Ok, im not mechanic, but i know something is wrong.

my 02 is300 is still pretty much stock (see sig).

i recently just had to change both back tires because they suddenly had bubbles in them and no i dont hit bumps.

ever since then, ive noticed my ride on the freeway it doesnt hug the road very well anymore. it seems like the front wants to keep swaying left and right. it feels as if there's a lot of wind and it's blowing me around in my lane, if you can imagine.

what the hell is that? is it my suspension? do i need an alignment or something?

please advise, thanks.

 

Did you buy the same tire brand?
Is the tire spec the same?
How much tread is on the front vs. rear?

If tire brand isnt the same, that could be part of it. Not every tire is made to be exactly the same as the next tire/brand.
Im sure the tire specs are the same.

Change out the fronts to the rears, and see if that changes anything.

 

i had a similar issue on my es300 with 18" enkei wheels. come to find out when they changed out my 2 tires that were worn, the alignment was fubar's and thats why my car felt like it was all over the place. i guess during alignment if the guy knows what he doing he can adjust the toe-in and the vehicle will want to go straight than turning so quick. just an idea

 

the 2 brand new tires in the rear are the same specs, but are now federals.
the 2 front i believe are 2 different brands, one being toyo and i forget the other one, but they are the ones my car came with when i bought it and it was smooth before.

so, if changing the rear tires by simply taking the old ones off and throwing the new ones on, that can change my alignment in the rear???

or do i need to go ahead and change the 2 front ones to federals as well? the 2 in the front are still good as far as tread.

 

The Federals are smaller than the Toyo for sure. Just dont try to turn hard on slippery road. Your back end will slide a little.
Smaller tire in the front is a better idea on any FWD and RWD cars.

I would do the alignment first, since that would save you money.