Unstable above 80mph

[ze12o]

What can cause my car to become unstable and twitchy at highway speeds? It's very tiring driving the car long distances. I just gotten an alignment. It drives like the tie rods are going but those were replace recently and they are still tight. I'm being a little vague because i'm not sure what info is needed. I can tell you anything from alignment specs to all parts that were replaced.

-Kev

[HIGHFIVEBETA]

It's a midget in your wheel well fucking around with your tie rod ends when you drive fast.

[mowgli 240sx]

^^^ he needs an answer, not a smartass remark
c'mon florida

hope you find the solution to your problem

[!Zar!]

Custom alignment?

Stock tension rods?

Lower offset wheels?

Low profile tires?

[KiLLeR2001]

Get coilovers, hicas rear sway, and a rear strut tower bar. And if you want, a funcitonal wing that produces downforce.

[Xplat]

is your car slammed? are you running hella frush wheels?

[Nismo240driftSX]

Differential?

[ze12o]

Originally Posted by HIGHFIVEBETA

It's a midget in your wheel well fucking around with your tie rod ends when you drive fast.

I fucking knew it.

Originally Posted by mowgli 240sx

^^^ he needs an answer, not a smartass remark
c'mon florida

hope you find the solution to your problem

Thanks haha

Originally Posted by !Zar!

Custom alignment?

Stock tension rods?

Lower offset wheels?

Low profile tires?

Stock alignment with -2.5 camber front and back
SPL tension and tie rods, Tie rods are spaced to be parallel with the control arm

Originally Posted by KiLLeR2001

Get coilovers, hicas rear sway, and a rear strut tower bar. And if you want, a funcitonal wing that produces downforce.

Fortune auto coils
Tanabe F sway
Progress R sway
F&R STB
EM racing c pillar bar
Stealth custom's tension arm brace
Circuit sport rack bushings
Rear subframe inserts (not solid ones)
Roof wing? lol

Originally Posted by Xplat

is your car slammed? are you running hella frush wheels?

No, My friends still call me 4x4 I have a 2 finger gap in the front and 1 finger gap in the rear iirc 17x8 +38 F w/15mm spacer 17x9 +35 R no spacer Proper size tires 235/40 starspec & 255/40 federal ss591?

Originally Posted by Nismo240driftSX

Differential?

S15 diff

Thanks for the input!

[Croustibat]

car lowered without bump steer correction i guess... it surely finished off every bushing in the suspension.

How to cure the decease:
change every rubber bush for new ones (get oem bushes or rose/ball joints for suspension ones)
get bump steer correction tie rod ends. Install. Get a new alignment. Enjoy.

[Croustibat]

Crap, you posted before i hit submit.

Originally Posted by ze12o

Stock alignment with -2.5 camber front and back

Get -1 camber at the rear, you dont need more. -1.5 max (i.e 1°30")

Are you sure your alignment has been done correctly ? BTW you cant get correct toe on the rear with stock toe arm, and you need to lengthen the rear traction arms when lowering because otherwise it messes with your toe arc (basically you need to tilt the knuckle towards the back to keep the toe arm connexion at the same place as before lowering)

Originally Posted by ze12o

No, My friends still call me 4x4 I have a 2 finger gap in the front and 1 finger gap in the rear iirc 17x8 +38 F w/15mm spacer 17x9 +35 R no spacer Proper size tires 235/40 starspec & 255/40 federal ss591?

It just means your friends dont know much about cars.

It really sounds like uncorrected bump steer, and you car is still quite a lot lowered (I am running the same wheel specs , same front tyre , and i can put a lot more than 2 fingers at the front while still being already lowered )

Beware, your speedo is messed up with that rear tyre. I also think the stagger may be a part of it. Why did you put a 255 cheap tyre there ? larger tyres require less camber too ... with -2.5 camber i bet you are not even using half of the tyre.




edit : Could be another reason : your sway bars are loading the lower arms when they should not. This is the hardest part in setting coilover height with non adjustable ARB droplinks. It would produce a very weird effect, similar to bump steer.

[Croustibat]

Originally Posted by CyrusMccasl

hope you find the solution to your problem

I hope a giant gorilla rapes you and then tears you slowly appart

[ze12o]

Get -1 camber at the rear, you dont need more. -1.5 max (i.e 1°30")
Stock ruca so no real adjustment just whatever it is from the drop I don't remember if that's the correct number. I will check tomorrow.

Are you sure your alignment has been done correctly ? BTW you cant get correct toe on the rear with stock toe arm, and you need to lengthen the rear traction arms when lowering because otherwise it messes with your toe arc (basically you need to tilt the knuckle towards the back to keep the toe arm connexion at the same place as before lowering)
Alignment shop is no performance place but the guy is very good and has the top of the line hunter machine. But he wouldn't know about what you're talking about. lol
I'm guessing I'm going to need to buy ruca and traction arms?


It just means your friends dont know much about cars.
They really don't They are the hard parking type, slammed to the floor, form over function. I don't listen to them much.

It really sounds like uncorrected bump steer, and you car is still quite a lot lowered (I am running the same wheel specs , same front tyre , and i can put a lot more than 2 fingers at the front while still being already lowered )
Maybe 2 1/2 finger I have fat hands so who knows. lol

Beware, your speedo is messed up with that rear tyre. I also think the stagger may be a part of it. Why did you put a 255 cheap tyre there ? larger tyres require less camber too ... with -2.5 camber i bet you are not even using half of the tyre.
Speedo's not off my much. Long story short I fucked up I had 255 in the front and 275 in the rear. Feds all around. Drove like shit so I swapped front to rear and bought new front tires.

edit : Could be another reason : your sway bars are loading the lower arms when they should not. This is the hardest part in setting coilover height with non adjustable ARB droplinks. It would produce a very weird effect, similar to bump steer.
Any fix for this? iirc the rear links are adjustable. Fronts are stock links with energy bushings

BTW my head just exploded. Thanks for the great info.

ninja edit:
I agree with the gorilla rape.

[lude4life13]

Take your front spacers off, drive it, and see if that fixes it. If it does then your spacers arent on correctly or are crappy quality.

[ze12o]

Need them to clear brakes. They are ichiba bolt on with hub centric rings. :]

[iLagX]

maybe your wheels are bend?
possible bad tires?
rack n pinion bushing is shot?
steering column bushing?
lower control arm bushing/ball joints

[mad-ass]

what brand wheels? there is a good reason to buy name brand wheels and it's because most knock-off wheels aren't made very square.

i know my knock-off aren't square at all, easy way to find out is to jack up your rear end so both rear wheels are off the ground and on jack stands, start the car put it in gear, get the wheels speed up to 35/40 mph ish and look at the rear wheel itself to confirm. the edge of the wheel should not be "wobbly" or going in and out etc.

[Croustibat]

Originally Posted by ze12o

[...]

You need RUCAs for camber, rear traction and toe arms for toe (you cant adjust toe correctly either with stock arms) . the length of the rear traction arm depends on the height of the car so i cant tell you exactly how much.

You need a bump steer gauge to get the correct length (build one for cheap or buy one - around 80$ for the cheapest)

As for ARB droplink, you have some choice:
First set coilover height with disconnected droplinks (you can keep them in place, just unbolt them from the lower arms), then bolt one front and 1 rear.
Then:
1/ fine tune height until you can check there is no /very little load on the arms. If you cant because the chassis is bent or if it looks odd, add shims to change the ARB bush position up/down.

2/ get it corner weighted. Corner weight will tell you if it is loaded or not. Either pay for it or make a cheap DIY setup with 2-3 mechanical home scales per wheel.

3/ get adjustable droplinks Whiteline makes some. You can have some done too but it will cost nearly the same (around 100-120€ / pair)

You can feel that ARBs are loading one side of the car mostly when your suspension goes on droop / compression. The car feels weird, just like one side lifts higher than it should.

You could also start to worry about roll center correction, which i would suggest if you drive fast, but then it is going to cost money again.

Your best bet, if you can, would be to change the knuckles for lowering ones. They lower the car without messing with geometry (basically they offset the wheel bearing bolting points), letting you keep the OEM arms and geometry. It can be a money saver over changing every suspension arm in your car.

If you want to learn more about geometry i suggest motoiq.com suspension tech articles for introduction, then zilvia's thread about roll center correction

[thefro526]

There are a lot of good ideas in this thread, some of which are way over my head, but have you tried checking the simple stuff?

I've had similar problems when my wheels were out of balance. Cruising at highway speeds and I'll get a consistent 'wobble' of sorts. The problem was corrected by having my tires balanced.

Also look into how your wheels are sitting against the hub. Many after market wheels come over-bored to fit as many applications as possible. This prevents the wheels from sitting concentric with the hub - a set of $10 hubcentric rings usually fix this problem.

[KiLLeR2001]

Sigh, problem solved. This dude doesn't even have adjustable RUCAs or rear toe arms. I adjusted my camber about -1.5 degrees and it messed up toe bad. The rear end was all over the place and felt very unsafe.

Get fully adjustable arms and a proper alignment to spec and you won't have anymore issues.

[ze12o]

Originally Posted by iLagX

maybe your wheels are bend?
possible bad tires?
rack n pinion bushing is shot?
steering column bushing?
lower control arm bushing/ball joints

1 wheel is bent on the lip but It never effected the driving.
Tires still have a lot of meat on them
I can change the bushings but they seem pretty tight last time i checked.
stock steering column bushing
stock lca bushing

Originally Posted by mad-ass

what brand wheels? there is a good reason to buy name brand wheels and it's because most knock-off wheels aren't made very square.

i know my knock-off aren't square at all, easy way to find out is to jack up your rear end so both rear wheels are off the ground and on jack stands, start the car put it in gear, get the wheels speed up to 35/40 mph ish and look at the rear wheel itself to confirm. the edge of the wheel should not be "wobbly" or going in and out etc.

Yokohama Super Advans Sa3r On the balance machine they looked fine.

Originally Posted by Croustibat

You need RUCAs for camber, rear traction and toe arms for toe (you cant adjust toe correctly either with stock arms) . the length of the rear traction arm depends on the height of the car so i cant tell you exactly how much.

You need a bump steer gauge to get the correct length (build one for cheap or buy one - around 80$ for the cheapest)

As for ARB droplink, you have some choice:
First set coilover height with disconnected droplinks (you can keep them in place, just unbolt them from the lower arms), then bolt one front and 1 rear.
Then:
1/ fine tune height until you can check there is no /very little load on the arms. If you cant because the chassis is bent or if it looks odd, add shims to change the ARB bush position up/down.

2/ get it corner weighted. Corner weight will tell you if it is loaded or not. Either pay for it or make a cheap DIY setup with 2-3 mechanical home scales per wheel.

3/ get adjustable droplinks Whiteline makes some. You can have some done too but it will cost nearly the same (around 100-120€ / pair)

You can feel that ARBs are loading one side of the car mostly when your suspension goes on droop / compression. The car feels weird, just like one side lifts higher than it should.

You could also start to worry about roll center correction, which i would suggest if you drive fast, but then it is going to cost money again.

Your best bet, if you can, would be to change the knuckles for lowering ones. They lower the car without messing with geometry (basically they offset the wheel bearing bolting points), letting you keep the OEM arms and geometry. It can be a money saver over changing every suspension arm in your car.

If you want to learn more about geometry i suggest motoiq.com suspension tech articles for introduction, then zilvia's thread about roll center correction

Thanks you've been a great help. I will probably go to rt tuning to do a full alignment

Originally Posted by thefro526

There are a lot of good ideas in this thread, some of which are way over my head, but have you tried checking the simple stuff?

I've had similar problems when my wheels were out of balance. Cruising at highway speeds and I'll get a consistent 'wobble' of sorts. The problem was corrected by having my tires balanced.

Also look into how your wheels are sitting against the hub. Many after market wheels come over-bored to fit as many applications as possible. This prevents the wheels from sitting concentric with the hub - a set of $10 hubcentric rings usually fix this problem.

I never actually thought of that. Ill measure the bore when I get off this weekend

Originally Posted by KiLLeR2001

Sigh, problem solved. This dude doesn't even have adjustable RUCAs or rear toe arms. I adjusted my camber about -1.5 degrees and it messed up toe bad. The rear end was all over the place and felt very unsafe.

Get fully adjustable arms and a proper alignment to spec and you won't have anymore issues.

I wouldn't say that much, I've been lower and never had this problem. Maybe it's taken a toll on my stock bushings.

Thanks everyone for the input. I hope I get this fixed. Next paycheck will be dedicated to fixing this problem.

[S14DB]

Are your wheels balanced?

[blueshark123]

The speed limit is not 80 so you should be fine driving your car the at the correct speed..........

I hope you know im sarcastic

[iLagX]

doesn't matter if your tires has alot of meat!! if it has humps and bumps due to bad shocks it will cause steering wheel to shake at high speed

[Matej]

If it is just the steering wheel that jerks left and right aggressively out of nowhere, then the problem may be in the power steering system.
If the whole car feels shaky, it is most likely the tires/wheels, or possibly wheel bearings.

[!Zar!]

Was the car twitchy before the alignment?

Was the car twitchy after the alignment?

Made made you decide to align your car?

[ze12o]

Originally Posted by S14DB

Are your wheels balanced?

Yes

Originally Posted by blueshark123

The speed limit is not 80 so you should be fine driving your car the at the correct speed..........

I hope you know im sarcastic

You got me. lol

Originally Posted by iLagX

doesn't matter if your tires has alot of meat!! if it has humps and bumps due to bad shocks it will cause steering wheel to shake at high speed

Not shaking, more like bump steer unstable.

Originally Posted by Matej

If it is just the steering wheel that jerks left and right aggressively out of nowhere, then the problem may be in the power steering system.
If the whole car feels shaky, it is most likely the tires/wheels, or possibly wheel bearings.

What would the power steering effect? I actually have a shitty ps pump that always leaks.

Originally Posted by !Zar!

Was the car twitchy before the alignment?

Was the car twitchy after the alignment?

Made made you decide to align your car?

Yes, Changed worn out spl rod ends
Yes, twitchy after as well. Less violent though with the new rod ends
Changed tension rods, tie rod ends and rear sway.

[mad-ass]

since you did just get alignment done...

let's see some numbers off of that print out.

i'm mainly looking for...
Toe: F/R
Caster: F
Thrust angle:

should explain some things.

[Croustibat]

-2.5 camber with stock arms means toe is completely messed up anyway

[Matej]

Originally Posted by ze12o

What would the power steering effect? I actually have a shitty ps pump that always leaks.

This fellow's steering rack turned out to be bad.

[!Zar!]

Originally Posted by Matej

This fellow's steering rack turned out to be bad.

Wasn't his problem reversed power steering lines or something?