When i got the 2017 IS350 I immediately noticed that the car liked to bounce side to side, this is when driving at around 20 to 25mph when you really notice it. Its small bounces but it became kinda annoying even the wife started to notice.

So I got Tein coils since I wanted to lower the car anyway, so i hoped it would address the issue, but nothing changed.

Im not sure if its only me I dont seem to see anyone posting about their IS bouncing side to side. These are just little bounces kinda like somone shaking the car. NOTE: it doesnt happen all the time, it happens when there are slight uneven surfaces on the road.

What do you guys think? Do you guys have it too? What you change to make it go away?

I was actually thinking of this performance damper from trd but im not sure if it would help.

 

Did you ever address this with the dealer? What did they say?
I don't have a 350, but I've never seen anyone post with an issue like what you're describing.
It sounds like either a wheel issue or suspension issue.

 

Ya that doesn't sound right... if you can duplicate the problem as you wish, take it back to the dealer and bring a tech with you and show him the issue. That TRD damper you're referring to actually exists on your car already, but not as stuff as the one TRD offers.

Also, if you're talking about uneven roads, no other place on the planet will compare to Alberta Canada (where I live), and I don't experience the issue you're talking about... so definitely something not right there.

 

I was never able to ask the dealer about it. After changing rims still had it. And even after changing coils still there. So i dont think its with anything oem rims or suspension. Hmmm injust wanna explain further about the bounce. The bounce are really small but it bounces multiple times enough for me to notice.

agh im not sure if im explaining it right lol.

anyways 2 different people told me to rplace sway bar so im thinking about doing it hopefully it fixes it

 

It almost sounds like you are describing a loose control arm somewhere in the rear suspension. I would have the dealer check for anything loose on the rear arms to see if That is the cause.
I am having a similar issue but mine feels like the rear sways side to side. Going to have the dealer check it out.

 

I do notice the bounciness on Sport+ mode during a turn on a uneven pavement. But not all the time. It almost feels like one of the shock is blown and it is not.

 

I feel bounciness on turns with uneven pavement too and im lowered on ark gt springs. It's mostly when im on the freeway at 60 mph+ and doesn't really happen going street speeds. I'm not sure if it's something to do with my shocks, alignment, or tires.

Does anyone know if very slightly stretched tires could be causing it because of not enough sidewall? I have hankook v12s with 225/35/19 on the front 8.5" wheels and 255/30/19 on the rear 9.5" wheels. The tires have a more rounded hbsidewall and I feel like maybe with the very slight stretch there's not enough support on the sidewall when hitting those uneven roads during a turn causing it to bounce and throw off balance? Any input would be appreciated

 

I did noticed this when I switched from the factory turanzas to Michelin Pilot Super Sport. Maybe there is too much grip on the rear? causing a more understeer? idk. I'm pretty much stock other than RR-Racing USRS kit.

 

I take it back, I think my front driver's side might be leaking.

 

Just came back from the dealers regarding the leaky shocks. They said they it has to leaking at a certain level (level 3 or lower) for them to replace it. Although my front driver side shocks have more oil residue compared to others it is well within the specs.

So it is something else thats causing the bounciness.