Car Too Firm/skittish/struggling For Grip.

[No Crust Racing]

S13, but that shouldn't matter.

See video and not that in the long left hander at 0:41 and 1:43 how the nose of the car seems to want dart around a bit. All throughout the video you can see how skittish the car is. Last time I drove here it was much more progressive, I've added swaybars since then and I'm guessing the whole setup is too firm now.

And this is before the bars went in and starting from turn 1.

Here's what's in it/the alignment, let me know what you think. I did the alignment with a stringline, took 6hrs going up and down allowing the car to be settled again then re-measuring. I had no success with local shops.

So after A LOT of stuffing around it now has the following and "looks" a lot better.

Front - Camber/Toe (can't tell you what castor is, arms are stock). Considered maybe less camber might give me a better contact patch if the car is now not leaning over as much with the swaybars.
Driver: -2.75/1mm toe out
Pass: -2.75/1mm toe out

Rear- Camber/Toe
Driver: - 1.3/1mm toe in
Pass: -1.3/1mm toe in

Car has BC BR Coilovers with 8kg Front and 6kg rear springs - maybe these are too firm?

Whiteline 27mm front swaybar (adjustable and on max soft)

R32 GT-R rear swaybar (25mm hollow)
New end links both ends.

Federal RS-Rs 235 all round, was running about 29-30psi hot on that day. Maybe I'm just at the limit of what these tyres can do?

I'm yet to get under it and have a look at how the tyres wore, but the car was a late more skatey than usual, not sure if that's because the swaybars are allowing me to go faster or because something is wrong.

Yes I realise I am also a shit driver and smoother inputs will help

[bcozican]

Did you use the same spring damper before and after ?

I would have thought before putting sways in the coilovers were taking alot of the load to stop body roll hence you having to run a harder setting on the coilovers?

Now you have decent sways the coilovers dont need to run double duty as such and take the anti roll job as much hence if using the damper rate as before your now too stiff....you should be able to soften the damper rate off to allow each part to do its job now

[No Crust Racing]

I actually didn't touch them, and I should have at least checked them.

If I recall they are both close to, if not already on, max soft.

[GTSBoy]

I'm thinking a couple of things.

1) Like you and bcozican, I ponder if the overall suspension rate is too high. If your coilovers have very stiff springs and you have added stiff ARBs, then you will possibly have too much roll rate.

If you have wound the damping on the coilovers back to full soft (or even at the soft end) then it is very possible that you simply have too much spring (spring and ARB) rate for too little damping. As your very first order of business I would suggest that you look to winding the dampers up to half way, or perhaps stiffer and try again. The reason I say this is that if you are underdamped on stiff spring rates, then it will certainly skip around and be skittish. There isn't enough damping for the spring rate.

2) It is just possible that the ARBs that you have added have unbalanced your previous setup. Assuming it had good front-rear balance before, putting semi-random ARBs on top of that setup might have stiffened the front a lot more than it stiffened the rear. If that has happened, then it will want to understeer more. It certainly looked and sounded like it was understeering more in the long left hander. Admittedly, that will also happen if the damping isn't right, per my first thought above.

If your ARBs are adjustable, you could try softening the front one as much as you can. That will shift the grip balance forward a bit. Be aware though that if the real problem is unsufficient damping, then it could end up feeling better anyway, simply because you have backed off on the total roll rate at the front. Also be aware that if the problem is not in the balance, if it is instead simply too much spring rate for the damping, then softening the front without softening the back may well make the skippy behaviour worse at the rear.

[No Crust Racing]

The ARB at the front is adjustable and on max soft, as in the connection points are farthest from each other.

I'm just getting details on going 6/4kg spring rates instead.

[bcozican]

^^ all that

also if all that is done and still a little unbalanced would it be a case of if you are now cornering harder and faster that front camber specifically (and may rear) might have to be increased a little bit also so that your not rolling over on the tyre? and increase turn in

[No Crust Racing]

I'll get under the car when I can and see how the tyre wear looks also, as I'm yet to check that.

[No Crust Racing]

Spoke to BC who suggested I speak with Paul at option1, he recommended returning to the stock front swaybar and testing that, leaving spring rates alone. Then swapping that around and putting the stock rear back in but leaving the front.

That's a fir bit of f**king around at a paid track day but it's not impossible.

I might take both bars, go and run a session with it as it is, and see how those times compare to previous Winton times then look to swap a bar out and test again.

Federal said my hot tyre pressures are fine.

Paul also said my alignment settings were on the money.

[No Crust Racing]

I put it on stands last night after packing up all my gear from the track day.

Interestingly the outside edge of the tyres front and rear looks darker/more worn.

Which I thought would imply it needs more camber.

Talking to a buddy of mine with a very similarly setup car (but better and wider tyres) he runs -3.5 front and -2.5 rear with the same bars and spring rates (although Tien RS and no BCs).

[No Crust Racing]

Two other things.

I'm being advised to get some adjustable castor arms and dial in more positive castor and was also asked to look at the angle of my LCAs, which are definitely not parallel upfront. Cross member side sits lower than wheel side which as I understand it is not good for Roll Centre,

[GTSBoy]

Car is too low.

[No Crust Racing]

Realistically, I should be able to raise it up and not have a heap of extra roll with those swaybars and springs.

[No Crust Racing]

How high is "right" though, front LCA's parallel at least?

[GTSBoy]

Essentially, yes. It's about the arc that the arms swing through and the induced camber changes etc etc blah blah. If the arm is horizontal then the wheel is at the widest point of the circle/arc when at rest/zero position. Any disturbance up/down changes the relationship of the wheel to the road and the car less when set up this way than when the wheel is up above that diameter line. Know what I mean? Different suspension designs suffer to varying degrees. Skylines hate being too low. Silvias, with struts at the front, probably aren't as bad.

Then you start to get into more serious questions about where the roll centre is located. Perhaps you should google up the question and look at what happens when the roll centre is too low. There are some great books you can buy that will open your eyes a lot if you're interested enough. I recommend this one http://www.amazon.com/Race-Car-Vehicle-Dynamics-Experiments/dp/0768011272

[No Crust Racing]

If I raise it, I'm going to lose some neg camber also, so may also need camber bolts - but then strut clearance starts to become an issue.

A few people are jumping up and down about how I am still running stock caster arms also - which should give me more neg (dynamic) camber if I understand it correctly.

[GTSBoy]

A few people are jumping up and down about how I am still running stock caster arms also - which should give me more neg (dynamic) camber if I understand it correctly.

Yes. Correct. And for a track car especially, the free dynamic camber you gain is worth a lot.

[No Crust Racing]

OK so raise the ride height, and get some castor arms.

I also have ties to the local BMW dealership who are happy to run over the car on their laser aligner for mates rates.

Any indication of what ride height should be in the rear? Front seems to be, get arms parallel, what about the rear?

OH I may also grab some camber bolts.

Edited April 1, 2015 by ActionDan

[No Crust Racing]

Also, what about the rear end.

The only suggestion there was more camber.

[GTSBoy]

I wouldn't go more camber at the rear unless you want less drive traction. As to height, again the lower arms want to be close to parallel. If it was a Skyline you could look up the recommended eyebrow heights and use that as a guide. Silvias might be different measurement for the same actual height though.

If you lift the front, and the back then looks low......then lift the back too!

[No Crust Racing]

I'll make sure they're even'ish.

I'm only talking more camber as that's what other, faster cars, are doing.