hey guys, i got some new tires for my 2017 is350 f sport because my two front tires are cupping. ever since the install, my car jolts when it reaches 16-18 miles per hour. The jolt feels almost like a diff bushing is bad and it’s just clunking around. It dosent happen when traction control is turned off so i’ve been gently driving it around with it turned off. the tires are Bridgestone Potenza re980 as all around.(245/40/18 front and 255/35/18) has anyone had this issue and if so how should i go about fixing this?

 

Did you ever have the suspension inspected for the cupping

 

I could be wrong, but I think I remember hearing that prolonged driving on cupped tires can damage suspension components. I would get those inspected.

 

I’m surprised no one has mentioned this, but…
Those tire sizes are incompatible with the Is350.
That front tire is too tall @ 245/40
This means the wheel turns slower relative to the speed of the rears.
That will cause your traction control and Stability control system to error and malfunction like you describe.
If your car is AWD, this will also stress your transfer case and eventually cause damage if driven long enough.
I think the correct front tire is 225/40/18.
That should fix everything.

Verify your tire sizes with what is printed on the drivers side door jamb sticker.