Strange transitioning understeer problem

[Steve]

Hi all,

I have been playing with my sus a bit of late, and still seem to have a nagging problem with understeer at medium and high speeds.

going through a corner, maintaining speed I get understeer. If, into the corner I accellerate, the understeer disappears, rather suddenly, causing me to go too deep into the corner - its a bit frustrating, and a bit dangerous as the transition is very quick, not always allowing enough time to adjust properly - havent come unstuck yet thank god.

I have changed my front camber arms, running approx 2deg camber, castor is around 9degrees. I have whiteline swaybars adjusted to full tension, pineapples and hardmounts on the rear cradle, 1/2cage, and ohlins adjustables with 8kg springs front and softish (perhaps 3kg, unsure exactly) springs in the rear. I use damping to counter the soft springs in the rear, and hope to update these soon, I will be fitting a hicas lock bar and wheel spacers soon too. Ride height is 345mm center of wheel to guard.

Does anybody have any ideas what can be causing this understeer problem? Anybody have similar dramas?

My first thought is its the bloody hicas doing its thing?

Cheers

Steve

[EnricoPalazzo]

what tyres steve?

[EnricoPalazzo]

also it could be hicas, however usualy hicas is a rear steering problem not front....??

[Steve]

I have goodyear revspec front and RE540s rear.

Although the hicas is on the rear, it effects steering too - I am pretty sure it is the HICAS, but was interested to know if anybody had this problem and found it was caused by anything else.

Its sort of strange, but the more handling mods I do, the worse it gets, with the last being the roll cage, its just really p1ssing me off now.

[Steve]

Actually come to think of it, the more handling mods, the harder I can push the car, so the more pronounced the problem....

[EnricoPalazzo]

yeh well that makes sense what u r sayin in that the harder u push the worse the problem. However my experience with the hicas is that when i chose a line thru a corner, mid way thru it the hicas kinda turns in more giving me an oversteering problem, nothing to do with understeer. Does that make sense?

So yeh maybe ur front suss is set too low, this used to give me cronic understeer.

[fatz]

you have gun tyres on the rear and not so "gun"tyre on the front

there is your understear- the rears are to good for traction thus the fronts cant keep up

re540 renounds for being great till they finally do go then its hold on

same tyre front to rear would make a world of diffrence

[Duncan]

my vote's with pete's answer, try r tyres on the front as well. you may simply be running out of mehanical grip.

?

[Steve]

I thought it may be the grip of the front tyres, but why then do the tyres grip when the car accelerates? wouldnt the weight transition to the rear of the car cause more understeer?

Or is it a case of the change in inertia allowing the tyres to bite better? Either way, I would like to get some R rubber on the front, and something a little less grippy on the rear.

I had a similar problem when I was running revspecs all round.

Anyone got some legal second hand 235/45/17 R tyres they want to get rid of?

[mist]

run your front whiteline swaybars softer than the rears. a bit more roll, but less understeer.. tradeoff works for me for now. would love to buy a new set of thicker bars front and back tho.

mis-matched tyre combo - try the revspec @ the rears, drift around instead of under hahah

[Duncan]

I thought it may be the grip of the front tyres, but why then do the tyres grip when the car accelerates?  wouldnt the weight transition to the rear of the car cause more understeer?

Or is it a case of the change in inertia allowing the tyres to bite better?   Either way, I would like to get some R rubber on the front, and something a little less grippy on the rear.

I had a similar problem when I was running revspecs all round.

Anyone got some legal second hand 235/45/17 R tyres they want to get rid of?

funny you should ask, I do have some tyres in that size that I want to get rid of, its a long way to ship from Sydney tho http://www.skylinesaustralia.com/forums/sh...ead.php?t=39170

[Steve]

Nice job on the RE55s, how do you rate them?

and how much for the DJ01s (235/45/17)? I can probably organise freight from here if the price makes it worth while, please pm me:)

[Clint32]

you will have more grip when you are acceleating, you brake turn and slowly apply power to push you through the corner, you will always understeer when pushing if you are not driving the car, ie on the gas.

but yes the tyres need to be the same coumpond front to rear to get the best, and dont think of the front and rear, they both affect each other, too much grip on the rear and you will understeer, to much on the front and over steer, simple, its all about balance

[GTR32]

Hi all,

I have been playing with my sus a bit of late, and still seem to have a nagging problem with understeer at medium and high speeds.

going through a corner, maintaining speed I get understeer.  If, into the corner I accellerate, the understeer disappears, rather suddenly, causing me to go too deep into the corner - its a bit frustrating, and a bit dangerous as the transition is very quick, not always allowing enough time to adjust properly - havent come unstuck yet thank god.

I have changed my front camber arms, running approx 2deg camber, castor is around 9degrees.  I have whiteline swaybars adjusted to full tension, pineapples and hardmounts on the rear cradle, 1/2cage, and ohlins adjustables with 8kg springs front and softish (perhaps 3kg, unsure exactly) springs in the rear.  I use damping to counter the soft springs in the rear, and hope to update these soon, I will be fitting a hicas lock bar and wheel spacers soon too.  Ride height is 345mm center of wheel to guard.

Does anybody have any ideas what can be causing this understeer problem?  Anybody have similar dramas?

My first thought is its the bloody hicas doing its thing?

Cheers

Steve

Steve;

Does the car actually transition to oversteer, or does it just seem that way because it stops understeering.

Is the car lowered? Is it possible you're experiencing coil bind?

I agree your sway bars are probably adjusted incorrectly, as previousy suggested. Try going softer on the front.

[Genesis®]

i posted this up a while ago. Hope it helps

http://www.skylinesaustralia.com/forums/sh...hlight=sway+bar

[Steve]

Thanks for all the input guys - spose its time to adjust my front sway bar.

GenisisR32, nice article, makes sense now - the harder the front sway bar, the more weight comes off the inside front wheel - which also ties in with accellerating bring the weight back onto the front inside wheel, thus the sudden bite.

Only one problem, I still have a little more body roll than I would like, will backing off the front increase the body roll dramatically?

The article Genisis R32 posted the link to suggests a tighter rear sway bar will have the same effect as loosening the front - does anyone make heavier sway bars for the rear than the whiteline adjustable??

Thanks again

Steve

Edit, my ultimate aim is to be able to push the car a bit harder. I am thinking I might just have to buy some wheel spacers and see how much they help, cos I dont want any more body roll than I have, if anything I want less. Also, transferring the weight back to the front inside tyre will result in weight coming off a drive tyre, which means more prone to oversteer...... ah, to find the perfect solution:(

the merits of the japanese tendancy to dump the car and fit hard springs and wheel spacers (or wheels with crazy offsets) is really starting to look good to me.

[GTR32]

Thanks for all the input guys - spose its time to adjust my front sway bar.

GenisisR32, nice article, makes sense now - the harder the front sway bar, the more weight comes off the inside front wheel - which also ties in with accellerating bring the weight back onto the front inside wheel, thus the sudden bite.

Only one problem, I still have a little more body roll than I would like, will backing off the front increase the body roll dramatically?

The article Genisis R32 posted the link to suggests a tighter rear sway bar will have the same effect as loosening the front - does anyone make heavier sway bars for the rear than the whiteline adjustable??

Thanks again

Steve

Edit, my ultimate aim is to be able to push the car a bit harder. I am thinking I might just have to buy some wheel spacers and see how much they help, cos I dont want any more body roll than I have, if anything I want less.  Also, transferring the weight back to the front inside tyre will result in weight coming off a drive tyre, which means more prone to oversteer......  ah, to find the perfect solution:(  

the merits of the japanese tendancy to dump the car and fit hard springs and wheel spacers (or wheels with crazy offsets) is really starting to look good to me.

Steve;

I'd like to suggest some caution here before you decide on anything. Not trying to state the obvious but the 'Japanese' approach might make your car drive, ride and handle like a Woolies trolley. Don't forget that they are chasing a 'look' also. Suspension can be like the mythological 7 Headed Hydra - cut off one head (ie problem) and two grow back. Given the integrated manner in which suspension has to work to perform it's role well, unless you really know what you are doing and can balance the whole thing properly - suspension is a black art, very few people can really do this well - you can spend lots of time and money and end up with a car that handles terribly. Even some commercially available 'packages' aren't as good as they should be.

It's only by knowing where you are currently, where you want to go and how to get there that you can plan an approach and know it's for the right reasons, with money well spent.

I did lots of research, found some people I trusted, had my suspension rebushed etc as required, got springs and shocks dynoed and found that I had to get new springs because the existing ones were were binding. Dangerous. New springs were designed specifically for my intended purpose, cost me about $300 to get the dyno and design work done. However, now I actually know what's there, what it can do and why. Money well spent.

Not trying to tell you to suck eggs, just hate seeing people waste money.

Can I ask why you want less body roll? Cutting out body roll all together, unless you're on slicks, can be problematic as far as I know.

Cheers,

Mark

[Steve]

Mark, I agree totally about the whole black art thing - its takes alot of work, and one thing that gives great results in one car, may not work for another.

I have driven in a couple of cars set up jap style, slammed, widened, heaps of castor and camber, hard springs - and I liked it. The cars handle like go-karts, I liked it alot. I prefer a bit of oversteer than understeer - which is what I have at the moment. I find oversteer with a mechanical diff (which I have) quite easy to control. Having said that, I dont want a tail happy car either - but I dont own a MR2;)

I want less body roll because I have too much for my liking - I dont want a car that wallows around - when I push my car, it feels to me (passengers have stated otherwise) that my car bodyrolls a bit too much.

I also realise that going too hard on springs can cause more trouble than it cures - but I am definately not there yet. I dont want a car that will bounce me off the road if I hit a bump.

I dont want to completely remove body roll - but I definately have more than suits my driving style, and currently its too much. I have asked a mate that I know can drive very well to take it for a spin to see what he thinks - he came up with the same problems I did, lazy turn in, too much understeer, too much body roll.

I appreciate your words of caution, but at the end of the day, it sometimes takes trial and error to get it 'just right'.

If you have any hints, things you have tried that helped, please do share - as I am open to suggestions:) Bottom line is, until you try for yourself, it can be hard to say when it comes to fine tuning a car's sus - what one person loves, another may hate.

Cheers

Steve

[GTR32]

Mark, I agree totally about the whole black art thing - its takes alot of work, and one thing that gives great results in one car, may not work for another.

I have driven in a couple of cars set up jap style, slammed, widened, heaps of castor and camber, hard springs - and I liked it.  The cars handle like go-karts, I liked it alot.  I prefer a bit of oversteer than understeer - which is what I have at the moment.  I find oversteer with a mechanical diff (which I have) quite easy to control.  Having said that, I dont want a tail happy car either - but I dont own a MR2;)

I want less body roll because I have too much for my liking - I dont want a car that wallows around - when I push my car, it feels to me (passengers have stated otherwise) that my car bodyrolls a bit too much.    

I also realise that going too hard on springs can cause more trouble than it cures - but I am definately not there yet.  I dont want a car that will bounce me off the road if I hit a bump.  

I dont want to completely remove body roll - but I definately have more than suits my driving style, and currently its too much.  I have asked a mate that I know can drive very well to take it for a spin to see what he thinks - he came up with the same problems I did, lazy turn in, too much understeer, too much body roll.

I appreciate your words of caution, but at the end of the day, it sometimes takes trial and error to get it 'just right'.

If you have any hints, things you have tried that helped, please do share - as I am open to suggestions:)  Bottom line is, until you try for yourself, it can be hard to say when it comes to fine tuning a car's sus - what one person loves, another may hate.

Cheers

Steve

Steve;

I had Ohlins hard mount shocks and springs. They were way too hard and I got some standard units as a baseline so I could drive the car while I had the Ohlins set up dynoed - you know the rest. I sourced adjustable castor and camber bushes and pineapples from Whiteline, which made the car feel much better. That's all I did other than get a good alignment. The same approach worked for two other cars, both of which have good suspension given their design limitations.

Unfortunately all set ups are a compromise, as you know. We ran radical camber angles on an AUSCAR but when we came off an oval circuit the whole thing had to be changed dramatically. If you want to get rid of body roll by all means go down that route, but if you eliminate body roll you might ask what trade offs you'll have to accept.

[ADM]

Steve,

8k front springs on a road car with road rubber are too hard. As soon as the spring stops compressing and the mechanical grip of the tyre is exhausted the tyre will slip. So a massive spring rate at the front will cause the front to slip before the rear creating your understeer issue. The idea is not to stop the car rolling altogether but to ballance the amount of roll front to rear in relation to the rubber and tarmac condition(ie bumps). Sway bars are a good thing to tune the car once you have the spring rate within the ball park.