Car Feels Unstable Under Power

I have only had my car about 3 months and driven it less than 1,000 miles. The car has Steeda shocks and linear lowering springs, everything else stock.

I have noticed the "dartiness" or what feels almost like torque steer but not through the steering wheel. Basically when on the highway under power, every bump or dip in the road causes the car to veer off track, the steering wheel ALWAYS reacts to everything, and I feel like I am constantly sawing at the wheel to make the car run straight or where I want. Good way to describe it is say I am in a turn on the highway, under at least half throttle, I hit a dip in the road, the steering wheel goes LIGHT for a second as the suspension compresses, which makes ME now steer incorrectly since just second prior I had the right amount of tension on the wheel to go the direction I wanted. Now suddenly with the wheel lighter in feel, I caused the car to oversteer and have to correct. Then the car recovers from the dip and steering goes stiff again, AGAIN I oversteer since I had just corrected from the lighter wheel feel. I am not talking about like 1ft dips I am talking small changes, maybe a 4-6" dip in the road.

Same kind of feeling happens when the tires start tracking in the ruts of the road. This I am used to happening, but the same steering wheel issue happens, causing me to really swerve around as I go on and off the ruts in the road.

Also say I am rowing through the gears 1-2-3, after every hard shift the car usually makes a hard left or right pull once the power comes back after the shift, causing me to serve back.

Is all this normal and innate to the s550 platform?

What wheels and tires? Sounds like from the amount you lowered, you're getting quite a bit of bumpsteer. What are your alignment settings?

Firstly, my S550 was prone to tramlining stock. Once my factory alignment was thrown away for my first alignment done at a performance alignment shop... took care of that. That and the steering, even in the sport modes, is far too light on these cars. Needs to be BMW heavy.

Therefore I'd say this is typically an alignment issue but you gotta get used to how the car acts with stiffer front springs. I experienced this exactly when I went from Steeda Ultralites to Swift Spec R on my 20" wheels with summer tires. I switched to 19" wheels with Conti DWS A/S tires and it went away. Then I went and got a new alignment with the 20" wheels and the issue was gone - toe got screwed up. How so significantly I don't know, maybe weight balance change or something.

I do have a bump steer kit from Steeda, though, but I really don't think that was the issue. I have lowered a few folks' cars with or without Steeda shocks and springs and didn't happen to them, but it happened to me so I feel your pain. I now have 350 rate front springs and I am not experiencing this anymore no matter what wheels/tires I run.

Probably worth calling Mike D at Steeda for alignment specs.

I have never owned a lowered car before, so a lot of this is new to me. Always ran factory height everything.

Bump steer is exactly what most of it is, forgot that was the name for it.

I am running factory PP rims, pilots up front and conti DW extreme out back. Have spacers all four corners.

I don't have the alignment specs as I purchased it this way and have not had it to any shops yet, but the suspension was installed at Steeda.

TooSoonJunior said:

I have never owned a lowered car before, so a lot of this is new to me. Always ran factory height everything.

Bump steer is exactly what most of it is, forgot that was the name for it.

I am running factory PP rims, pilots up front and conti DW extreme out back. Have spacers all four corners.

I don't have the alignment specs as I purchased it this way and have not had it to any shops yet, but the suspension was installed at Steeda.

Click to expand...

pm your contact info. More than happy to help you with your concern.

Thanks,

Mike D

I experienced many of the same issues as the OP. Bumpsteer kit plus alignment and new tires fixed that for me. The new tires made a big difference and I'm not feeling every little thing through the steering wheel anymore.

DWs on the rear have less grip than the front PSS also. Would improve if you got full PSS

ForTehNguyen said:

DWs on the rear have less grip than the front PSS also. Would improve if you got full PSS

Click to expand...

Good point, more so for handling but not true straight line. Conti's hook pretty damn good straight line.

TooSoonJunior said:

I have never owned a lowered car before, so a lot of this is new to me. Always ran factory height everything.

Bump steer is exactly what most of it is, forgot that was the name for it.

I am running factory PP rims, pilots up front and conti DW extreme out back. Have spacers all four corners.

I don't have the alignment specs as I purchased it this way and have not had it to any shops yet, but the suspension was installed at Steeda.

Click to expand...

There's where a lot of it's coming from. Going to spacers changed your scrub radius and gives the tire a lot more leverage on the knuckle. Bump steer is made much worse with increasing scrub radius.

BmacIL said:

There's where a lot of it's coming from. Going to spacers changed your scrub radius and gives the tire a lot more leverage on the knuckle. Bump steer is made much worse with increasing scrub radius.

Click to expand...

The scrub radius of my belly seems to keep increasing... :frusty:

It looks sooo damn sexy though lol







The wheel spacers I mean....

TooSoonJunior said:

It looks sooo damn sexy though lol







The wheel spacers I mean....

Click to expand...

Yes, the spacers lol

By all means keep them, as the higher scrub radius also improves steering feel quite a bit. You may need to get a bump steer adjustment kit, however. Do you still have your alignment sheet?

I am going to check and see what I have, don't believe I still have the original alignment sheet.

Mike @ Steeda called me directly and gave me a full run down on ways we can get this thing settled down. A+++ for customer support and follow through. I will post back once I see the results of adjusting my tire pressure and getting the IRS located and car fully aligned. Those are the suggested steps.

TooSoonJunior said:

I am going to check and see what I have, don't believe I still have the original alignment sheet.

Mike @ Steeda called me directly and gave me a full run down on ways we can get this thing settled down. A+++ for customer support and follow through. I will post back once I see the results of adjusting my tire pressure and getting the IRS located and car fully aligned. Those are the suggested steps.

Click to expand...

Yeah those are good steps.

The bump steer through corners is just mildly aggravating, wheel sawing back and forth and constant correction to hold a line. Didn't change when I went to BFG Comp 2 A/S from the OE PZero summers. I've not yet had an alignment done though, but lots of mods in the rear IRS/Diff.