RA23 Loves to oversteer!

[damian]

I do actually want to do some track days but the way the car is at the moment it is unpredictable and dangerous. I'm picturing big clouds of smoke at every corner.

this is what a track day is for so you can find what to do to make it safer and more predictable, without risking hitting parked cars, gutters, poles, kids...
spend they day trying different setups, removing sway bars, etc

[Cuzzo]

Those tyres look like trailer tyres....Get some better / sticker ones.

[damian]

^^ agreed 10ch

[timbosaurus]

Ignoring the fact the you've got a powerful car on shitty rubber and a heavy foot.

Ignoring any possibility that car control could do with some improvements.

It sounds like your car could be suffering from rear roll oversteer. This makes it a pig to control as soon as you start to put a bit of ooomph into it.

Big contributing factor could be worn trailing arm bushes, so check there is nothing wrong there. Stuffed rear bearings wouldn't help either... but it they were bad enough to cause rear rollsteer you'd hear about it.

Also, if you're ride height is different left to right, it could cause dramas. If your diff is not centered after you've lowered it, the same will happen. Both of these wont cause it to the extend you are describing, but could if combine with a binary foot and sluggish hands.

Have a search on the web about rear rollsteer, and if, after that, you still need an explanation as to why is causes such huge stability/control problems, let me know.

Cheers,
Timbo.

[SilverRA23]

You don't need to remove your rear sway bar to determine if its the problem

Simply disconnect one end of it, so that its not longer transferring the force from one side to the other. then take it for a run and see how it goes.

One Celica I know was lifting a rear wheel because of the stiffness of the rear bar, and when you lift one wheel you reduce your grip by 50% immediately.. resulting in violent oversteer.

[jabbatron]

..........

[MWP]

... when you lift one wheel you reduce your grip by 50% immediately.. resulting in violent oversteer.

No you dont... no where near.
Most of the weight/grip is on the outside tyre mid corner, and the inside isnt contributing much grip at all.
Lifting a tyre is bad, but sometimes its cant be avoided to gain other better suspension qualities.

[damian]

correct that will not reduce grip by 50%, but it will increase the amount of weight on the remaining 3 wheels (the car weighs x kg, and no matter what, that weight has to be supported by the wheels in contact with the ground), and if the tyres remaining in contact with the ground are already at the limits of grip, then lateral force (which hasn't changed) will be more than the grip levels of those remaining tyres, and those tyres will slide.

of course while transferring the weight from that inside wheel to the other 3, it also increases the grip levels of those tyres simply because there is more weight on them, but it's a balancing act and a black art

the inside wheels surprisingly do contribute a fair amount towards grip levels. One thing driving instructers will teach you about is the above scenario

[damian]

...Simply disconnect one end of it (swaybar), so that its not longer transferring the force from one side to the other. then take it for a run and see how it goes..

i would strongly suggest disconnect both sides, not just one, otherwise one side will still be linked up to the car and may make it behave very unpredictably.

Myself, I would spend the extra 3 (or 10 if the bolts are a bitch) minutes removing the whole thing.

also, further to grip and weight transfer

For a given size of tyre contact patch, the amount of cornering force it can generate depends on the vertical load (or weight on the tyre) and the co-efficient of friction (ie "sticky" tyres are better). As we increase the load on the tyre, it turns out that the the relationship between vertical load and force that can be applied before slippage occurs is not linear. This is because the co-efficient changes with the vertical load applied. In particular, if you apply twice the load to the tyre, you do not get twice the cornering force.

more here which i think i found here, but a quick bit of googling will find you similar stuff around
I had a better page that explained it a bit more in easier language to understand, but lost it when my last pc crashed and lost all my bookmarks

[timbosaurus]

Mwp, I agree that with full weight transfer, on the verge of jacking a wheel, it won't make a difference. But he's talking about turning a corner at 20kph, were u'll have (next to) no weight transfer at all.

I still suggest there is something in your setup, either because ur rear is higher than the front, the axle is offset, or one spring is soft, or trailing arm bushes are worn, causing roll oversteer.

This is when you turn left, the rear turns slightly right and all of a sudden ur 5deg steering input means makes 6deg of yaw... making the rollsteer worse, making 7deg of yaw, making rollsteer worse, making yaw worse etc etc etc... ending in spin... game over.

[damian]

grip vs load is not linear, so jacking a wheel in the air does make a difference, and can result in loss of grip on the remaining wheels.

example - taking a tarmac corner on the limits of grip, throw (prob not a good choice or word) the inside wheels onto the gravel (therefore less grip on inside tyres as traction is reduced) and they start sliding, which transfers more weight onto the outside tyres, which if already at the limits of grip, also start sliding.
same effect as lifting a wheel in the air.

but yes, at 20kph there isn't (or shouldn't be) enough weight transfer to make it suddenly and violently break lose.

Timbo's suggestions of suspension problems are almost certaintly spot on. Makes perfect sense.
Sounds like a bit of work for ya Jabbatron

new tyres ftw too

[sleeektoy]

From my track experience with the same problem, The biggest change i found was by lowering the rear(or raising front) to be lower ride height at the back.
Im not sure but i guess the weight transfer mid corner back to front is less but it made a massive difference with the rear lower.
Much happier to give it a bootfull mid corner and know it will be controllable.
Also removing rear swaybar should help as well.

[smiley_666]

not sure if it'll help, but with some cars (ford escorts in particular) a rear sway bay can cause overstear. From the experiances of these cars, completely removing the rear sway bar removed the excessive overstear.
may be different with the RA23, but it may be a place to start

[andrew_mx83]

an oversteering problem.

no such thing.

1. countersteer
2. throttle
3. ???
4. profit


seriously though, a swaybar will give the illusion of more grip at the opposite end of the car, whereas its really reducing grip on the wheels it is connected to.
ie more rear swaybar = less rear grip = oversteer
more front swaybar = less front grip = understeer

unbolt the rear bar from the control arms and take it for a spin. however it sounds like you may have more suspension issues (as mentioned above) than just too much swaybar.

[JustenGT8]

Take it to a suspension shop and get the whole lot checked out. It doesn't sound like there's anything fundamentally wrong with the make up of your setup and looking at the rear bar, i ran at least that thick on my 23 (18mm from memory?). It sounds like something is worn or out of alignment and causing the ugly weight transfer.

Your tyres are definitely shite.