Know SF has a great offensive line but I think the Rams tackling against them has been poor. It isn't like these runningbacks are breaking tackles because they are Walter Payton either. The Rams are just missing tackles. I am not sure if it is poor angles, or just not being aggressive enough, but it looks like the runningback is stuffed and yet they end up giving up 5-7 yards because the first guy can't bring down the runningback.
It is the biggest problem. That and the Rams offensive line in pass protection.