HI Everyone i bought Lexus SC430 and am finding this weird thing whenever it hits a bumpy road wheel losses control and go right and left without much of my control. Does anyone has this problem with SC430 2003?

 

Start checking front end parts. Front shocks, upper and lower control arm bushes, upper and lower ball joints, inner and outer tie rods, steering rack bushes. It is common for these front end parts to be worn. You could look into figs bushes. Most on here have done wholesale change on the front end to tighten every thing up. The geometry of the steering rack to the knuckle gives it a propensity to want to bump steer. So even slightly worn front end parts make it feel this way.

 

My 2005 with donz 20 " rims 10 on back 8.5 on front I have sway bar front and back . If I hit a bump the car steering behaves like yours I have not done any other suspension mods because my car has now 7650 miles and its a 2005

I did notice same condition when I had stock oem runflats The 20 " rims do ride better then the run flats.

 

I have a 2002 and my car does the same thing aND feels like the steering wheel is loose highway speeds also this is completely stock no modifications except for front and rear rotors that are slotted and cross-drilled I've been reading on other forums they are saying the lower control arm for some reason sometimes Bend without notice and most of the bushings go bad Also if anyone knows a good strut and sway bar upgrade let me know please and I've been thinking about BC coilovers

 

Same here. When I asked about it here before, I was told to look at the bushings on the anti-sway bars and perhaps consider an upgrades.

 

Front strut bar makes a big difference when operating with top down