dang - welded in 3/16 spacer ring on wheels and still the brakes pulsate

i have 3 stock rims and 4 of these aftermarkets but the only combo that works without any pulsating is the 2 aftermarkets on the back (with the spacers welded in) and the 2 stockers in front. for the life of me i cannot figure why this is such a PITA!