You need some kind of lubricant between the head and the bowl of your timpani, otherwise the friction from pedaling will create physical "stickiness" and audible pops.
Teflon tape does a wonderful job of eliminating these problems. Simply apply it directly to the bearing edge of the bowl. If done carefully, you'll never have to reapply lubricant again!
This version of Teflon tape is much thicker than the kind used for plumbing purposes, so it won't degrade over time from the force of the head. This pack comes with 36 yards of film, enough for multiple sets.
