197 replies to this topic

[Toranamat69]

Milco, Get some UC steering arms, they are better for a std UC setup.

I can show you the difference graphically if you like of what it will do to your bumpsteer curve.

M@

[hatchssv8]

M@,

Is the following front end make up what you refer to as being the best Torana set up-
1. UC upper control arms ( unique across the range with the offset balljoint)
2. Any lower control arm ( the manuals do list a few but non of the differences affect the suspension geometry)
3. LH/X UC stub axles (both drum or disc, retaining the 9 degrees KPI)
4. UC steering arms (longer and with slight angle difference at tie rod end)
5. LH/X UC xmember (esuring the holes are in the LX RTS position - Lowermost accross the range)

A few questions I have -
1. Is this set up for a particular ride height and tyre width?
2. Is this for street use (biased towards handling rather than comfort)?
3. Is there any further requirements for your ideal set-up? ie spring height min/max.

You dont do things by halves, so what you add to this discussion is not taken with a grain of salt. If there is any way I can assist with your investigations/experiments, just ask.

Lastly, can I ask why your set up would be the ideal set up as you describe.

Thanks, Max

[Toranavista]

Hi Matt, Is it possible for you to post a reverse shot of the hole in the crossmember. ie from the wheel side.

[Toranamat69]

I'll do the easy answers first.

Toranavista,

Here is the pic from the other side.



I must have read your mind, I already took this last night.

M@

[Toranamat69]

Milco,

Here is the bumpsteer curves for the UC Torana Front end set up as close as I could to standard ride height, using all 3 options of steering arms.i.e. UC, LH and A9X. This front end was setup with 2.6 degrees positive castor (I thought this was a good maximum setting for a Torana with manual steering) as this has an effect on these curves.



The perfect bumpsteer curve is a vertical line. Notice the light blue (UC one) is the closest to ideal. The curves would be closer to vertical except I have stretched the horizontal scale out to exaggerate the difference.

The LH steering arm gives pretty much 2 times the bumpsteer that the UC one does on that setup.

These curves should actually be nice smooth curves, the little wriggles you can see (especially in the purple curve around the zero mark) are the errors in the 4 or 5 measurements that are required for each point on the curve.

As far as I know you do not have dramas getting the correct suspension settings for street use in the UC when you drill the UCA down low. The problem on UC toranas is the other way, you run out of shims to remove when using the 7 degree stub axles and still have lots of negative camber.

M@

[Toranamat69]

G'day Max, I am really glad to get some good discussion going on this topic as I continue to learn heaps the more I look into these things.

I assume you have checked out page 2 of my cardomain site as to where I am upto on my front end project as it is a work progress. I do plan to see what I can modify to make further improvements but most of these will require Power steering to be take advantage of the modifications.

I'll try to comment/answer your Questions best I can below but some of them do not have a clear yes no answer, they depend on the rest of your setup.

1. Yep UC arms are my choice of the available ones.

2. Yep all the LCA's have the same geometry.

3. The 2 differences between the 7 degree and the 9 degree stub axles are a) the scrub radius and b ) when you turn, the 9 degree stub will lose more negative camber.
This is a fairly small amount and 1/4 degree more positive castor in your static setting will pretty much cancel this effect of b )
The scrub radius thing is more relevant. The scrub radius depends on your wheel/hub offset, KPI and wheel overall diameter. I have to draw up a diagram in CAD to work out what the best setup is depending on wheel sizes.
I will do this for a series of different wheel diameters and for both stub axles - that is the best way to capture it.
You ideally want zero scrub radius. I am going to use CRS 2" drop HR stubs in my new setup. These are 7 degree KPI and 2"drop from Torana height.

4. UC arms for std UC setup, A9X arms for the HQ stubs. The 'effective length' of the LX and UC steering arms is very similar, the difference in length is to drop the outter tierod vertically.

Answers to your questions.

1. All of my measurements I have done so far, I have tried to simulate the original Torana setups on standard sized wheels - I then adjust these as I require for mine with my larger front wheels on it.

The Roll centre measurements I have done on my cardmain site use my current front wheels (255/40-17's) as that is what I needed to know in that exercise.
I am getting better on cad so they are easy to modify to check other combos anyway.

2. If my current plans work, they will work superbly for street or track with the appropriate different spring and shock rates. Getting a better camber curve whilst not killing the roll centre should improve the Torana handling.

The way this theory works, if you start with -1.5 degrees negative camber (lots for the street so you wear the inside edge) and a fairly stiff suspension then as you corner hard(ignoring castor and KPI effect here) your car may roll say 4 degrees to one side.
Now you might think the wheel has now rolled over and off the road by 2.5 degrees but if the suspension has now compressed by 25mm on that side, you have gained another .15 degree negative camber so that wheel is actually cambered to the road at 2.35 dgrees positive. -not good but the reality and wearing the outside edge.

Now if you imagine the same scenario with the control arm drilled 1" lower, looking at my other measurements I have taken, you would now gain approx 0.6 degrees more negative camber(not measured) so the wheel is only now rolled over at 1.9 degrees positive camber. Slightly better but could go more.

The softer your springs, the more important a good camber curve is as you car will roll a few more degrees on a fast corner to say 6 or 7 degrees. Ideally the tire should be planted on the ground at zero degrees or slight negative camber to bite into the road, if you do this with a camber curve rather than static camber, your car progressively bites into the road as you go faster and runs less static camber so at all times the tire should be closer to flat on the ground.
Not only does this make the car bite into the corners, it make your tires wear nicer.
The front tire wear on Toranas usually confirms this scenario. This applies no matter what wheel and tire size you run.

3. I would stay within 1"of standard height for springs and if you want to go lower than that, do it via a stub axle change. if you lower more than 1"in the spring you are getting a bit close to the bumpstop and you are sending the front roll centre underground.
I am pretty much running what I view the optimum setup of original torana bits in my LX now and I am not happy with it at all which is why I am undertaking this big task but alas I think what you numbered 1 to 4 above is pretty much the best you get using combinations of the factory parts. Hard to choose between the HQ or Torana stub axles - depends on the wheel offset and diameter.

M@

Edited by Toranamat69, 27 October 2006 - 06:09 PM.

[hatchssv8]

Matt,
Thanks for the feedback, answers and your theory. As you can deduct from my pics, I have cleaned, painted many suspension bits, all ready to be assembled.
I also have prepared HQ stubs, LX UCAs, LX xmembers....you name it.

I will start off 21/60/15s and possibly move to a 17 in the future. Following what you have done, I was thinking of drilling the lower holes for the UCAs prior to assembly, then I would be able to utilise those if required at a later date without the task of tearing the front end down completely etc.

I think I will go away and make a check list of what needs to be prepped for the above scenario.

Again, if I can help in any way, just ask. And will follow your progress.

Cheers, Max

[hatchssv8]

Keith,
UCA - Upper control arm or Upper wishbone
LCA - Lower control arm or Lower wishbone



I think M@ is running the set up you prpose in your post. ie using the lower UCA mountings on a UC front end. Lets wait to see if he can comment on adv and/or disadv.

Max

[TerrA LX]

what UCA is the best to run with the A9X type steering arm and HQ type stub running 600mmod tyre.

[fuzzypumper]

Hi,
Ive had a UC RTS subframe with nolathane bushes on my LX V8 hatch for at least 15 years running 13"x7 wide steels rims with 205/60 tyres and heavy duty springs lowered approx 1" basically making the steering arms horinzontal (tierod to tierod straight inline with rack when viewed from front).

It always annoyed me that I'm changing front tyres early because of wearing the outer edge. I recently put new front tyres and now kringe every time I turn the wheel and here that rubber peeling off. The reason I put in the UC front end was to get the better RTS and better tyre wear so this thread is of great interest and slight confusion.

My intention is to keep the UC setup and by the testing done in this thread it seems i would be better off drilling lower holes in the tower for the UCA. Is that right? If so what wheel alignment settings should I use?

I've always driven out of wheel alignment centres wondering whether they listened to me when I said "It has a UC torana front end not a LX torana front end so wheel align it accordingly"

Also UC had a more negative caster due to offset UCA balljoint position but because of this making steering heavier(and lack of return to centre),they had different ratio sterering rack I believe or didnt they? Please correct me if my geometry or info is wrong?

Edited by fuzzypumper, 31 December 2006 - 10:21 AM.

[Toranamat69]

Keith, redrilling the holes for your upper control arms in the lower spot will only have a very small effect on your bumpsteer curve.
In my experience, it will improve your front tire wear. The Torana front ends love wearing both the inside and outside edges way before the rest of the tread.
This does seem to improve things. A bit more adjustment would be good too.

ALX76, If you have LX arms there, just use them, if you have none yet, I would hunt down some UC ones. You can get all usable street camber and castor settings from both LX and UC arms but you will end up with more even shim packs if you use the UC which is good as they are not as prone to fall out. You can run more overall positive cator with UC arms but in my experience with my car, any more than 2.8 degrees positive castor is heavy to steer.


M@

[Toranamat69]

Fuzzypumper,

Apart from wheel size, it sounds like your setup is very similar to my current setup in my car, and yes I have my UCA in the lower spot.

My first set of tires didn't wear perfectly, I wore through the inner edge with about 15% tread left on the rest of the tire. I was running 1.5 degrees negative camber and 3.0 degrees positive castor.

Since I have changed tires, I set the front end up with approx 0.6 to 0.7 negative camber (slightly more 1 side) and 2.8 positive castor.

I have done about 12,000 km's on the new tires and they are looking pretty good.
A tiny bit scuffed on the inside and outside but not like you see on most Toranas (and remeber I am running 255's up front so they exaggerate the problem)
This is why I think a tiny bit more aggressive camber curve and/or more positive castor would be good to really sort the tire wear out.

The UC's ran more positive castor which gives you more self centreing of the steering and did have a different steering ratio but I am not sure if they achived this in the rack or the steering arm length as I have never checked, I suspect it is the steering arm that makes the difference though.

I hear you about lack of confidence in alignment shops, I am still looking for a good one. Some of the better ones give you a printout of your settings but then again, I have had one of these better ones break my brand new steering wheel horn button and forget to reinstall the steering wheel locknut and my steering wheel loosened off (this seems standard practice actually)

M@

Edited by Toranamat69, 31 December 2006 - 07:20 PM.

[fuzzypumper]

Thanks Toranamat69 for the advice and Happy new year.

Now for the Rust!

[Toranamat69]

Devils, I was just concerned they broke stuff and didn't refit the lock nut.
This was the first wheel alignment from when I put the new front end in so I had just lined everything up by eye - it didnt surprise me they had to take the steering wheel off and jump it over a tooth.

From memory you don't have a lot of adjustment on the tie rods so it pretty much has to be on the correct spline on the steering wheel.

M@

[REDA9X]

Some interesting reading here. A few points I picked up on though.
All LH and LX top arms are the same, and can be swapped from side to side. Basically SFA changed when LX went to RTS, it was all spring rates, shocks and tyres. Most of these things would have been improvedby owners over the years on PRE RTS cars anyway. Only the A9X and UC arms are any different and A9X are slightly different to UC.
Bottom arms are unchanged across the range except for the steering arm bump plate posiioning.
Yes the seering rack in an A9X is solidly mouted, but no the crossmember is not solidly mounted to the chassis, ouch!!!!
The A9X top arms were not mounted in the lower mounting holes on road cars, race cars may have used them depending on their track requirements on the day.

[REDA9X]

Just means someone moved them. Mine came with a chrome aircleaner too......

[A9X]

might not be an a9x ?

Best you get rim's mate to check it out for you.

[Toranamat69]

A9X, good one mate

REDA9X, that's very interresting the A9X's were in the top holes, I have checked a few at shows and they were all in the bottom hole. Trivial point probably but I should change my cardomain site when I update it as I think I do mention it a few times in there.
This was a common mod so it doesn't surprise me people have changed it at some stage.

M@