I have a new 2003 SC 430 (1400 miles) with run flat tires. When I bought the car, I had the dealer install Momo wheels. I have been very dissatisfied with the handling of the car at highway speeds (50 – 60mph). It feels “squirrelly”, not stable. Maybe I am saying it handles too well but it feels “twitchy". Finally I had the dealer put the original equipment wheels back on the car and that helped but there is still a distinct vibration. My radar detector vibrates; I can feel it in the steering wheel and in the seat. Now I am wondering if the problem is the run flat tires? Have people been happier with the “old fashioned” regular low profile tires? I had a 1996 SC 400 and it felt stable and solid like a freight train on the highway. Has anyone else experienced this? Is it the tires or just the way that this car is set up?

 

There's definitely something wrong with the car.
Maybe the suspension is bent either in one of the control arms or tie rod.
My guess is a bent tie rod, that would give it a squrilley feel.

The car might be new, but when they get delivered to some dealers (being driving by car jockey's either from the port or the bigger dealers) they get beat on, maybe the guy went off a curb or soemthing.
Deifinetley jack up the car and check for damage.
I rode in a SC430
It was ROCK SOLID like my SC300.

 

The crappy handling and ride comfort is 100% run-flat tires. They are really horrible tires, but most people will opt for them because it's an "option" and seems like a smart one. You should ditch them for some regular all-season performance tires. Don't forget to have your wheels balanced too, it's only like $40.

 

ohh, they have been balanced, about four times in three weeks... (by the way this post was made by my dad... not to cause any confusion-Im driving his 1996 now...) Im pretty sure its the run flats also...

 

I don't know anything about run-flat tires, but I do know that tires with grooved tread will sometimes "tram" on the grooves on a freeway, which results in an odd feel to the handling where the car seems to shift the track on its own. I get a bit of this with my Dunlops but I'm used to it.

Ral

 

make sure your alignment is correct and make sure your suspension is not screwed up too...

 

A similar question was asked by someone writing to road and track this month

oops I read it too fast and it was a GS430 not a SC430.

 

here it is anyways

 

This is hearsay;

from a guy who has ZERO technical skills whatsoever, but he is quite tight a big Lexus dealer in the UK, he tells me they quietly drop the rear axle on SC430's to carry out modifications in order to correct handling issues - they only do this if the customer has complained about the handling.

Could be a load of bollox - could be true as the SC430 has been subjected to many bad reviews regarding the handling & ride.

 

I had experienced some vibrations when I first mounted new tires. It was pretty annoying and I thought the tire technician screwed up. But after a few thousand miles when the tires wore in the vibration went away. Thus I doubt that your new sc430 is the problem here but the new tires, especially those flat-run tires with the side walls.

 

he changed out his run flats for a some micheline pilots...vibration still there, its not the tires, I think its something with the steering...