A couple of weird issues - fixed?
 

Alright so to give a bit of background, I have 18x9.5 wheels with 255 section summer tires which are all grip no slip. Before you go asking why I'd take the fun out of a tail-happy car, I know I know.... it's in preparation for FI. But at the moment, with stock power, it's glued to the road no matter the temperature or if the road is dry or wet.

Lately what I've been experiencing is weird side to side motion during fast cornering, like on an off-ramp for example. You know how on stiff coilovers your car kinda bobs up and down through a corner? Well mine's doing that side to side. Is that just a side effect of all that grip? What can I do to mitigate that? I haven't had an alignment on these wheels yet, only on my winters, which are 18x8 or 8.5, can't remember. There is no rubbing, tramlining, so I wasn't exactly rushing to get an alignment. But I'm thinking the increased grip might be exposing a deficiency in something else.

The only other pertinent mods are rear subframe/transmission/shifter/diff bushings/inserts. The coilovers came with their own end-links. No sway bars, strut braces, or LCAs.

The second weird issue, might be related, is a bit more vibration coming into the cabin. I'm used to it due to all the bushings and like it, but it's now causing random parts of the car to resonate. First it was the passenger door window area just behind the A-pillar, then last night it shifted to the dash garnish around the head unit until I pressed it in, which sort of made it go away.

I might be thinking too much but I feel like the two issues might be related. Of course this could be simply due to the shorter sidewall making for less buffer between me and the road but I'm thinking something else might be amiss.

Appreciate your two cents.

EDIT: also there is a bit more vibration coming through the steering wheel

What actual parts are you using?

Meisterr ZetaCRD+ coilovers with the whiteline rear subframe, diff and trans inserts, and a perrin shifter insert

A bunch of inserts and bushings increase NVH. Fat, sticky tires will follow every imperfection in the road. Those coilovers aren't exactly high end. If one or both of the rears is blown, a sharp bump will make the rear move sideways. Lowering changes the alignment.

If you're not gonna get an alignment from a reputable shop who can also check everything out, you can try going to the softest settings and see if that changes anything. I don't think throwing parts at the car is the solution, unless something is broken or faulty.

-coilovers definitely aren’t the best and something I will be looking to upgrade in the future. Having said that, they’re good OEM replacements and aren’t super basic.
- i will get another alignment seeing as how the wheels and tires are different now. I did get it aligned after lowering but that was with different tires
- the effect from inserts and bushings was very positive and I’m glad I’ve done them. I don’t believe they’re the source of the issues, I just mentioned them for the sake of full disclosure of upgrades done thus far
- the side to side motion occurs continuously through the high speed corner. It’s not a single event. It’s predictable and repeatable. Almost like the back end wants to step out but either the grippy tires or anti-roll bars push the motion back to the other side, which transfers it again to the outside and so on and so forth - just a theory.

shouldn't need alignment after new tires/wheels.

to me it sounds like damping. but stuff like this is really hard to diagnose over the internet.

Front knuckle ball joint might be loose. Will cause the toe slightly to change mid corner.


If you have the car up on jack and pull/tug outward on the wheel, it shouldn't lift or jiggle.

Thanks, I’ll ask my mechanic to take a look next time

If you did have it aligned, I'd blame the coilover or something loose/broken. I'm assuming the tires have more than a couple hundred miles on them. They can be squirrely when new.

So as a shot in the dark, I went and turned the coilover damper settings all the way to soft and then returned them all to middle setting, front and back. I believe before that I had the front firmer than the back. Immediately the car felt like its usual self. I took an on ramp at a good lick and did not detect any of that side to side movement. What does this mean?

underdamped - shock not controlling suspension motion, just bouncing along on the springs

overdamped - shock preventing suspension from moving, all the road variance goes straight into the chassis

Could be either based on the description but based on having the rear set softer likely the first one, which would jive with the 'shimmy' feeling imho.

Most adjustable shocks have more wrong settings than right ones.

Thanks. Man I can’t wait to get a better set of coilovers

'Good enough' can also get you really far, you may be able to play with them a bit and get somewhere happy.

I have. And every time I just keep coming back to the middle settings. I wonder if a part I’m missing may improve things and in what way. Like LCAs, sway bars, strut braces, whatever else I can’t think of or simply don’t know about. And even though I have all those bushings installed, there is still a fair bit of drivetrain slop. And where do i go from here. Only thing I don’t have is trans and engine mounts.