Some comments may be simplified.

[Bigfella237]

A change in KPI changes the scrub radius, so swapping from Torana stub axles to A9X will reduce the KPI and therefore increase the scrub radius, which is a bad thing, however he says in the article that scrub radius isn't super critical unless you're doing very tight turns such as when doing autocross events and that he will often sacrifice scrub radius for wider wheel track.

 

After posting above I went back and re-read the part about KPI/Caster Split and it does say he likes to see a figure 1 to 2° over KPI for the total castor, the total being the sum of the static castor plus the castor gain at full compression. So if you are able to achieve +6°30' of static castor with the A9X spindles, then you only need an extra +2°30' of castor gain as the suspension dives to arrive at his "magic number".

 

Caster gain is achieved when the control arm geometry is set for anti-dive. That means, as the suspension compresses, either the upper ball joint centre moves rearward as it travels up, or the lower ball joint centre moves forward as it travels up, or a combination of both. This is achieved by mounting the upper control arm pivot higher in the front & lower in the rear, creating an angled travel, or by mounting the lower control arm pivots lower in the front & higher in the rear, creating an angled travel.

 

I'd love to have access to a wheel alignment machine, I'd set the car up then remove the springs & shocks so we could measure the angles through the full movement of the suspension just to figure out how much needs to be done, but in the end I guess you're pretty limited with the factory components as to what you can change.

 

Re-drilling the UCA pivot points would be the biggest thing you could change, followed by your offset LCA bushes, but after that you'd have to start replacing control arms with custom tubular stuff?

 

All very interesting reading anyway, now looking at rear suspension setup, he basically says that the non-adjustable triangulated 4-link setup we have is good for picking the kids up from school but crap otherwise...

[Rockoz]

Didnt Lenny (axistr) do the full steering geometry thing while he developed the power steering?

[76lxhatch]

A change in KPI changes the scrub radius, so swapping from Torana stub axles to A9X will reduce the KPI and therefore increase the scrub radius

Yes but its not a lot, to get to a near-zero/negative scrub would require a lot more changes.

plus the castor gain at full compression

There isn't really any to speak of with a Torana. I have wondered about using the Camaro-style anti-dive by tilting the upper control arm, but it would reduce the improvement in negative camber gain achieved by dropping the mounts if one stayed high, and I think the Torana needs that.

I'd love to have access to a wheel alignment machine

Its not hard to do, my setup involves a three legged plate to sit against the wheel with a cheap laser pointer mounted to it, plus a digital angle finder and a few easily made bits and pieces to help position things. Wheel turning plates just need to be a couple of pieces of something with grease in between. Can get some photos and post some more details if you like, its a bit slower but works just fine. Caster is easily calculated from camber measurements at different steering angles, an expensive machine just does this automatically. Most alignment places have fixed pricing only and won't allow any time for tweaks, plus they get confused when you want specs outside what their computer lists.

Didnt Lenny (axistr) do the full steering geometry thing while he developed the power steering?

I believe so, I've done the same myself. As I said above though, any numbers apply specifically to my vehicle. Just changing alignment shims can make a massive difference, not to mention wheel and tyre offset and diameter.

[Toranamat69]

Interesting thread guys.

 

I started out measuring castor gain, bumpsteer, camber gain etc for every combo I could think of using Torana and HQ bits and after market bits and the work is enormous.

Using the manual system, every chart is a huge number of measurements to go though the whole range of suspension travel.  Then repeat with every combo of parts.

 

You really need accurate and smart measurement system to do this and plot it all for you digitally.

 

I ended up giving up after weeks and weeks of measuring. I established the bits I want to use and how they will optimise my setup and will do the final check on it when it is all assemebled.

 

76LXhatch, I did come up with a tweak to allow the top control arm pivot to be angled back without sacrificing camber gain and roll centre height.

 

Matt

[76lxhatch]

I wondered where yours ended up, saw the stuff you posted on Cardomain about extending control arms and the like but I don't recall seeing anything further. Would be very interested in how its going, and any tricks and tweaks you're willing to divulge along the way.

I don't have nearly the patience it would take to do everything manually, a few key measurements along with some maths and a spreadsheet is enough to do some fairly accurate modelling of suspension movement.

Anecdotally, I drove mine around 150km on Sunday through some reasonable roads and I'm definitely getting to the point where I'm happy with the improvements (for now!). In particular the understeer is all but gone and it is remarkably well balanced in corners these days (although swapping the Lokka for the Truetrac helped with that too).

[Bigfella237]

76LXhatch, I did come up with a tweak to allow the top control arm pivot to be angled back without sacrificing camber gain and roll centre height.

 

Matt

 

I was thinking more about that, can you get extended-shaft ball joints for a Torana?

 

If you could raise the upper ball joint centre by the same amount as you angled the UCA pivot it would give you some castor gain without sacrificing camber gain or RC.

[Bigfella237]

No luck finding extended length ball joints specifically made for Holdens but I've read on other forums that '70 model onward Chevrolet Camaro uses the same joints and you can get them in extended form from QA1 and AFCO that I've found so far...

 

 106200322LF_L.jpg   13.09K   3 downloads

 

I would've thought Moog would do them as well but I can't seem to search for cars that old on their website for some reason?

 

You can also get extended lower ball joints but I don't think you'd want them, extended lower joints would drop your ride height (same as a lowered spindle) but raise your roll centre.

 

BTW, while I was looking I saw this interesting concept and wondered if it would be legal over this side of the pond...

 

 3801990.jpg   15.48K   3 downloads

 

Simply substituting the threaded tubes for different length tubes would offer a world of possibilities!

[76lxhatch]

Ah yes tall ball joints are probably what Matt was talking about, I recall some comments on those now. The Holden ones do cross over so you would be able to get them bolt-in for the upper arms.

With that adjustable upper arm its a matter of clearance to the cross member. There was a thread somewhere here where someone tried a similar item and it didn't clear the cross member because with straight arms (rather than curved) the outer attachment points were too close together. Hopefully my description makes some sense...

[myss427]

I have purchased the 1/2 inch longer ball joints, mainly to cure the tall springs in the QA1 coilovers. Car is almost ready to drive, so will see what happens when it goes in for a wheel alignment.

[Toranamat69]

Bingo guys, it is the taller ball joints idea from the chev.  You were straight onto it.

[UC308Hatch]

Reading this with some interest. 67-69 camaro uca ball joints are the same as Torana.
Howe Racing do some that you might be interested
http://www.howeracin...fits-k5108.aspx

I'm using the +0.9" one on myTorana, but for a different reason (330mm brakes).



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[Toranamat69]

That's the ones I have too.

[Bigfella237]

Didnt Lenny (axistr) do the full steering geometry thing while he developed the power steering?

 

I'm sure I've read those p/s threads and Lenny was more focused on steering gear geometry, bump-steer in particular, which we've only really mentioned in passing here so far, but as we're moving control arm pivot points, that does need to be addressed as well.

 

If you draw a line through the UCA and LCA to body pivots, that line should also intersect the pivot points were the tie rods connect to the rack (in the straight ahead position) but if we angle the UCA pivots to achieve castor gain, I'm not exactly sure what we would now call the "pivot point" as the upper arm no longer travels in the same arc as the lower?

 

At the outer end of the tie rod, the tie rod end pivot should also intersect the line drawn between the upper and lower ball joint centres, but as we're also moving the BJ centres by extending the upper BJ shaft, I guess we need to either extend the shaft in the TRE as well or customise the shape of the steering arm to bring those three joint centres back into line?

 

But that only accounts for 2D (horizontal) geometry... we also have to look at the top-view, which is where the rack / tie rod centre-lines and Ackerman Angles / toe-out-on-turn comes into play, all of which are also affected by changing the arc in which the control arms swing!

 

Fun isn't it...

 

Reading this with some interest. 67-69 camaro uca ball joints are the same as Torana.
Howe Racing do some that you might be interested
http://www.howeracin...fits-k5108.aspx

I'm using the +0.9" one on myTorana, but for a different reason (330mm brakes).

 

You can't see from their single photo but those ball joints must be able to be disassembled by removing the top cap otherwise how would you changeover the different length studs they sell separately?

 

I assume that means you could shim the spring to set your own preload as well? Very interesting... I wonder how the cap attaches, is it secured by the same bolts that hold the joint to the UCA?

[UC308Hatch]

 
You can't see from their single photo but those ball joints must be able to be disassembled by removing the top cap otherwise how would you changeover the different length studs they sell separately?
 
I assume that means you could shim the spring to set your own preload as well? Very interesting... I wonder how the cap attaches, is it secured by the same bolts that hold the joint to the UCA?

Yes your on the money, the stud goes down into the body, then the cap screws into the body, set your clearance then lock the cap into position with the grub screws. The bolts only hold the body in place not the cap.

http://www.howeracin...tsPrecision.pdf

 ImageUploadedByTapatalk1425453065.928377.jpg   350.12K   9 downloads


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