Im lookin to space my wheels out abit but ive got 16" audi alloys (on the car wen i bought it) and wonderd wot mm is safest to use ??

Will all depend on the width, ET and Tyres.

im running 30mm looking to go 38mm on the rear possibly 40mm

never had any probs with the 20mms it had

Wer they bolt on hub spacers ?? I was jus looking at shims either 3mm or 5mm...

Never used bolt on hub spacers befor

15mm hubcentric (like Eibach prokit ones) per wheel, with longer bolts to suit, will be generally fine on most applications.

my 20s used longer nuts and i fitted an extr5a 5mm no problems what sio ever then got hubcentrics 5,10 mm on standrd bolts will be fine if i remember correctly as long as you can get 3\4 full turns that enuf but any more than 10mm id rather use longer bols to be safe

Thanks guys i was only looking to go out by 10/15mm max... well after i get it lowerd and thats a new can of worms to be opened later ha!