Tweetcheck the rim and tire size of the spare...is it smaller than the others? or larger? it didnt pull right after, correct? get the old tire changed out with a new one asap..it's gotta be rim size (witch can couse big prob's for ya) if it didnt pull after it happened. if it did pull, could be ball joints, tie rod's, or front end allignment.
oh, and it being a diff. tire has me wondering if it's even the same tire size...