Can anyone tell me what kind of clearance issues (if any) needed to be addressed when lowering an LS with 20's? not sure on the tire size off hand.
Thanks

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He has this done, and IIRC he trimmed the wheel well cover.

No major issues as long as you stay with a high offset wheel. Mine rubbed slightly in the back with a few passengers and moderate bumps.

I have the Eibach kit and 20's. I trimmed the front and rear inner fender covers and just recently rolled the rear fender lip as much as possible. After my kit settled I had a drop of 1.83" which was well above the 1.1" that Eibach claimed. I had engineers from Eibach (Helps to work at one of the biggest Eibach wholesellers in the country) come in and check my suspension to make sure I was not wrong in my measurements. They confirmed the drop.

After the "Adjustments" to the car I do not rub unless I have a full load of people in the car, and then it is only very minor over dips at higher speeds (65+).

Hope that helps.