Can you elaborate?

Beside that, I think we'd prefer to explore all the usual culprits for these issues before giving up and saying that the car is inherently flawed.

 

Yes - I edited my post.

 

Thank you for clarifying @LaZeR , that sounds really disconcerting... Though, probably a bit more unique to your GS 300, since the OP seems to be having an issue just riding down the highway in general.

Wait. Do you know how old the tires are? It's possible they sat for a long time and have flat spots.

https://www.tirerack.com/tires/tiret....jsp?techid=11 if you haven't had to do this before.

 

@ @arentz07 hence my posts on this thread. For me the issue takes place only around (slight) bends at moderate speeds, which is why IMO @ @Jatnieln's issue might be even more serious, but at the same time since I've never experienced anything critical or major for many years (knock on wood *knock* *knock* *knock*), I THINK @Jatnieln might be in the same boat, coz after all he's also had his car inspected by several sources.

 

They are all 18x8. The rear has spacers to make them stick out like factory. So my wheels aren’t name brand wheels, I can’t remember what brand they are at the moment, but definitely not anything special.

 

There has to be a solution though. This is a luxury brand car!

 

So I found a shop that does road force balancing. I’m going to go tomorrow to get it checked out.

 

What I mean is you get conditioned to it after a while.

 

Ok...just so I'm not getting confused.
All the rims are 18x8, but the front tires are 225/40/18 and the rear tires are 255/35/18...and they are the original tires the vehicle came with which is a 2015.
And the rear has spacers installed.
Also, the original rims were bent, at least the front from what you mentioned.

I hate to say it, but there are so many variables here I honestly don't think you will find a solution without starting from scratch....which realistically isn't cost effective based on what would need to be done.

Here's my suggestions, and I make them with all intentions of being helpful although it may not seem that way, but honestly you need to eliminate a lot of things before you can actually figure out what the issue is.

1. Get 4 new tires, all the same size 225/40/18 - the reality is the tires you have on the vehicle were on the bent rims, which means they have been subjected to significant impacts which bent the rims, I can't imagine the tires are perfect
2. Make sure all the wheels are road force balanced with the new tires
3. Ditch the spacers until the vibration issue is resolved, then they can be reinstalled
4. Check the runout of all 4 hubs on the car to make sure they are still straight - bent rims could easily mean a bent hub, even though you have no wheel bearing play or noise - repair as necessary if a bent hub is found
5. Road test the vehicle and confirm the vibration is gone...or still there (this is on the assumption that the new wheels are straight and not bent in any way...which the road force balancing should tell you)

To the comments above regarding the GS300...if it is a 300 then that means it's at least 14 years old, since the last GS300 was built in 2006, and built on a completely different platform and way of building vehicles than the IS.
It's not like comparing apples to oranges, it's like comparing apples to giraffes!
It is quite possible the GS does have an issue, even an inherent issue, unfortunately that won't help the situation here.

 

Okay thank you for your help. This is what I’ll do, tomorrow I’ll go get the road force balancing done, there I would find out if I need new tires or not. If I do, I’ll buy them right there. I’ll ask them to check the hubs while I’m at it.

 

Thinking I might do the same later - could you plz report back with their findings?

 

Did you see this thread? Might be interesting. https://www.clublexus.com/forums/gs-...ssue-help.html

 

With vibrations (and most things in life), often times, the simplest and most elegant answer is true. The moment you wrote you had aftermarket wheels, and that your car was a 2015, I assumed at some point someone threw on some sloppy aftermarket parts.

It's either your wheels or tires or a combination of both. You need to start with solid quality OE parts and big name tires. No bunk parts. you say you got the wheels "fixed." Why did they need to be fixed.. and why wheels... plural? More than one? What brand "wheels" did you get fixed? That's your first-no-no right there.

I spent over a decade dignosing vibrations on BMWs. Start with a supreme baseline first then work your way out. On a new car, there's not really anything in "the chassis" that can cause vibrations. Especially not at 70mph+.

I wrote this for the BMW boards a while back but it applies to any car really. Go through this checklist:

http://www.e46mango.com/2017/06/so-y...hakes-huh.html

 

I was on original wheels, I just got brand new wheels Friday. When I bought the car, the wheels (OEM) we’re bent, yes multiple of them. I got them “fixed”, but the problem continued.

 

Hey guys, quick update, I went and got my tires road force balanced today, my god I can’t believe I’m saying this, but it worked out! I finally have a smooth riding Lexus! The previous owner cheaper out on tires, so I’ll be replacing them with Continental Extremecontact DWS 06, but I can happily say my problem is fixed. The tires on the car were the problem, but luckily they were all saved. Thanks for all your help!