8 3/4 housing U-bolt torque

I know that if you overtorque the u bolts you can dent/ distort the axle tubes.
I figured that was the reason for the relatively low torque spec. I never quite understood how over-tightening the u-bolts would make for a rough ride. To me, there'd only be two way- either it makes the spring bind, or it increases the spring rate. I just don't see how either of those could happen.