Originally Posted by T-Mar

The best way to determine a PX10 versus a stock PY10 frame of this era is via the seat post diameter. The PY10 used the standard metric Reynolds 531 tubeset which had a seat tube with an internal diameter of 26.6mm and typically fitted with a 26.4mm post. The PY10 used the lighter gauge Reynolds 531SL tubeset which used a seat tube with a 27.0mm inner diameter and typically fitted with a 26.8mm post.