15 inch small bolt Rallye Wheels???????

what size tire are you running on your 14 X 5.5 rallys i am going to do the same as far as 15 X 8"'s on the rear with 255 X 60's but if the 275's will work would be much better, do you have any problem with the back space on the 8's and how much back space are they on the 8's THANKS ---SLO-MOTION .............