Steeda IRS braces

[Norm Peterson]

As it is now the car is pretty flat in corners and under braking, it does raise up under acceleration. Too much IMO.

I'm a little surprised that you're noticing pitch rotation under acceleration but not under braking. Most people tend to notice roll and nose dive under hard braking more.

The easy and arguably best fix would be firmer springs. That's if you really do need this to be fixed . . . how much of this perception of acceleration nose rise/tail squat is based on easy street driving where you don't ever get much?

FWIW, springs that provide wheel rates in the 225 lb/in - 250 lb/in range are not unreasonably stiff for street duty in a car of this weight, provided that the damping is somewhere near right. This would be about where Blue's Option 2 falls.

I'd like it to be as flat as the Steeda Q500 in the above Vid, but that might beat me up in daily driving. ;)

Videos tend to downplay the amounts of chassis inertial movements, and they certainly don't provide all of the sensations you get from actual sitting-in-the-driver's-seat observation. Chances are, the Steeda car is still rolling about 2°/g including tire deflection effects. I doubt a stock S550 rolls more than about another half a degree per g above that.


Norm

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[Norm Peterson]

He must have washed that Vette with apex repellent before taking it to the track.

comes in a value-pak with Zaino, doesn't it?


Norm

 

[K4fxd]

Under hard braking the car dives very little, I don't get a bad feeling. If say I'm going 60 and floor it, it feels like the front wheels are going to come off the ground, and I am looking at the sky.

It is real flat in corners, so much that I wonder if the springs are upgraded. But before I braced it up it rolled a lot more.

 

[Norm Peterson]

Under hard braking the car dives very little, I don't get a bad feeling. If say I'm going 60 and floor it, it feels like the front wheels are going to come off the ground, and I am looking at the sky.

It is real flat in corners, so much that I wonder if the springs are upgraded. But before I braced it up it rolled a lot more.

​

Stick? Automatic? Tuned?


Norm

 

[K4fxd]

It's auto, I have leg injuries that won't allow me to operate a clutch in traffic and this is my daily driver.

I get the same rise from a standing start.

No tune at this time

When you drive it fast it falls apart and

I've flogged it pretty good in a large empty parking lot, Putting the car at its limits. I've spun it and had the front end wash out. Right now it is pushy loose, the front wants to give up, if I give it throttle it spins.

 

[TeeLew]

comes in a value-pak with Zaino, doesn't it?


Norm

If you get it from Costco, ya.

 

[K4fxd]

I weigh 220 and I sat on the fender the car dropped about 9/16 of an inch. That makes my wheel rate around 300.

What is a good wheel rate on these.

 

[Norm Peterson]

I weigh 220 and I sat on the fender the car dropped about 9/16 of an inch. That makes my wheel rate around 300.

It won't be that high. Front sta-bar stiffness carries some of your weight across the car and compresses the other side's spring, so you've got two springs working, one of them more than the other. If you measured how much the car dropped on both sides, you'd have a much closer idea about wheel rate.

With huge roll stiffness, your wheel rate would be much closer to 150.


Norm​

 

[TeeLew]

It won't be that high. Front sta-bar stiffness carries some of your weight across the car and compresses the other side's spring, so you've got two springs working, one of them more than the other. If you measured how much the car dropped on both sides, you'd have a much closer idea about wheel rate.

With huge roll stiffness, your wheel rate would be much closer to 150.


Norm​

I mostly agree. First, this is not nearly high enough resolution of a measurement to draw any conclusions, but it's an interesting mental experiment, so let's play.

As Norm says, this is going to take the entire end of the car into account. Let's say you sat in the middle of the hood at axle centerline to make our life easier. That takes the FARB twist out of the equation. You will compress the springs, but there are all sorts of other things to take into account. The FARB bushings are bonded to the bar. That's a spring. All the control arm bushings have to deflect, more springs. The damper will resist motion due to gas pressure...a spring. Where are you taking your measurement? If it's body to ground, then you'll have tires and other things to take into account. Further, there will be all sorts of friction/stiction in the system which will provide uncertainty in measurement.

Take all this into account, and it gets tough to answer your question with any real confidence.

 

[Norm Peterson]

It's auto, I have leg injuries that won't allow me to operate a clutch in traffic and this is my daily driver.

I get the same rise from a standing start.

With an automatic . . . at speed, you'd be getting a commanded downshift and an abrupt increase in acceleration. From a dead stop, there will be momentary torque converter stall ratio torque-multiplication effects in addition to allowing the engine to 'slip' up to where there is more torque than there is at idle and off-idle where normal street use starts from.


Norm

 

[K4fxd]

Just got the Steeda support bushings, fingers are crossed. Also will be going to 3.55 gears at the same time.

Car should be a lot more fun.

Norm, not sure what you are trying to say in your last post

 

[Norm Peterson]

Norm, not sure what you are trying to say in your last post

That an automatic is likely to yank the nose up further, either on a foot-to-the-floor commanded downshift at speed or on a moderately aggressive launch. That you're more likely to notice it with an AT because none of your attention is being tied up with operating a shift lever and a clutch pedal.


Norm

 

[K4fxd]

Yea, I get that but it feels to me like there is not enough rebound dampening in the struts.

Definitely going to go with Bilsteins or the Ford track struts and shocks.
Pedders has an inexpensive coil-over setup. Is it any good.

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