Hi all
I would to know what ways people have sucessfully reduced turn in understeer.

My current set up is:
Front end - 120Y strut legs with Fulcrum coilover sleeves, 225lbs Kings coils, Koni yellow externally adjustable shock absorbers (set at the mid point but I have tried going slightly softer with no benefit), custom 17mm swaybar, strut brace, custom camber plates, urethane bushes throughout, 6 degrees negative camber and 5 degrees positive castor.

Rear end - LSD, Koni red shock absorbers (set on the softest setting), overider springs removed, 3" lowering blocks, Caltrac anti tramp kit (I have tried racing with and without the Caltrac bars fitted).

I am getting a lot of understeer at the turn in point. While some of this is due to the Falken semi slicks I am using having started to go hard I would like to optimise my suspension settings to reduce this issue.

I will be speaking to my suspension guy next week but I would like to know what experiences others have had in the meantime.

Thanks very much Matty

You've got all the good hardware in there and it's strange that you're having understeer problems. What is the body roll like? because 17mm is a pretty light swaybar.

The other thing is that camber and caster are supposed to help the turn in and reduce understeer but I'd suggest that 6 degrees is too much. It might be that case that you have so much camber that you aren't getting the car to roll enough onto the whole face of the tire. I would have thought more like 3-4 degrees of negative camber would be as far as you'd need to go.

seems the most straightforward solution is the add a rear sway bar

It`s a not a common thing to use a rear anti-roll bar in a 1200 in the rear and in my opinion is a bad thing unless your wanting oversteer for drifting , But if you use a rear bar use slightly softer rear springs. This will give you Less oversteer in the middle part of the corner, and it will give you more forward traction. Another thing that's being used a lot is front Roll Center Adjuster Blocks to make the Front a higher RC , if you have stiff springs, or heavy damping up front, the initial reaction when you enter a turn will be very strong. In the middle part of the corner the car will probably understeer, but it's the initial reaction that gives the car a 'responsive' character. Roll center works this way: a very high roll center in the front will make the car turn in very aggressively, but understeer in the middle of the corner. It's nice if you like an aggressive car you can 'throw' into the corners, but I doubt it's the fastest way round the track. Conversely, if the rear roll center is set very high, the car will turn in very gently, and possibly oversteer after that.But the rear Roll center is harder to adjust being a solid axle.
if you combined with your stiffer springs (and damping) up front, and softer ones in the rear with no anti roll bar in the rear . This makes for a very stable car: it will turn in sharply at first, because of the stiff springs up front, but then, it will understeer a little, because with the stiff springs and heavy damping up front, it takes some time to transfer the weight onto the outside front tire. This happens a lot faster in the rear. But eventually, when the weight is fully transferred, the car will steer very well. This setup can be very fast: the car can be 'thrown' into the corner, without losing a lot of speed because of the mild understeer. Then,just before the apex of the turn, some lite braking / liter throttle will probably be needed, but after that the car will be very stable again under power , like in the entrance of the turn, which makes a high exit speed possible.

Other things to look at are ..
Driver Braking to hard too late ,
Narrow front track
Front tyre Pressures to high
Too much front Anti roll bar

Your Front spring rate should be ok (depending on your Front roll center hight as mentioned above ) Not sure on the rear spring specs . I would have a look at your lower control arm angle and try some Roll center blocks if the arms are flat or pointing up wards to the strut end and don`t use any of the of the drag racing hook up tricks on the rear .

a rear bar on a circuit track or autox 1200 is pretty much a given here

i've always wondered how you fellas got along without them, and i now i understand

i think i'll try it your way next time, as i'd prefer my car to handle as you described

having said that, won't the handling dynamics of a ute differ significantly from the coupe?

Great analysis there Cameron.

I run basically a similar setup stated by Matty, with exception to front camber [I run ~3.75 neg degrees], front springs [275lbs] kings, 20mm front bar and increased track in front by 50mm.
I found that running the rear as soft as possible, the corner speeds have increased. I used to have a rear bar fitted [16mm] and the car would enter corner fantastic, mid corner was on edge and exit was oversteer city. Removed the rear bar and fitted softer reverse eye rear springs and the car was transformed.

I also run Falken semi slicks [RS-V04's] and only run around 24 - 26 psi.

As yet I haven't had any problems with understeer. I am toying around at the moment with having the H165 Diff housing Toe and Camber corrected.

cheers
benny

you can tie these cars down too much and I would suggest the removal or the rear bar. My race car does not run a rear bar at all but does run adjustable spax shocks.
You will find that your setup is quite good, but you will have to develop the technique to "loosen" the rear coming into corner entry and then 4 wheel drift the car through mid apex and then very slight understeer on exit.
This can be achieved with correct brake bias so at the critical point during straight line braking and the rear is unloaded, upon initial turn in, the rear will slightly break free during trail braking and then get on the gas at mid apex to keep the slide, but be careful not to get into oversteer.
The best racing drivers keep this balance during this critical point and thats where corner speed can be maintained and will slingshot you into the straight.
One indicator of this is that during the mid corner and onto the apex the steering wheel will straighten up even though the car is turning beautifully under throttle. Then when you come onto the straight as soon as point it in the right direction the car will just "hook up" and will feel like a slingshot.
This is the fastest way through a corner.
This is still something im still trying to achieve...and takes many years of having your bum in the seat.

oh further to this you will need some special springs in the rear. This is probably you biggest let down and these new springs will transform your car. PM me if you need details.

first thing I would say is turf the old hard semi slicks out and buy a new set. you might be chasing a problem that doesn't actually exist...

but agree with craig - sounds like your rear end could use a bit more attention. get rid of the lowering blocks and tramp bars and go see Fulcrum for a set of proper leaf springs - they've made a few sets to suit the power and torque of the CA18DET over the years.

Personally I like a rear sway bar - always ran one on my coupe. Certainly nothing wrong with a light rear bar to help tune the final balance of the car.

Some great answers!!

If the front end is the problem, isn't it preferable to work on that end of the car??

eg if car understeers it means that front of car has enough traction to travel at say 50 km/hr around a bend whereas the rear of car has enough traction to travel around the bend at 60 km/hr...

by playing around with the rear....the car may become neutral....but only beacuse you decrease rear traction capabality to 50 km/hr....

if you play around with front end...and manage to improve the front end traction cabalities so that the front can go around at 60 km/hr....then you also end up with a neutral car...

the diff is one car is neutral at 50 km/hr...the other at 60 km/hr!!!

Interesting points - good for mulling over.
My reading of late has me looking at the rear end of my car to assist the front - sounds strange but aparrently true. I have a picture at my last OP supersprint which shows it perfectly. Leaf sprung live axles have roll understeer built in by the manufacturer and fortunately there is a simple cure - I'm hoping so anyway!! My car is suffering from a bit of diagonal transfer with an outside rear taking too much load and unloading the opposite side front - so what can appear a front suspension issue can be actually a small problem being magnified by another - in this case, the rear. Suspension is rarely a black and white science so read up and ask questions because everyone has a theory
I agree that 6 deg neg is a little steep - 4 to 4.5 would be max I have been told.
Driving style is another indicator as pointed out earlier - and if you have a locked diff. If you do have a locker, you will either be braking, on the gas, or understeering - go or stop - if you don't DRIVE through corners with a locked diff the diff will tend to drive you
Hope this thread continues - will be a good learning tool for everyone.
Cheers