As the title says, the car likes to sway left or right when hitting bumps at highway speeds. Even with the minor bumps on the road, I'm getting a noticeable amount of feedback in the steering wheel shifting left and right.

While I'm on wide open throttle, it's nearly impossible to keep it in a straight line when it hits a bump. I tend to veer either to the left or right lane and have to quickly correct it.

I currently have:
BC Racing Coilovers - dampening is set to the middle.
Tanabe front sway bar with adjustable end links
Stock rear sway bar
Work Emotion XD9
18x10 +38 front
18x10 +18 Rear
Nitto Motivo 255/35/18 all around.

I'm not too knowledgable in the suspension world. Where would be the first place I check for worn suspension parts that could be causing this?

 

I'd check your adjustable sway bar end links. They may be too loose; they are meant to be mean tight to prevent the sway you speak of.

You need to understand the amount of force it takes to keep the car straight, which is the sway bars job. They are under an ungodly amount of force at all times to keep the car from swaying.

So, I'd check there to start.

Also, does the car rock from side to side while coming out of a turn? If so, that is definitely the sway bars being too loose.

 

What are the condition of your bushings, pillow *****, and toe links/trailing arms? Check your alignment and tire pressure?

 

By 'sways' do you mean the vehicle leads or drifts during single jounce/rebound event?

Are you lowered/raised from nominal ride height? I'm not familiar with the toe/camber curves of the FD but am curious if you may be operating in an area that has increased bumpsteer.

Curious also what your individual/cross caster is, an alignment check with a decent hunter can give that information.

Not attempting to put down your setup, but that seems a fair amount of wheel/tire up front... what was your reasoning for this setup?

 

And maybe inner and outer tie-rods.

 

Also, a simple case of low air pressure or having the alignment off will cause similar problems. Start with the simple stuff.

 

In addition to other good comments above, the wide front wheels will a bit lower offset will also make the front of the car more sensitive to road irregularities.

What tires do you have? All matched, good new-ish rubber?

 

Get an alignment, you probably need some toe

 

I think your springs are too strong for the shock. Or the shock can't dampen the spring. If the shocks are relatively new and not leaking, check the suspension.

Check your front lower ball joints by going over a speed bump normally. If your steering wheel rotates back and forth rapidly then your lower ball joints are worn out.

The rears can be checked with the car on jackstands. Grab the rear wheel at 12 and 6 o'clock and move to and fro parallel to the drive shaft. If it rocks more than a quarter inch, you need to replace the lower joint.

I find that it's best to replace all the suspension with rubber or steel bushings in them after 75K of street.

 

Your pillow ***** are probably shot. My car is almost as clean as they come and at 82k miles all 6 were garbage. The rear end would sway a bit hitting a bump just right on the highway. Had the whole mess rebuilt/replaced. Whole new car!

Jason

 

I remember one time out in California I hit a bump on I-5 by the Citadel Outlet Shops and my car kicked out a bit.

 

Yea, stiffer springs on oem shocks is one of the worst suspension mods you can do on any car. I've never had a car ride well with stock shocks and aftermarket springs. Still, that usually causes the car to be bouncy. I would check the pillow *****, bushings, alignment, and air pressure like I said.

 

His original post says he has bc coilovers.... don't think it's a issue of lowering springs with stock shocks....

I agree with dale, get a alignment check. Incorrect toe or camber will cause it to be unsteady while hitting a bump. That will be the easiest step to start with.

Firestone has lifetime alignments for $170... can go as much as you want and if you become friends with one of the techs he can set it to whatever specs you want....

 

Thanks for everyone's help. I took the car back to NTB to have the car realigned. Everything is within spec. The body has about 87,000 miles on it. My next guess is that the bushings might be worn out. I'm not too sure how to tell since suspension is not my forte. I'll try to do a little bit of reading to see if I can eyeball/feel it to determine if the bushings are worn out.

 

One other thing to check is the preload on your shocks. A friend of mine had his screwed up and the car rode terribly as well. Just a thought and something to double check.

 

87k miles the pillow ***** are shot and the rest of the bushings/end links/etc arent too far behind or are already worn out. Basically same miles here and all 6 pillows were shot, same with basically everything else.

Jason