Originally Posted by Camilo

i have a very cheap crank and square taper botom bracket on one of my bikes. i'm not a particularly strong rider, but notice the chain rubbing on the front der. some times when I really put everything I have into it while on the big ring. Can't say if it's the arms, rings or BB spindle that are flexing. Plus I can't say it affects 'efficiency' at all. But it's true, my other 'decent' cranks (Tiagara, Deore level and above) with modern-er BBs never do this.