safe size spacer?

  1. #1
    iv got some spacers and long bolts laying around that i was thinking of using on my car just to bring the rear wheels out a bit, iv got i think 5mm 10mm 15mm spacers. now there not the hubcentric ones theyre the ones that are held on with long bolts, i know its not really safe to use any of these, but whats the max i can use?

    thanks