Eric Davis has the best Power-Speed# over a 261 game span and it is by a wide margin

The reason why I went with 261 games is that is how many Eric Davis played in 1986-87 when he compiled the best two year Power-Speed#. See Eric Davis has the best two year Power-Speed# and it is by a wide margin.

It occurred to me that Davis might have just happened to have had his best 261 game span over those years and that maybe another player might have done as well or better in their best 261 game span (which might not have been over just 2 calendar years).

In the two year study I found all the guys who had 50+ HRs and 50+ SBs over two year periods by age. So I did that for ages 20-21, 21-22 and so on. I figured that those would be good minimums to insure I found the highest Power-Speed# bracket for each age group.  

But for any 261 game span (using the Stathead Span Finder tool), I had to try many combinations of HR & SB minimums since Power-Speed# is not searchable (also keep in mind that the search results contain many overlapping cases, like June 1-July 1, June 2-July 2, etc.). Over 1986-87, Davis had a Power-Speed# of 85.77 (64 HRs, 130 SBs). So whatever minimums I set would have to get to that number or close to it. Then I would have to do multiple searches, some with high HR minimums & low SB minimums (and vice-versa) as well as intermediate ranges. 

To help me decide what searches to do, I calculated some hypothetical Power-Speed#s ahead of time. For example, 50 HRs & 150 SBs gets a Power-Speed# of 75 (and I wanted to get within 10 of Davis). Knowing this helps set the numbers for the search.

Here is the definition Power-Speed# from Baseball Reference:

"2 x (Home Runs x Stolen Bases)/(Stolen Bases + Home Runs). The harmonic mean of HR and SB. To do well you need a lot of both. Developed by Bill James."

The most HRs in a 261 game span was 118 by Mark McGwire while for SBs Rickey Henderson had 215. Knowing that also helps narrow the range of the search.

No one had 40+ HRs and 160+ SBs. Only Rickey Henderson had 40+ HRs and 150+ SBs. His best PS# was a span of 49-150 (a PS# of 73.87). Far short of Davis' 85.77.

No one had 100+ HRs & 60+ SBs (no one even had 100/50). That would get you a PS# of 75, still well below Davis (who was the only guy to reach 60-100). 

The best 80/50 PS# was 67.6 that belonged to Barry Bonds (81-58).

The most HRs for anyone with 200+ SBs was Henderson with 19. Even if a guy had 40-215, we only get a PS# of 67.45.

In the 45-120 category, Davis and Henderson were the only qualifiers. Henderson's best span there was 50-147, good for a PS# of 74.6.

The highest score in the 65-65 club after Davis is Willie Mays (71-73) for a PS# of 71.99.

In the 50-100 club, Henderson has the highest score outside of Davis (50-147) for a PS# of 74.62. Henderson was the only guy in 40-150 club but his best PS# there was 73.87.

So it looks like no one comes close to the 85.77 that Davis had in 1986-87. But he actually beat that in 261 games from 09-30-1985 to 09-1-1987. He hit 67 HRs with 132 SBs for a PS# of 88.88.