Dualing out oversteer in ITR DC2

[beeker]

So our DC2 targa car is a bit throttle off tail happy. Not every time, only when you dont need it!! (that 1 in 50th corner with the big drop)

Anyway, its got std factory front and rear sway bars, new Koni's, and 450 front springs, and 250 rears. That being the case, where do i start?

Does the spring rates affect rear end stability ? or sway bar only ?

[EVLTEK FBI AKL]

hmm DC's almost always understeer!!

you could try a few things... bigger rear tyre - softer spring rates - more positive camber in rear, run toe more neutral - run a smaller sway bar (I think some EG models have a smaller on).

[Shadow Sol]

rear chamber kit should sort you out - or maybe as adam said try a smaller sway bar - EG2's run a 15mm one if that helps

[-KONIG-]

I would always check wheel alignment first, then look at tyre pressures! before taking performance loosing parts off the car!

[dazznz]

Originally Posted by beeker

So our DC2 targa car is a bit throttle off tail happy. Not every time, only when you dont need it!! (that 1 in 50th corner with the big drop)

Anyway, its got std factory front and rear sway bars, new Koni's, and 450 front springs, and 250 rears. That being the case, where do i start?

Does the spring rates affect rear end stability ? or sway bar only ?

Are we talking for targa? Or track? For targa my car ran 450lb in rear and 500lb in front. And i think we both no that this car has a very well proven targa history. This was also with koni and with a mugen rear sway bar. Managed to get a 7th and 9th in stages at the bambina last year on this setup so i think it works pritty well. What tyre size do you run? i dont see this being an issue. Also look at tyre pressures. When tyres are hot they should be 30-32psi

[-KONIG-]

springsa rates will affect the stability moreso than the sway bar! even with stock suspension the 22mm rear swaybar made the car stick like shit to a blanket!

Hard springs do not allow for any bump or deviation in the road when the car is loaded up through a corner, which inturn will bounce the back of the car up loosing traction! A swaybar will only keep the car flat, regardless of spring rates!

[dazznz]

also dont muck around with the front sway bar

[beeker]

Originally Posted by dazznz

Are we talking for targa? Or track? For targa my car ran 450lb in rear and 500lb in front. And i think we both no that this car has a very well proven targa history. This was also with koni and with a mugen rear sway bar. Managed to get a 7th and 9th in stages at the bambina last year on this setup so i think it works pritty well. What tyre size do you run? i dont see this being an issue. Also look at tyre pressures. When tyres are hot they should be 30-32psi

We're talking targa. Our car originally had 500 front and 400 rear, with a mugan 24 rear sway (when purchased from the same people who sol yours to you, thus the simialr setup). We reverted the rear sway to std 22mm, and reduced the front to 450 (or was that 400), and the rear to 250. Also running konis. I will say that our front bump rate wasnt high enough, and it had the occasion bottom out. Front what i've rear increasing the bump rate also decrease oversteer. Also we're running 225/45/16. In regard to tyre temps, we did some work on this a while ago, but now were on the wider rubber, i need to recheck this.

I guess thats where we'll start... (with the new shell!)
Bambina, yea, it bet you in my AE86!! 34 against your 43

[beeker]

Originally Posted by -KONIG-

springsa rates will affect the stability moreso than the sway bar! even with stock suspension the 22mm rear swaybar made the car stick like shit to a blanket!

Hard springs do not allow for any bump or deviation in the road when the car is loaded up through a corner, which inturn will bounce the back of the car up loosing traction! A swaybar will only keep the car flat, regardless of spring rates!

I was thinking of softening the rear, not increasing it.
Is there a 20m rear sway bat for the DC2 ITR ?

[dazznz]

Originally Posted by beeker

We're talking targa. Our car originally had 500 front and 400 rear, with a mugan 24 rear sway (when purchased from the same people who sol yours to you, thus the simialr setup). We reverted the rear sway to std 22mm, and reduced the front to 450 (or was that 400), and the rear to 250. Also running konis. I will say that our front bump rate wasnt high enough, and it had the occasion bottom out. Front what i've rear increasing the bump rate also decrease oversteer. Also we're running 225/45/16. In regard to tyre temps, we did some work on this a while ago, but now were on the wider rubber, i need to recheck this.

I guess thats where we'll start... (with the new shell!)
Bambina, yea, it bet you in my AE86!! 34 against your 43

lol yer you did. However it was the 1st time i had ever driven my car. Sceary experience the 1st time.

Well its your call man, but the guys that set up our two cars new what they were doing. I no that my car has not problems going dam fast through targa, and has no problems with understeer. How low have you got the thing sitting? because this can also affect it. I no my car is quite high, so maybe this is the difference.

[BigAl]

sudden lack of grip on the rear of a front drive car can often be caused by :

binding in the rear suspension . solution . remove rear springs and move suspension throught full travel . nolethane rear bushes are a big problem here

hitting rear bump stops . solution . run tie wraps on shock rods to ensure car is not running out of bump travel

rear alignment . solution check rear alignment and increase toe in by a small amount

insufficient rear camber .

weight transfer on power off. when trailing or dropping the throttle in turns weight is transferred to the outside front from the inside rear . this is often sufficient to reduce rear traction to a level where the rear will slide . it is often combined with an increase in understeer [loss of front grip ] and can be solved by a slight increase in spring rate all round and an increase in compression rate to the front

what are your current aligmnent settings ?

a day at the track with a tyre pressure gauge, pyrometer and alignment gear will give you plenty of info

you may also want to experiment with a slightly higher rear rates ..say 350

[BTLF3D]

Originally Posted by beeker

I was thinking of softening the rear, not increasing it.
Is there a 20m rear sway bat for the DC2 ITR ?

i have a 20mm whiteline on my eg, which should fit ITR

[americ_ian]

Originally Posted by EVLTEK

hmm DC's almost always understeer!!

you could try a few things... bigger rear tyre - softer spring rates - more positive camber in rear, run toe more neutral - run a smaller sway bar (I think some EG models have a smaller on).

msut be the driver, i had nothing but slight over steer

[nitrous]

Have you checked the condition of your RTA bushes? Worn ones can cause nervous off-throttle oversteer. And related trouser-soiling... 8O

[2HEKTK]

Originally Posted by -KONIG-

I would always check wheel alignment first, then look at tyre pressures! before taking performance loosing parts off the car!

My ITR used to do this on the Taupo Track at turn 5 the long right hander just as I throttle off and am about to apply the brakes. As Andrew said I adjusted tyre preasure slightly and got a wheel alignment which cured the problem. Probably not always the case but the cheapest way to start.

[M3_Power]

Originally Posted by 2HEKTK

My ITR used to do this on the Taupo Track at turn 5 the long right hander just as I throttle off and am about to apply the brakes. As Andrew said I adjusted tyre preasure slightly and got a wheel alignment which cured the problem. Probably not always the case but the cheapest way to start.

That's lift off oversteer you are describing .... left foot braking before lift off to balance the car is your friend in these situations

[DanSir]

Im am slightly confused as from everything thing I have
ever heard, one of the ITR's best loved charactoristics was its slight throttle off oversteer, giving it slight rear wheel drive like handling out of corners meaning combined with the LSD a very early acelleration point.

I suppose though a more neutral setup might be preferable in a situation like targa?

Anyway interesting topic.

[tysonzane]

Interesting you run quite a soft setup which i always reccomend for tarmac rallying. Upon seeing the video of your incident it instantly looked like you were running very heavy springs in the car and some over dampened bilsteins but as it turns out this isn't the case.

I'm running a slightly softer spring in the rear and alot softer spring in the front compared to you. I'm not sure if the effect of a large (IMO) gap between the weight of the front and rear has on the car. If it was my car i'd be running a softer spring in the front in general but i'm unsure if this will fix the over steering issue.

I'd start with camber kits front and rear and a decent allignment. I run .5 negative degree in the rear which has proven to work a treat on tarmac.

What tyre pressures where you running at the start of the stage where the incident occured? I check my tyres like a mad man at the start and finish of most stages and it is definately something to stay on top of. Also i think you've over tyred the car and i've found going to wider tyres actually had made cars more want to snap sideways on tarmac rally surfaces.

Remember Tarmac rallies are completely different to circuit racing you cant compare the two and you shouldn't spend lots of time and money testing on a circuit to build a suspension setup for rallying.

[Coupe-R]

My ITR used to do this on the Taupo Track at turn 5 the long right hander just as I throttle off and am about to apply the brakes. As Andrew said I adjusted tyre preasure slightly and got a wheel alignment which cured the problem. Probably not always the case but the cheapest way to start.

Turn 4 is what got me the first time Mark, oversteer like mad with cold rears or too much pressure in the rear in lift off over steer.

In fact Turn 2 can be a good one for this on cold tyres Quite fun

[dazznz]

Originally Posted by Coupe-R

Turn 4 is what got me the first time Mark, oversteer like mad with cold rears or too much pressure in the rear in lift off over steer.

In fact Turn 2 can be a good one for this on cold tyres Quite fun

Turn 2 can be alot of fun. In the last race i did down at taupo i got to the front of the pack off the start only to find that when i got to turn 2 i had way to much pace on for cold tyres and ended up spinning off the track.

[CamB]

Well I've got a 15mm EG sway bar that you can try out if you like, but I reckon it'd handle terribly - understeer like a pig.

This might well be one of those individual driver preference things - some people like a wayward tail and are prepared to just commit to throttle back on whenever its a problem. It's not for me... I'm not that good, but I like a car that turns in.

What are your old alignment specs - that could be the problem.

[dazznz]

Originally Posted by CamB

Well I've got a 15mm EG sway bar that you can try out if you like, but I reckon it'd handle terribly - understeer like a pig.

This might well be one of those individual driver preference things - some people like a wayward tail and are prepared to just commit to throttle back on whenever its a problem. It's not for me... I'm not that good, but I like a car that turns in.

What are your old alignment specs - that could be the problem.

I have just accquired one of these bars, and a standard type r one and i am going to be doing some testing to compare them all. However this will be track work so i dont no how relevant this will be

[CamB]

My (limited) experience - what'd I be comfortable with at the track is far snappier than on an unpredictable and bumpy tarmac stage, so it may not be too conclusive for you

[beeker]

Originally Posted by tysonzane

Interesting you run quite a soft setup which i always reccomend for tarmac rallying. Upon seeing the video of your incident it instantly looked like you were running very heavy springs in the car and some over dampened bilsteins but as it turns out this isn't the case.

I'm running a slightly softer spring in the rear and alot softer spring in the front compared to you. I'm not sure if the effect of a large (IMO) gap between the weight of the front and rear has on the car. If it was my car i'd be running a softer spring in the front in general but i'm unsure if this will fix the over steering issue.

I'd start with camber kits front and rear and a decent allignment. I run .5 negative degree in the rear which has proven to work a treat on tarmac.

What tyre pressures where you running at the start of the stage where the incident occured? I check my tyres like a mad man at the start and finish of most stages and it is definately something to stay on top of. Also i think you've over tyred the car and i've found going to wider tyres actually had made cars more want to snap sideways on tarmac rally surfaces.

Remember Tarmac rallies are completely different to circuit racing you cant compare the two and you shouldn't spend lots of time and money testing on a circuit to build a suspension setup for rallying.

We had an alignment done 4 weeks prior to the event, and done by wairau alignment who i trust. But.... Now i think about it we did get the 4x wheels bearings proactivly replaced which may have been after teh alignment. Not sure what unbolting was needed here ?

Tyre pressure. 25psi cold front and rear which most the guys run. Some drop it 1psi in the back.

Tyre size. YEs i would prefer to run 215 or 205, but the 03G only come in 2x 16" sizes 225/45 and 205/55, and the 205's are too tall so 225 it was. or maybe i should accept that for a narrower tyre.

[beeker]

Originally Posted by BigAl

sudden lack of grip on the rear of a front drive car can often be caused by :

binding in the rear suspension . solution . remove rear springs and move suspension throught full travel . nolethane rear bushes are a big problem here

hitting rear bump stops . solution . run tie wraps on shock rods to ensure car is not running out of bump travel

rear alignment . solution check rear alignment and increase toe in by a small amount

insufficient rear camber .

weight transfer on power off. when trailing or dropping the throttle in turns weight is transferred to the outside front from the inside rear . this is often sufficient to reduce rear traction to a level where the rear will slide . it is often combined with an increase in understeer [loss of front grip ] and can be solved by a slight increase in spring rate all round and an increase in compression rate to the front

what are your current aligmnent settings ?

a day at the track with a tyre pressure gauge, pyrometer and alignment gear will give you plenty of info

you may also want to experiment with a slightly higher rear rates ..say 350

BigAl, have you looked at the in car video of the crash ? Tell me what you think.
http://www.youtube.com/watch?v=pU-tKU6Ye7k

I will also note that on targa last year we had some issues with bottoming out the suspension on the front. We were going to increase the bump rate in the front , but we didnt quite get to that. I read that increasing front bump rate increase understeer and reduces oversteet - maybe i should have!

On some other news, we have decided to reshell it. A repair was cheaper, but repairing a bent cage gives me the shits.