sprung vs unsprung
 

I have a pretty good handle on how sprung weight affects et but no idea of unsprung effects. If weight needs to be added to make class does it make sense to spend big bucks on axles, gears, spools etc.

Re: sprung vs unsprung
 

Yes,But I think your confusing unsrung with rotating weight. By keeping the unsprung weight down you can help the suspension react quicker, and to me rotating weight is more important from a performance standpoint. The farther rotating weight gets from the center axis, the more important it is . I.E. better to have lightweight wheels and tires than gundrilled axles. hope this helps.