Spools are a race car item, and are replaced all the time. If weight, or more importantly, moment of inerita are of great importance then aluminum is used, AND thrown away after the event.
Not for street use regardless of material, but certianly not from aluminum. I've used titaninum spools before. <img src="/forums/images/graemlins/kewl.gif" alt="" />
Kary

1987 Mitsubishi Pajero "Modified"
The other original Mitsu brother
Northwest Trailmaster