tcho82

iTrader: (1)

Tried to search but couldn't find anything similar. I just replaced all four shocks with KYB gas a just shocks, and replaced the two front boots as well. The car seems fine overall on smooth roads, but when I'm on the freeway, and going over a rougher patch of road, 60 mph+, the rear seems a bit unstable, and seems to "shimmy" a bit. I'm not sure if this is normal. I don't recall the car ever feeling like this. I have not gotten an alignment yet, but overall the car seems to drive true, I can't imagine the alignment being so off that its causing the car to feel this way. This also occurs on surface streets going 45+ and going over rough patches. Any thoughts are appreciated.

Aspect

Try to get your alignment done first so we can eliminate that as a possibility. Even if it "seems" to drive fine, it definitely is out of alignment which could be a factor. Also, KYB Gas-a-just shocks aren't OEM shocks(pretty sure Tokiko makes the OEM stuff) so they would definitely feel different. Probably also a good idea to check all your nuts and bolts again.

Gville350

iTrader: (10)

Try lowering your tire air pressures to see if that helps.

tcho82

iTrader: (1)

Thanks for the suggestions, I'm going to try to get an alignment this weekend.

erichuang

So, just curious, any updates? Are the KYB Gas-a-just shocks good replacement? thanks!

My New Lex

I know this is a really old post but I am having the same issues after changing all four shocks. I changed out my oem shocks (120, 000miles) to f-sport. At first I was thinking the new f-sport shocks (stock springs) were just super stiff causing the unstable or loose steering feel over the rough roads (exactly what the OP was reporting), but I am starting to feel like there is something wrong. I recently drove my cousins IS 250 sport edition and it just brought me back to how my car used to feel, which is leading me to think something is wrong or loose with the suspension. The steer bump on bad roads has always been bad, but after the new shocks it has gotten to the point of being unsafe.

Hoping someone has some idea, updates, or anything I should try? (I have already tried getting an alignment and plus my mechanic did a visual inspection under the car with no luck). THANKS!
-Michael

jr4div2

The stock lower control arm bushings are crap and cause the front wheels to jump all over the place. I suspect now that the f-sport shocks have stiffened up the suspension, the LCA bushings are being deflected more than before. You should look in the the RR Racing LCA bushings. I too had stock suspension on my 250C and hated the way it felt on grooved/bumpy roads. I felt like it was jumping all over the place and had to do too much steering correction. Turns out, it indeed was with the way the extremely soft stock LCA bushings are. I installed the USRS from RR Racing and wow!!!, what a difference. Fact is, I had BC Racing coil overs and f-sport front and rear sway bars installed at the same time and it feels like a sports car should feel now.

My New Lex

Hey jr4div2 did it feel like the front wheels were skipping over the rough roads and bumps??? That's how I've been feeling with these new shocks.

​​​​​​Another weird thing is that I haven't read anyone on clublexus complaining about how stiff the f sports shocks are even after the break in period. Maybe something my mechanic messed up on...I highly doubt it though.

Yeah I was thinking of picking up a set of the USRS bushings soon, but I am just worried it wouldn't fix the problem and end up making it worst. I always wanted to upgrade the LCA bushings, guess this will just be another excuse to order a set now!

jr4div2

That is exactly how it felt. Scared my wife so bad, she wouldn't drive it. Now with the BCR's and USRS, things are a bit siffer and there
s's more NVH, but that's what you get when you want to feel the road and not ride around on the pillows that Lexus put's on these cars.

LexoDAV

you can visually inspect the from LCA bushing to see if it's torn/cracked. The front LCA should be unrelated. It sometime can be the surface of the road your on. It happens to people all the time. I would pay more attention to rear suspension bushings. I'm not knocking on RR LCA bushing I want a set too but for drivability issues getting a stiffer durometer
bushings won't hold the road any straighter

LexoDAV

👍 lift the car up high so you can inspect each part one by one. Get a heavy duty pry bar or screwdriver and press side to side to look for any broken rubber bushings

jr4div2

Sorry to be contrary to that statement. Have you seen the video that RRR did comparing the stock bushings to their harder durometer bushings? You should and then you'll know what you stated about holding an straighter is simply not the case. I for one do have them on my IS and the steering and wonder (following uneven surfaces, bump steering on the interstate) that I was experiencing is practically gone. If you don't have the experience of before and after, please don't make false statements.

My New Lex

Wow! After installing the USRS from RR racing, it really makes the car feel stable over bumps and during braking! I think this really fixes that unstable feeling over rough roads or bump steer (what some people call it, I think??)!
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The only con about the USRS is how stiff it makes the car feel. When hitting the lane reflector bumps or pot holes, it makes the whole car shake really bad. Hopefully there is so kind of break in period or some getting used to. If not I might have to remove these and get the RC-F bushings, which I've read somewhere on here that it is stiffer. Someone correct me if I am wrong...

Thanks for all the reply!
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Gville350

iTrader: (10)

^Yes, there is a break-in period. Mine have definitely loosened up over the months.