unstable car on highway

[Bigpappaholt]

i recently got an s2k with tein coilovers which i believe were lowered even more (prretty much no rear wheel gap). The tires were pretty badly worn in the inside on the rears and slighly more worn on the insides on the fronts. I mounted new rears b.c they were in desperate need (245/35/19). After mounting it seemed that the car became slightly more unstable on highway, very twitchy. I guess im looking for some solutions. would an alignment do the trick or am i gonna need to purchase new front tires... fronts are nitto 555 (75% tread) and rears are nitto invo. Also when i put the new rears on they were rubbing the wheel well so i raised the rear and the front a lil to fix that (lil more than a finger gap). if i get new fronts would runing 235/35/19 and 245/35/19 rear be enough stagger?

[flipngo]

Put the car back to stock

[Bigpappaholt]

Originally Posted by flipngo

Put the car back to stock

haha. thats not an option for me, i dont have the money for that, and i do like the way the 19s look thou.

[s2kx2]

Well then I think you will need to accept that the look of 19's has compromised the handling of your S. A very common problem when going to an over-sized wheel that requires severe modification to the suspension to gain some of that handling back. Do you have diff spacers and what is the offset of these 19s? Could be the offset is so aggressive that the camber has been pushed to the point of absurdity. Either way good luck and be careful.

[Bigpappaholt]

ya i know the handling wont be as good with 19s, but will matching front tires help, or just getting alignment be fine? also is the 235 Front 245 Rear ok?

[gomarlins3]

If you raised the car, you changed your alignment. Anytime you raise or lower the car, your alignment changes. You need to go get it aligned.

[Java Junky]

Sortin' out some ride that'z been "improved" by it'z previous owner'z no easy task . . . n' alodda the time'izz the reason that the previous owner'z partin' with it.

The difference in hoop width between front'n rear (stagger) is one'a the most influential itemz that determine the vehicle'z under'r over steer.
Put more rubber on'a road in'a front ('R less in'a back) n'you're increasin' Stewie'z already considerable oversteer.
Put less rubber on'a road in'a front ('R more in'a back) n'you're decreasin' Stewie'z factory preset oversteer.
Now, add in a bunch'a other suspension "modificationz" n' you've got your work cut out for you tryin'a determine whut'z doon whut.
So with the combination'uv other thingz tha'chuuve got goin' on there, this is only a fingerz-crossed guess, but decreasin' the difference in tire widthz between the frontz'n rearz (Goin' from 225z to 235z in'a front'n stayin' 245 in'a rear.) will more'n likely lean you more in the oversteer direction.
Good luck pappa,
Java

[H20]

Try lowering the tire pressure some. Just try it and report back.

[batguano]

You also might want to experiment with this.

http://www.rallylights.com/other/stuning.htm

[Bigpappaholt]

i was running 33 psi. i will try 31 here the next day or so to see if it helps

[Java Junky]

If you jus' increase'r decrease similarly, all the way around (front'n rear), the end result should be the same balance of under'r over steer tha'cha started with.
But if, say, you go more pressure jus' up front ('r less in'a rear) you'll move more in the direction of understeer, 'r less oversteer.
If you put more pressure in the rear ('r less in'a front) you'll move towardz more oversteer, 'r less understeer.

Any tests involving increasin''r decreasin' tire pressures should be made in no more than 2psi jumps with serious testin'n attention paid to the results.
Playin' fast'n loose with thingz that make you stick'll have you playin' fast'n loose right inta the roadside scenery in short order.
Use caution'n patience pappa.
Good luck,
Java

[ottokrat]

You might try flattening out your rear neg camber. I also don't like that twitchy feel that comes with a lot of rear neg camber (riding around on the inside edge of the tire), so I flattened mine out. Some people swear by rear neg camber - the more the better, but not me: I think there's a limit the amount of neg camber that I like. You might have some trouble flattening out the rear camber though if it's lowered.

[H20]

Originally Posted by Java Junky

If you jus' increase'r decrease similarly, all the way around (front'n rear), the end result should be the same balance of under'r over steer tha'cha started with.
But if, say, you go more pressure jus' up front ('r less in'a rear) you'll move more in the direction of understeer, 'r less oversteer.
If you put more pressure in the rear ('r less in'a front) you'll move towardz more oversteer, 'r less understeer.

Java

In my mind, which is VERY suspect, you have that backwards.
That bein said, when I got my car she was twitchy as hell. I lowered front and rears to about 30 and she settled right down. I'm now up to 32 front and rear and she feels good still. Dunno what it WAS though so this holds no water really. Coulda been me not being used to a resposive car..dunno.
with 19's you only have essence of sidewall! I'd hate feeling every pollen particle on the road but so be it. I figure with 19's, ONE psi will make the difference that 2 or 3 might make on 17's. There just isnt much volume in there! I'll bet ya he can calm her down with pressure adjustment.
Also different gauges will read different and some may read different then themselves if they are bad quality.
None of this will fix the wear issue though. May, and most likely DO, need a camber kit.

[Java Junky]

'Good point H2.
'Seen more'n a few that didn't respond as the formula said they should've.
As fer gauges: fer most work, the run'a the mill unitz kin pull duty'z well'z anythin' else, but for final eval, you break out the unit that's been proofed'z accurate'n'izz kept in it'z own padded drawer'uv the toolbox.
You know . . the one that you gauge all the other gauges by.

N''z'fer wear . . everything'z a tool. You use it to get done whu'cha need'ta get done. Like &@^#, wear happenz.
Java

[chazdawg35]

Well Java does nitrogen have a good advantage.

[Java Junky]

Snug-up yer seatbelt dawg, this'un'z almost'z much funn'z the oil debatez.
(Engage the disclaimer ray if you would Scotty.)
In all honesty, I see nitrogen'z nothin' but'a doo-nothin', unrealistic'n unnecessary expense.
Stewie'z cool'n'all . . budd'itt ain't the SR-71, y'know?
N'z much fussin'n primpin'att we do with Stewie, it's'a car'n'itt'z driven on the ground. It'z got car wheelz, car tirez'n all it needz is car air, checked on a routine basis'n set to the appropriate pressures.
But hey! If bein' able'da tell folkz yer runnin' nitrogen in yer tires makez ya feel good . . gopher't.
Yuh only get one go-'roun'. 'Might'z well enjoy't, right?
Java