Jeremy, I am a 71 year old golfer, and I use a Titleist 910 D2 driver with a Bassara 50 shaft.

Initially, I bought the driver new with a 10.5 degree loft and a regular flex shaft.  Last year, I had by pro order the same shaft in senior flex.  

I experimented with both shafts and drew these conclusions.  

As you would expect, the higher the loft, the higher the trajectory, but distance depends upon your club head speed.  At my 85 MPH club head speed, I get more 5 yards more distance at 11.25 degree loft than I do at 10.5 degree loft.  But, at 12 degrees, I am 10 yards shorter than at 11.25 degrees.  

Also, at first, I thought that the senior flex gave me more control over direction since the regular flex caused a fade.  But I worked with my pro over the winter, and I am now back to a regular flex for straighter drives.

So, in my experience, flex controls direction and loft controls trajectory. So if you have improved your swing and want lower trajectory, lower your loft to 11.25 or 10.5.

But, here is the thing that I found about trajectory and distance and, once again, it is all about club head speed.  On my irons I have low trajectory shafts, Tru Temper Dynamic Gold.  But I recently experimented with a high trajectory shaft, Tru Temper XP95, and immediately picked up yardage ranging from 10 to 15 yards on my long irons, 8 to 10 yards on my mid irons, and 5 to 8 yards on my short irons.

So, if you are older and/or have a slower club head speed, look for high trajectory shafts to give the ball more "hang time" up in the air.  That will gain yardage much more than loft and much more than flex on all of your clubs, not only the driver.

Rich

A good question that hopefully someone with more technical knowledge than I have can answer.  But its not just the shaft flex that matters as they vary among manufacturers.  In addition, modern shafts have many other characteristics that affect performance (e.g., low or high kick point).  If you can, I'd suggest finding a Titleist fitter in your area and trying a number of new shafts and see how they perform.  Thanks.  J.A.C.

I'm looking to match ap1 irons with the proper shaft. I purchased an ap1 #8 with the stock XP95 300R shaft. I love the heads and hit them well. But I believe I could improvve greatly with the correct shaft. have a cally #8 RazorX with an Aflex mid torque low kick 65 gram shaft that hit very well. What shaft would Titleist suggest for a set of AP1 irons? Any thought or ideas appreciated.

My original AP1s had GD 65 A flex but got too hippy.  Kuro Kage has 65 and 85 g graphite option.  It came down to the KK 85 and the XP 95.  The fitter liked the KK in longer irons.  The 65g is the usual floor model in graphite for the AP1.

Thanks Don,