Fifteen forged ZK60A-T5 magnesium wheels and four forged 2014-T6 aluminum wheels were roll tested at the Wright-Patterson Air Force Base in a cooperative wheel-test program with The Dow Metal Products Co. Magnesium wheels were modified F104 wheels which were redesigned to reduce roll life from over 1000 miles to about 100 miles at a load of 10,000 1b. A load versus roll-life scatter band was established by testing 12 magnesium wheels at loads ranging from 6500 to 12,500 lb. Three aluminum wheels, which were thinner but still 20 per cent heavier than the magnesium wheels, had roll lives comparable to the magnesium wheels; it is concluded that a magnesium wheel can be about 20 per cent lighter than an aluminum wheel and have the same life expectancy. Strain was measured at various locations in wheels being roll tested, and the variation with tire inflation pressure and rolling load was determined. The site of fatigue crack initiation (bead-seat radius) is strained well into the plastic range under normal roll test conditions. Wheel roll lives and strains measured at the bead-seat radius were found to depend upon the ply rating of the tire mounted on the wheels and also upon whether tubes were used in the tires.