Originally Posted by
Scooper
My 1987 62cm Paramount was built with an SP down tube and SL top tube and seat tube. This was a common tube mix for 58cm and larger frames when SLX was considered too flexy for larger frames/heavier riders, and SPX was considered too heavy. SLX was used for frame sizes 57cm and smaller.
This is the decal Schwinn put on my SL/SP frame.
Thanks for decal info. And the description of SL/SP on larger frame gibes with my understanding. As I understand it, SLX and SPX are identifical to, respectively, SL and SP from a metallurgy and thickness standpoint but the X references ribbing added to tube ends to increase stiffness. So SP not as flexy as SLX because its thicker walled, but not as heavy as SPX because no ribs.