Lowering on stock suspension arms?
 

Looking to get coilovers and wondering how low can a s13 be lowered before aftermarket arms like rucas and toe arms are needed to adjust the alignment to stock specs?

not far once your low like you would like you DEF need arms all around

I'm pretty low and I think I'm at -3 degrees camber in the rear and -1 in the front. That's all stock arms and just coilovers. Never adjusted the camber or anything. Just toe when I got an alignment like a year ago. I'm on 18s too

most coils will have a camber adjustment on the fronts(this only adjust how much tire contacts thw ground) but the rears your SOL, best thing to due when lowering a car is to get an alignment...you can slam any car you want all day without getting an alignment, its not recommended at all but you can. You posted this so it shows you have a concern about this subject, look it up lots of suspension talk around the webs, do it right youll do it once untill it breaks from NORMAL wear and tear

rear end toe will be bad bad bad burn tires out weekly when your low