Originally Posted by
Henry III
I always thought SLX was used on larger size frames since it was more rigid with the rifling. I thought SLX was also heavier then SL from the scanned chart I've read online. I've never rode a SLX frame though so I don't have much to add to this discussion.
You're right about the increase in weight and rigidity due to the rifling in SLX (and in SPX). The choice to use that rigidity to flex less under higher weight is available to the frame builder, as is the choice to use SP instead of SL. It's up to the builder. Probably SLX will not quite feel the same as SP.
Just looking at vintage high-performance frames over the years but without say, Randy Jawa's in-depth experience, I usually think SLX was chosen for road and SP chosen for track, to give more rigidity and better power transfer to the sprinting track rider rather than to the rouleur or randonneur keeping it going quickly for another 50 miles. SP was also chosen for touring frames to handle higher weight. Obviously, many great touring frames were made with lighter tubes as well, such as 531 rather than 531ST. Example is the Trek 720 from the early and mid-80s.