I started focusing on ball speed, too much, and ended up causing myself more problems than I was ready to
deal with.
Based on the balls I throw, how they are drilled and the surface, along with my rev rate (which i haven't taken the time to messure), I carry best when my ball speed (at the pins) stays around 15 to 15.5mph
When the ball speed drops below 15, I start leaving weaks 7's from hitting the 1-2 pocket flat. Or, I leave weak 10's from hitting the 1-2 pocket light.
If my ball seed starts increasing above 15mph, I am ok till I go over 16mph, then I start leaving a lot of solid 7's, 9's and ocassional 8's