What is the difference between a sprung an unsprung hub? I tried to search around, but I can't seem to dig anything up.

 

bump

 

That's a picture of a Saab clutch but the idea is the same. There's springs between the friction disk & it's hub. It gives some torsional flex so the hub can turn a little bit against the disk, compressing the springs.

 

so an unsprung hub will be a lot harsher, but ultimately will transmit the power better.