is it possible to fit 20x10 1 piece rim on an 03 sedan lowered on tein s-tech without modification?

 

There aren't many 1 piece wheels that come in 20x10 with a high enough offset to avoid rubbing. You might be able to get away with it since the s-tech drops the car a decent amount, thus could induce a good amount of negative camber.

 

You'll need atleast a mild fender roll even with a +50 offset on the wheel, assuming you're going to run the standard 275/30/20 tire.
-GP-

 

+1

But with a fender roll you can fit up to a +40. I've had three sets of 10" rears on my sedan over the last year.

 

Or a +25 if you wanna stretch the tire and run 2 degrees of negative camber That was just for you Tim, i know how much you loooooove stretched tires and neg. camber!
-GP-

 

I'm still waiting to see you pull off a +25 10" with a 255 and all that camber!