I recently got my car back on the road for the warmer season and I'm trying to tame some suspension issues during high speed driving.

My current setup is Tokico Illuminas with GC sleeves. Last year I upgraded my 500in/lb springs on the front to 600in/lb springs, and moved my 500in/lb springs to the rear. I like the increased response in corners, but I'm not in love with the unsettled feeling I sometimes get when I hit a dip or small bump at 100+ mph. It almost feels as if the car is jumping up after every imperfection and nearly wants to leave the road.

I don't feel as though the car continues to bounce more than once when it hits a dip and I've seen no evidence that my struts may be leaking. The struts still provide a noticeable difference in dampening when I adjust them, and I don't remember this being such an issue the last time I was driving the car. Maybe I'm just at their dampening limit with my current spring rates?

I'm not ready to throw down $700 for some new Koni Yellows, though I imagine that would certainly be a nice improvement. Is there anything else I'm missing that I could try to stabilize the car a bit more?

 

Those spring rates are beyond the functional capability of your dampers. If you're not prepared to match the correct dampers with those springs, reduce the spring rates.

 

Has your mystery car been aligned? Are the bushings ok? Other suspension parts ok?

 

That's kind of what I was thinking. I guess I need to decide whether it's worth the effort to swap my 400's back on, or just start saving for the Konis. Driving slow isn't a viable option.

The mystery car has only been eye-balled with string and had minor tweaks since being put back together. A professional alignment is on the to-do list as soon as I find the time. I still need to decide what alignment specs I want to go with that are best suited to my driving habits before I take it in.

All suspension components are good. New upper and lower ball joints up front, new tie rods, new upper control arms, new radius rod bushings. The rear has remained mostly untouched with the exception of some new adjustable upper arms and zero'ing out camber as much as possible.

 

You may opt to get it aligned before barreling down the highway at 100mph, smashing into bumps.