Just a guess... I believe that the sound will go away if you remove your saddle and grease the contact sections between the rails and post craddle. The combination of certain seat rail materials mixed with certain posts makes a small tinkle noise until greased and re-tightened. My guess is that you have a ti railed saddle with either a thompson post or Trek propprietary post, i.e. Bontrager or Icon. Anyways, try my fix and see if this is the case. Good luck.
Kevin Weitzel Phoenix, AZ
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