minimum clearance to springs?

I run the same width rim with 4.25 BS and 275x60x15 555R Nitto drag radials. I tried 4.5 but I didn't feel to good with the clearance


i looked at a few different vendors for the wheels i bought (US mags 101, slots) it looked like the same wheels with 4.5 inches of backspacing and 4.25 inches of backspacing had the same partnumber, so even though i hoped for 4.25 but such is life

i should get my new drums in today, and with them on and everything torqued down i can get a proper measurement but it looks like i have 3/16th now

if that remains, i can add a 3/16th spacer to it and i should be good...or should i go with 5/16th just to be safe ?
or, would 5/16th not leave enough threads on the studs to properly tighten the lugnuts?

(these are the stocker 7/16th lugs)


THANKS GUYS