just wonder who has used what in terms of spacer. so far it looks like im going to end up with a ~.5-.6" spacer. (already have longer studs). would just like to see what others are doing there.

 

If the Et is about 58mm or so you dont need any spacers in the rear with a 4:th gen axle

 

56mm

and it being up against the wheel well says otherwise. unless my car is lying to me..

 

That sure is strange. I have got the C5 magnesium Wheels on my car and the ET in the rear for those I Think is 65 and they only did hit the bumpstop, which I trimmed a bit of with a grinder. Still running 275/40 on those too and no issues..Now I´ve bought 2, 8mm spacers to put in the rear just to get them out more, mostly for the looks of it :-)

 

I think some of the Y2Ks are 9.5 and others are 10.5. I have mine (10.5) on a 4th gen rear and they're very close to the forward edge of the wheel well (near the pinch weld, that could be trimmed). I don't think I would need more than 1/4" right now, but I only have 275 wheels mounted. 305s may need a bit more space or some trimming.

 

I just put 285/35/18 in a 18x9.5 c5 speedline and i had to beat the front part of the rear fender inside, and then i got 1/4 spacers to be extra safe. no bump stop rubbing that i can confirm of yet.

 

I also have a 4th gen rear.