Problems With Stability On Track

[B1ack_Mi16 67]

This weekend I went to my first trackday ever with the 205 track car

 

Pic: http://ria1.zenfolio.com/p897910593/e3d967a5b

 

It's certainly fast. But there are some issues I have problems with.

 

It will wander all over the place when accelerating at the straights, pulls from side to side and not possible to hold it straight.

 

It's got a Quaife ATB and 309 arms and driveshafts.

 

Anyone running much power and still has a rock stable acceleration?

 

Also a mate of mine said it had too little grip at front. I'm running 300lb/in springs and the dampers I bought from Chris on here some years ago, originally for his 309 set up for tarmac.

 

Still.. any ideas how to set this thing up properly to gain grip and stability?

[Goliath 94]

I am running approx. 190bhp and 200lbs/ft torque with standard suspension all round (pretty much) including 205 wishbones with all standard bushes and bearings up front (Standard diff too). I find it is OK in a straight line under full throttle but not brilliant, it will normally stay very straight unless I hit a white line or cats eye or any imperfection in the road surface, then it will start to veer to one side.

 

I have a lot to do to my suspension though as I currently have no rear ARB so handling in the corners is atrocious, I am planning on running AVO coilovers on the front with ~280lb springs, not entirely sure on what to use on the back yet but it will be made to match.

 

I think DrSarty is running a power figure a lot closer to yours, I believe he has no problems but will let him answer that.

 

I would imagine having the 309 wishbones wouldn't be helping with torque steer. What top mounts do you have as this could affect it too, and of course the usual culprit of dodgy wishbone bushes, when were yours last replaced?

[EdCherry 34 1 Cars]

My money would be on wishbone bushs

[kyepan 291]

when the bushes go on that set up it just feels more vague when cornering, and of course exhibits the lift off, left, accelerate right power steer characteristic on the straights, but it doesn't sound like what your describing.

 

An mi with diff and 309 bones and 0deg toe, will pull like a git on uneven surfaces, snatching from side to side as it grabs grip, it probably tries to remove your arms with 240bhp.

 

How much do your wheels weight? as reducing the weight and therefore gyroscopic torque of the wheels will definitely give the steering a lighter feel, especially when torque is pulling it off center. Also large discs will also create more gyroscopic torque...and make it worse. Moving from smr's to c5's and nearly halving the weight of the wheel, made the car much nicer to drive, it reduced the torque steer, and lightened the steering considerably. I would say it was 50% better, but not completely cured, although heavy disc's didn't help. Alloy bells or light discs and the lightest alloys you can fit around them should reduce the weight of the steering when it does grab...

 

Stopping it becoming very sensitive and moving from side to side, may be something someone with more knowledge of suspension can answer. I would guess the amount of power exerted upon the car and its suspension will cause the geometry of the wheels to change slightly, either because it's lifting the front and inducing some kind of bump steer, or it's just twisting everything out of shape and ruining the geometry once again.

 

 

J

Edited May 26, 2009 by kyepan

[DrSarty 90 1 Cars]

I'm no suspension expert that's for sure. My car's approx 225-230BHP and 196lbft of torque and I'm lucky enough to not be suffering any torque steer or wandering at all.

 

I have 205 wishbones but with yellow poly bushes, -35mm Eibach springs and group N turret top mounts. Everything else is standard.

 

That doesn't mean things are perfect, as I seem to trash driveshaft CV knuckles (outer ones) very quickly - a combo of torque and plate diff induced damage I guess, coupled with inferior remanufactured driveshafts - and also oval hub carrier balljoint holes.

 

The latter produces a nasty dive in on right hand bends, depending on power applied, and snatches mid turn which removes confidence in the car and ruins the feel.

 

A combination of the above I feel also contributes to 80-95mph wobble, a bit like wheel in balance. That's one thing I want to get rid of in the new project, which is one reason for having custom parts, all steered by the need for more robust driveshafts. However the car seems to hunker down past 100mph and get solid again, although I don't have confidence in the car at these speeds which is another reason for the new project approach. What I mean is there's so much drama, wind noise from an ill-fitting door that I really don't feel that safe at very high speeds.

Edited May 27, 2009 by DrSarty

[James_R 3]

I'd check;

 

Tyre pressure (stiffer sprung 205's are very sensitive to this)

Front tracking

Wishbone bushes

Bottom ball joints

BBJ hub hole

Track rod ends

Steering rack bolts

Play in steering rack

draging brakes

 

All these things will have a negative impact on the car's handling, ATB's are known for being snatchy, but more on uneven/loose surfaces a mill pond smooth track should be no problems. Camber won't really make the car unstable on a smooth surface either.

 

Good luck getting to the bottom of it, always frustrating, but the Eureka moment is all worth it

 

*shameless plug*

 

Get a plate diff

Edited May 27, 2009 by James_R

[B1ack_Mi16 67]

My car is running SL 434's and Yokohama A048 semislicks.

(I must say it became a completely different car when I was running it with some studless winter tyres for approval reasons, very easy on the steering etc. and nicer to drive, but of course no grip at all).

 

Also the brakes are the 206 RC discs and 406 Brembos so quite some more weight there than normal setup.

 

Wishbone bushes are red polybushes from rallydesign, no slack what so ever in this setup (barely driven the car before).

There's no slack in the balljoints either (not oval hub carrier either) so it is not the normal worn bush/joint feeling.

 

It will pull the car like crazy occillating to both sides so I need to use 2 lanes when accelerating.

 

Engine has about 205lbft and 250-260bhp at 8000rpm (still rising).

 

I'm suspecting it's the Quaife that's working against me and making it pull like this.

But I will take the subframe down and go over all bolts etc. to ensure everything is good.

 

Top mounts I'm running are spherical bearings, concentric ones at the moment, but will change to eccentric later on...

 

Think I will try to adjust the toe settings a little bit. Just put some marks on where it is set now (set to standard 205 gti values). But when accelerating it will pull more toe in to the suspension, so maybe it's an idea to set the static toe to more toe out?

[welshpug 1,668]

have you had the tracking checked and ensured that the steering rack is centred when the wheels are in a straight ahead position?

[B1ack_Mi16 67]

Yes the tracking was set slightlly Toe in as to 205 gti standard spec.

 

The car became much better/more stable after this but still not good enough.

 

But it must be possible to fix it somehow anyway because some mates had a 400bhp 205 gti with T16 engine earlier and they said that one actually was more stable...

[bales 1]

I almost have the opposite problem to you, when driving normally i.e not accelerating my car seems to wander all over the road and feel pretty unstable.

 

My steering is very light around the straight ahead up to about 15 degs either way and then only weights up when you get any decent cornering force and stays light (unaturally light) I would say when driving normally.

 

It seems to respond very quickly to tiny changes in that light area which makes the car feel very unstable at speed To the point that I have no confidence driving the car fast....I don't know whether it is a symptom of the set-up, I have no weight in the rear and running 300lb front springs with GAZ adjustable coilovers set at mid points front and back. But I do not get any understeer it just wants to oversteer as soon as it gets close to the limit which is pretty scary and you can almost feel the back end turning in more than the front.

 

Though to get back to the original point, the only time my car is stable is when it is under full throttle and the weight is off the front wheels as much, then it tracks nice and straight

 

I perhaps have 190bhp and 220+lbft...

 

To be honest the handling is putting me off going on track (which is what I built the car for) as I have no high speed confidence in the car...

[welshpug 1,668]

standard rear torsionbars perchance Bales?

 

 

I think most cars here run no toe in at all.

Edited May 27, 2009 by welshpug

[bales 1]

standard rear torsionbars perchance Bales?

 

Yeah....

 

Though I always thought that a stiff front and softer back promoted understeer...

Edited May 27, 2009 by bales

[B1ack_Mi16 67]

Yeah....

 

Though I always thought that a stiff front and softer back promoted understeer...

 

Same as mine, mine is running standard 309 beam at rear with normal gti.

It's not really understeering either, but might be due to Peugeot Sport Bilstein tarmac rear dampers which are stiff.

 

As your car gets stable when accelerating it seem to me like you're getting toe-in under acceleration and hence it gets stable.

But at normal driving you suspension is toeing out and making it unstable.

 

However my problem is much different as mine is rock stable at normal driving, it's just under hard acceleration it gets almost impossible to control.

[bales 1]

Same as mine, mine is running standard 309 beam at rear with normal gti.

It's not really understeering either, but might be due to Peugeot Sport Bilstein tarmac rear dampers which are stiff.

 

As your car gets stable when accelerating it seem to me like you're getting toe-in under acceleration and hence it gets stable.

But at normal driving you suspension is toeing out and making it unstable.

 

However my problem is much different as mine is rock stable at normal driving, it's just under hard acceleration it gets almost impossible to control.

 

If it isn't directly suspension related as you said all your components were new etc...

 

Then couldn't it just be a function of that much power through the front wheels. Torque steer is created as you have uneven length driveshafts that have different gyroscopic forces acting on the wheels, if you couple this with your diff which is constantly going to be shunting power from one side to the other with your amount of power then couldn't it just be this....

 

If you think of touring cars and the crazy suspension geometry they run to get the handling...

 

If you couple that with standard suspension components i.e bushes that might not be designed to take the loads you are putting through them and suspension geometry that isnt really cutting edge (i.e compared to renaults and fords revo-knuckle etc... that reduces the scrub radius), then it might not be one single thing but more a number of smaller issues.

Edited May 27, 2009 by bales

[CaptainK 11]

However the car seems to hunker down past 100mph and get solid again, although I don't have confidence in the car at these speeds which is another reason for the new project approach. What I mean is there's so much drama, wind noise from an ill-fitting door that I really don't feel that safe at very high speeds.

I'm glad I'm not the only one that doesn't feel safe doing those speeds in a 205. (I hardly notice I'm doing those speeds in my FTO though ). Gotta love the 205 then for the thrill ride it gives you.

[James_R 3]

What condition are the rear bump stops in?? might be sitting on one more than the other casuing the ossilations (sp??)

 

Do you have solid beam mounts??

 

I'll confirm I always have the 205's I've had set to zero toe, makes for an awesome turn in, but can make it feel like it always wants to turn in the straights, but no issues on track

[B1ack_Mi16 67]

What condition are the rear bump stops in?? might be sitting on one more than the other casuing the ossilations (sp??)

 

Do you have solid beam mounts??

 

I'll confirm I always have the 205's I've had set to zero toe, makes for an awesome turn in, but can make it feel like it always wants to turn in the straights, but no issues on track

 

My bumpstops are removed at the rear..

 

I think I will try to adjust toe settings a little. First maybe to some more toe in, if it doesn't help I might just as well try to set it to some more toe out.

 

A mate of mine has a 205 8v turbo with 220bhp approx and he is getting the same behaviour on uneven roads, but his was stable at the track, he's just got a normal open diff so might be this that triggers it.

 

My rear beam mounts are solid and the beam is refurbed and in mint condition, the rear feels very stable and firm.

[welshpug 1,668]

I wouldn't run without bumpstops, this gives a very abrupt end to travel and hence grip.

[andychalmers 0]

I had similar problems on my 205 S16 rally car, only running 180bhp. The car on tarmac was zig zagging really bad, it just wanted to pull to the side, very hard to drive. I found 2 problems, one was the inner joint of the long shaft was falling apart and the other the diff was set too tight for tarmac, its a ZF diff set at I think 160 nm (115 ft lb). I changed the diff to a Tran X with I think 75 nm and this helped loads. You say you have a Quaife which is not a plated diff but could this be part of your problem? especially if you've checked everything else.

[B1ack_Mi16 67]

I had similar problems on my 205 S16 rally car, only running 180bhp. The car on tarmac was zig zagging really bad, it just wanted to pull to the side, very hard to drive. I found 2 problems, one was the inner joint of the long shaft was falling apart and the other the diff was set too tight for tarmac, its a ZF diff set at I think 160 nm (115 ft lb). I changed the diff to a Tran X with I think 75 nm and this helped loads. You say you have a Quaife which is not a plated diff but could this be part of your problem? especially if you've checked everything else.

 

Yes I think the Quaife might be contributing to this, not that I know it is but anyway.

Although from what I've heard the Quaife is supposed to be very nice and calm in the way it operates...

[Anthony 1,003]

Quaife's can "hunt" for traction and alternately send power from one wheel to the other - it doesn't "lock-up" like a plate diff does - which could give the symptoms that you're experiencing.

 

As has been said, unless you've enough power to be breaking traction at speed the Quaife shouldn't be throwing you all over the place on a smooth track - my suspicion would be that something on the car isn't quite right somewhere and that's causing the Quaife to try and compensate, but you've checked what sounds like the obvious candidates.

 

Might be worth putting an open diff back in and seeing how the car behaves then, assuming that it's road legal and you can test it on the road? If nothing else, with an open diff it might be more obvious what the problem is as it won't try and send power from one wheel to another.

[B1ack_Mi16 67]

True, car is now road legal.

 

If I'm hard with the clutch shifting from 3'rd to 4'th gear it certainly will spin the wheels on normal road even when running semi slicks.

 

On the track however it seem just to be getting grip in 3'rd so I avoid wheelspin, maybe why it's hunting so much then.

[James_R 3]

Check the steering rack wear, bolted tightly to the subframe, subfrma ebolted up to the car and Track rod ends

 

As ant says if the ATB is moving the torques around then any play in the steering will make the car move about.

 

I'd say it's more typical of an ATB to move the car round like this than a plate which just locks down and drags you straight

 

If you're totally stuck then I'd be willing to let you put your engine in my 205 to see if the characterisitcs are repeated

Edited May 27, 2009 by James_R

[welshpug 1,668]

just a thought, are you using wheel-spacers at all on the driven wheels?

[B1ack_Mi16 67]

just a thought, are you using wheel-spacers at all on the driven wheels?

 

Yes need to in order to clear the Brembos with the SL 434's...

And haven't found any other wheels that fit without yet...

 

I must add the car is the most stable I've ever driven as long as the throttle stays fairly closed and at normal driving.

 

And very eager to self adjust the steering to zero. So hard to turn in other words.