Suspension correcting itself

[Performance nut]

I honestly don't know what else to call this but it is an odd behavior I just noticed. Did not notice this prior to installing the Steeda "Stop the Hop" kit but I wasn't exactly getting on it before it was installed.

When going into a turn fairly hard, the car will start to understeer. So I give it a slight increase of throttle and counter with throttle oversteer. Car is handling predictably and right around the time I'm coming out of my turn... the car lurches and then I'm going straight. It was somewhat unnerving the first time but I have reproduced it multiple time in different situations. Every time it has been a positive result (car goes in the right direction) just unnerving to feel it do this.

It's almost as if the car suddenly gets more traction and then corrects itself. Why I'm bringing it up is because it feels uncontrollable for that moment it lurches that I feel that if I overdo/underdo something, I'll be spinning out.

The only mod on my non-PP GT is the aforementioned Steeda "Stop the Hop" kit. The alignment was just done after installing the kit so that is good. If you have some input or helpful insight, I'd appreciate it.

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[Nerass]

did you clock the bushings?

 

[Performance nut]

did you clock the bushings?

Not sure what you mean by that...

 

[Nerass]

http://www.mustang6g.com/forums/showthread.php?t=44129

 

[Nerass]

despite not lowering it, you still had to loosen everything

 

[Performance nut]

http://www.mustang6g.com/forums/showthread.php?t=44129

despite not lowering it, you still had to loosen everything

No, the front wasn't touched. The rear had a few but I don't believe all of them were messed with. Even so, none of this was done with load on the wheels so I will so no, my bushings were not clocked.

Though I am not getting any of the symptoms described in this. I don't experience "floating" and I wouldn't call this unstable, just twitchy. If one of the suspension vendors don't chime in, I'll call and see if this fits in the category described.

Thanks for pointing out the thread

 

[NightmareMoon]

Can you do better to explain the 'lurch'?

 

[Performance nut]

Can you do better to explain the 'lurch'?

It is somewhat hard to explain. It is a sensation of having a totally in control turn and then suddenly the car forcibly moves itself to each side in a very short period of time.

Another example is compressing a spring and then changing the force at which you are compressing it and the spring expands quickly. This is what I think is going on. I loaded the suspension up and as I'm exiting the turn, the compression force reduces and all the sprung force releases, literally pushing the car. The force compresses the other side and, as the force reduces, the opposite side pushes back.

 

[BmacIL]

Sounds like AdvanceTrac intervention.

 

[EricSMG]

Sounds to me like something is binding and then suddenly releasing.

 

[wildcatgoal]

Nothing in the Stop the Hop package would cause binding in the IRS. Perhaps the toe links, if installed improperly, but that's really hard to do (if not impossible).

I'd need a better description, but this sounds like an effect of the bracing and spherical bearing that you're probably not used to yet. I mean if the car is body-rolling the opposite direction it should, then that's weird. But if you are blipping the throttle after the apex of a turn, you're going to upset the car and it will have the effect of the car straightening out sooner than you might expect and be all kinds of unsettling, unless it was intentional and you know what you're going for. And generally it's not the best way around a corner (by the book, anyway).

I can replicate what I think you're experiencing in hard mountain runs, where I can blip the throttle just after the apex and straighten out and aim for the inside again, sneaking up on the car pacing me (in front) pretty quickly. The effect feels a bit like a minute sort of float feeling for a nanosecond but the car should not really feel as if it's shifting weight funny (mine doesn't). If I could pass, I would be able to (not enough space on 2-lane roads, etc.). Maybe a totally different thing happening, I am not sure. But the stop the hop package, which I have most of, significantly stiffens up the IRS so you should expect it to behave differently. Understeer is a natural element of these cars, a lot of it. At least my PP car was biased towards it quite a bit.

Perhaps add a little negative camber up front and/or dial some out of the back, which will help the car rotate.

EDIT: comes to mind that in order to install this package, you have to drop the IRS mounting bolts. Did you get an alignment after that? If not....................

 

[NightmareMoon]

When I had a rear swaybar that was set too stiff for the rest of my suspension, I would get a disconcerting sudden hop to the side as the car settled into a turn. Rear would skip about a foot to the side mid-corner, and only when driving near the limit. The solution to that was using a softer swaybar setting until I had some dampers which could better control the weight transfer in a corner.

But, from your description it sounds like you're trying too hard to fight the car's nautral inclination to understeer, instead of accepting that the car is biased that way from the factory. Forcing oversteer is just that. Forcing it. As you transition from forced-oversteer to straight line, the car is going from oversteer to normal understeer to straight and probably in a not too subtle way. That's my guess anyway.

So make sure you're extra slow and smooth with the control inputs (steering and throttle) from mid-corner to track-out. Make sure you're unwinding the steering enough as you add throttle and power out of the corner, and not holding a constant steering angle as you try to add power (called pinching the corner).

In the end you'll probably be happier if you take steps to reduce the understeer bias instead of trying to muscle through it. Wider front tires, slightly stiffer rear swaybar bias, and a bit more front camber usually do the trick. It gets you a more neutral handling car that transitions easily between understeer and oversteer with slight throttle inputs and far less drama.

 

[Performance nut]

Sounds like AdvanceTrac intervention.

Didn't notify me if it was...

Sounds to me like something is binding and then suddenly releasing.

Was another thought as well. BMR had a similar theory.

Nothing in the Stop the Hop package would cause binding in the IRS. Perhaps the toe links, if installed improperly, but that's really hard to do (if not impossible).

I'd need a better description, but this sounds like an effect of the bracing and spherical bearing that you're probably not used to yet. I mean if the car is body-rolling the opposite direction it should, then that's weird. But if you are blipping the throttle after the apex of a turn, you're going to upset the car and it will have the effect of the car straightening out sooner than you might expect and be all kinds of unsettling, unless it was intentional and you know what you're going for. And generally it's not the best way around a corner (by the book, anyway).

I can replicate what I think you're experiencing in hard mountain runs, where I can blip the throttle just after the apex and straighten out and aim for the inside again, sneaking up on the car pacing me (in front) pretty quickly. The effect feels a bit like a minute sort of float feeling for a nanosecond but the car should not really feel as if it's shifting weight funny (mine doesn't). If I could pass, I would be able to (not enough space on 2-lane roads, etc.). Maybe a totally different thing happening, I am not sure. But the stop the hop package, which I have most of, significantly stiffens up the IRS so you should expect it to behave differently. Understeer is a natural element of these cars, a lot of it. At least my PP car was biased towards it quite a bit.

Perhaps add a little negative camber up front and/or dial some out of the back, which will help the car rotate.

EDIT: comes to mind that in order to install this package, you have to drop the IRS mounting bolts. Did you get an alignment after that? If not....................

Professionally installed (ie, not me) and aligned to almost factory spec (asked for a little more camber). The thing is, I totally get what you are describing and have had that happen on an autocross (different car). It isn't that but yes, similar effect (except I actually spun out on the autocross).

Oh and agreed about the Stop the Hop kit. I didn't mean to imply it had a negative effect. Though it did have an effect which seems to be contributing to this. Like you said, likely I'm not use to what it is doing yet.

When I had a rear swaybar that was set too stiff for the rest of my suspension, I would get a disconcerting sudden hop to the side as the car settled into a turn. Rear would skip about a foot to the side mid-corner, and only when driving near the limit. The solution to that was using a softer swaybar setting until I had some dampers which could better control the weight transfer in a corner.

But, from your description it sounds like you're trying too hard to fight the car's nautral inclination to understeer, instead of accepting that the car is biased that way from the factory. Forcing oversteer is just that. Forcing it. As you transition from forced-oversteer to straight line, the car is going from oversteer to normal understeer to straight and probably in a not too subtle way. That's my guess anyway.

So make sure you're extra slow and smooth with the control inputs (steering and throttle) from mid-corner to track-out. Make sure you're unwinding the steering enough as you add throttle and power out of the corner, and not holding a constant steering angle as you try to add power (called pinching the corner).

In the end you'll probably be happier if you take steps to reduce the understeer bias instead of trying to muscle through it. Wider front tires, slightly stiffer rear swaybar bias, and a bit more front camber usually do the trick. It gets you a more neutral handling car that transitions easily between understeer and oversteer with slight throttle inputs and far less drama.

Agreed 100%. The stock tires are too narrow and the grip is just lacking and, even though it is less squishy now, the suspension is still too soft for my taste. And yes, probably not a good idea to induce oversteer but I'm trying to push to see what the car can do. 0.68 on the factory accelerometer is a dismal number for me and a bit disappointing. Like to have seen 0.8 before running into these issues but it is likely technique... old man is a bit rusty.

 

[Rebellion]

What are the consequences of this "pinching the corner"? I put throttle just after the apex (when I feel the lateral g's starting to reduce), but the steering wheel has not began returning to center position.

I believe I've always done this (not that I'm good or anything)...but on the 'stang it does behave sort of weird, like it oversteers a tad, then overshoots the other way, then it stabilizes in the right orientation, which when acceleration really happens. When the car stabilizes, it like it's launching forwards. Perhaps it's caused by the nannies, but I don't know. BTW, my suspension is stock still.

 

[NightmareMoon]

What are the consequences of this "pinching the corner"? I put throttle just after the apex (when I feel the lateral g's starting to reduce), but the steering wheel has not began returning to center position.

I believe I've always done this (not that I'm good or anything)...but on the 'stang it does behave sort of weird, like it oversteers a tad, then overshoots the other way, then it stabilizes in the right orientation, which when acceleration really happens. When the car stabilizes, it like it's launching forwards. Perhaps it's caused by the nannies, but I don't know. BTW, my suspension is stock still.

Its good you're trying to apply throttle at or just before the apex. That's hard enough to do. Unwinding as you add throttle is basic traction circle stuff. The consequence is you'll fishtail or/or spin as your added demands on the rear tires exceed their available traction.

You see, if you're truly cornering at the limit, then the rear tires have no extra available grip to spare for thrust, as their grip is fully committed to cornering. In stock form there is a cushion built it. The car reaches the limits of the front tires with still some traction left at the back (i.e. bias towards understeer), so with a stock suspension there is some safety net for getting on the throttle too hard too soon, or not unwinding as you power out.

With a balanced suspension, you try to back off the steering as you smoothly add power you can transition from cornering at the limit to proportionally increasing throttle and decreasing cornering loads, all the while fully using the tires available traction until you're through to the straight.

Unwinding is a harder lesson to learn with low-power momentum cars, but the Stang really can overpower the rear tires and spin you if you don't unwind as you add throttle. Good news is that habits like that are easy to practice on the street at normal speeds.

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