Suspension Geometry and lowering

[gareth12]

Considering lowering the sigma (gj wagon, v8) by 30mm but i have read a few times on this forum that it puts the suspension geometry way out. My reason for lowering is handling not looks so i was wondering if this might be counter productive.

Any thoughts?

[gareth12]

would love some input on this?

[Billsy]

they never had great geometry anyway.

lowering them though will make them handle much better. the stock center of gravity sucks so the lower you get it the better,

add more castor and camber and youll easily end up with more front grip than rear when turning in. but likely also get some understeer under power in certain circumstances like most cars.
The steering angles are crap and change from side to side as you turn lock to lock. making a terrible (rear end spins 180 VERY easily as steering geometry binds up the front wheels as you near lock) drift car

all depending on what the rest of your cars setup is regarding swaybars, wheel and tyre sizes etc.

[ddt]

i'm pretty sure that you get the least body roll when your centre of gravity is the same as your centre of roll.
Cars like the Toyota FT86 are designed so that the centre of gravity and roll are both low -that means they can run relatively soft suspension. The result is something that handles well and is still comfortable.

If you lower the front of your sigma 30mm, you might lower the centre of gravity by 15mm or so but you will almost certainly be lowering the centre of roll by more than 15mm. This will result in more body roll. The lower you go the stiffer the springs you will need to reduce roll. However because the rear is live axle i *think* lowering the back would probably raise the centre of roll, while lowering the centre of gravity -which is good! With a V8 in the front of your wagon i'm not sure if lowering alone would result in a net gain in handling. I vaguely remember Cheaterparts posting before about suspension setups- i think his sigma is pretty low but has front sway bar and tons of camber etc..

My sigma wagon has been lowered 50mm and it handles fine for me (king springs in the front and reset standard height Pedders in the rear) but it's just a cruiser.

[Sigmaproject]

Go the WAGONS...

I lowered mine at least 60mm at the front (lowered lovells + half a coil in shortened Starion struts) With pepperpots and 55 series Bridestones
Back is 30mm lower with 30mm hub spacers and 60 series Bridgestones. It handles like it is on rails. Hard suspension is not so good for the crappy country roads around my area.
I am actually thinking of raising the front a little. Putting in some springs that are a bit softer. Straight line stability is not one of its strengths, unfortunately.

[gareth12]

thanks guys, i will probably try 30mm all around and see how she goes

[jiff]

Am i the only one whos raised the rear

[gareth12]

heh, my the time i get a 225/60 15 or 245/60 15 in there mine will be a fair whack higher.... I have checked ground clearances and such, think i will leave it stock height, its a bit lower at the front because of the heavier engine, if anything ill get some kings stock height and go from there, but will try a set of the new monroe shocks first and see how that pans out

[BAD-SIG]

I've been playing with the suspension on Sigmas for years to suit street cars. I currently have the best combo on my golden GE sedan. You want to lower the car until the front lower control arms are straight with the crossmember (King low springs achieve this) and fit a thick Whiteline front anti-roll bar. Also fit King low springs to the rear but do NOT fit a rear anti-say bar because that will dramatically accentuate the understeer. I found the car has a perfect balance with this setup together with 195 wide tyres on the front and 225 on the back.

[Dion383stroker]

Where can we get Whiteline sway bar? Hard to source suit GK

[Sigmaproject]

I had a rear one made for a wagon about 10 years ago. I got in touch with them a couple of years back with regards to a fitting kit...and they told me that Sigma bars were no longer in the system.

[BAD-SIG]

I bought my Whiteline front and rear bars off a guy over 10 years ago who used to race a GH Sigma on club circuit races, no idea who he was, just found him on Ebay...

[JBSTAZ]

Bad Sig I would have thought that fitting a heavier front bar would increase understeer and adding a rear bar would help reduce it ??? as that is the exact opposite to any handling specs I have seen to date.

[JBSTAZ]

Info to read re handling mods http://www.k-mac.com/pages/tuning/tunin ... ghints.htm

[BAD-SIG]

Imagine you are going around a right hand corner for example and you have a heavy front sway bar but none on the rear. The front will have very little sway but the rear will have heaps and will want to overtake the front, hence oversteer.

[cheaterparts]

Imagine you are going around a right hand corner for example and you have a heavy front sway bar but none on the rear. The front will have very little sway but the rear will have heaps and will want to overtake the front, hence oversteer.

No mate if you stiffen up the back with a sway bar you will create oversteer not reduce it

My track sigma probably ran around corners a little quicker that any road version and still had to use most of the std bits being an IPRA spec car
it was easier to get the front to hook up in a corner than the rear

the car was lowered so the cross member was just above the min height ( 100 mm ) I used a heavier front bar than stock 300 lb springs , plenty of camber 3.5 - 4 deg and caster 5.5 - 6 deg and depending on the track the amount of toe out
this F/E turned in well and created very little push

The read end was a different matter - early on I used After market bushes that were stiff and that made the rear end bind I had a small sway bar and not sure how heavy the springs were
in time the swap bar was scraped - the bushes in both top arms went back to std rubber , the inner links that go from the lower links toward the diff were removed
and some lighter rear springs fitted ( sorry cant remember there weight )

by then the balance was becoming quite good - my findings with the sigma rear end is the std links make the rear axle bind up and doesn't let the axle work properly
making the rear end stiffer just makes them slide
and trust me when you are in turn one at Phillip Island a bit over the ton the last thing you need is the back beating the front -