back space help for pitpull tires marshall rims

[randall555]

i just bought 4 42 x 15 x 16 inch pitbull rocker tires and i plan on buying 4 new marshall rims and do a spring over lift . my question is what back space do i need ? the stock rims have a back space of 7 inchs from the plate that bolts to the drum and to the outside of the rim with 34 x 10 x 16 tires . with the stock tires i have only about 1/2 in space between the tire and the steiring arm linkage on the top of the axle . if my new tire is 15 inches wide and i go with a 10 inch wide rim will the tire hit the steiring linkage . if the rim is 10 inches and the tire is 15 inches wouldnt thier be 2 1/2 inches of tire sticking out on each side of the rim and with only 1/2 space to spare wont the tire hit the stering linkage on top the axle . also would going to a 12 inch rim be a good ideal ?

[Jed]

I had 16"x12" rims w/ 6" of backspacing and my 39.5x13.5" tires were never close to hitting any steering parts. 12" rim sure fills out a fat tire nicely. 10" rim keeps the bead on the rim better when aired down though.