Try this.


http://www.ballreviews.com/Forum/Replies.asp?TopicID=74110&ForumID=16&CategoryID=5
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Spin time is the time required for a (asymmetric) ball to reach it's preferred spin axis (the ball wants to rotate around a particular spot on the surface; that spot would appear to be stationary as the ball spins).  Basically, put the ball on a deTerminator http://morichbowling.com/deTerminator/InfoSheet.htm, turn it on, time how long it takes to stabilize on it's preferred spin axis.

Typically, stronger asymmetry (more mass bias) results in faster spin times.  Less asymmetry gives longer spin times.  A symmetric ball might have a long spin time or no preferred spin axis.  I believe that coverstock preparation can also influence spin times; someone may correct me on this.

SH

You can conclude this from shelley's description: the lower the spin time, the faster the ball gets into its Preffered Spin Axis an the lane, or, the bigger the mass bias influence is on the ball reaction. The mass bias can be exploited to steer the axis movement of the ball towards its final position. A professional ball driller should be able to take advantage of the PSA and its additional influence on ball reaction through pin placement.
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