Possible rear suspension issue - unstable at higher speeds

wstar

The car's pretty stable in stock form. I'd go after your list of changes (to suspension setup, tire setup, etc) when trying to diagnose a cause. When you say the rear is "loose", do you mean it's bouncy? Do you mean it loses traction too easy when you give it gas? Does it act like a solid axle instead of IRS? (hoppy accelerating over bumpy pavement?).

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cavemancan

Same brand tires front and rear. Continental Extreme Contact DW

I actually noticed the issue in stock form which is why I am doubting my changes has caused any issues.

I know why it's bouncy but that is not what I mean. It does lose traction to easy but this is not the issue I'm inquiring about either as I would see the traction control light go off when the issue happens. I've never had a solid axle car at highway speeds before but I admit when the issue happens its the first thing that comes to mind. Almost like the mounting points for the solid axle car was loose and the axle is moving side to side.

Above speeds of let's say 50 mph is where it becomes apparent. During lane changes on perfectly smooth surface too. I navigate the car into the next lane the rear just feels loose to the point that when the lane change is over with the tale is still in motion for a split second. Like a split second of oversteer. If I were to put this car on an autocross and go through esses I have no doubt it would be a battle to keep the rear in check.

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