What angle should I set the VTA on my VPI turntable?

lewm,
You must include a pivot in your analogies or they don't apply.  Imagine raising the pivot point until the stylus lifts from the platter.  The arm will balance at less than vertical.  That's because the leverage at the cartridge decreased as the cartridge neared the gravity line and equilibrium was reached (balance).  The VTF is then zero.  It must have decreased.

lewm

... The question then was not "whether" VTF goes up when the pivot point is raised, but "how much" does it go up. Someone did the experiment, and the answer was "not very much", but definitely VTF went UP.

Yes, it goes up, and it's easily measured with a stylus force gauge.

Funny, my experience is the opposite.  I wonder if the answer flip flops depending on which side of parallel the tonearm is.  Above, below or horizontal.  I know what my arm as it's set up does.  Physics isn't my thing and there could be (and most likely are) other explanations I've not considered.  I would love an answer from someone who actually knows.  No one here does, including me.  It's fun and didn't get too sideways.  Cheers!

Thanks guys.  If jcarr catches this thread, maybe he can weigh in with some practical advice since I am using one of his cartridges (Lyra Kleos).  

My sense is that lewm's approach makes the most sense.  I ordered a cheap super light/small bubble-level to double-check the azimuth and VTA one more time.  I will probably tweak the tuchus (the backside) of the arm up a smidge and call it a day.   

While I can envision that raising or lowering the tail of the tonearm will affect VTF and the P-S distance to some degree, I surmise that a small adjustment of the VTA wouldn't make all that much difference in SQ.  I am not OCD about my turntable and do not have the patience to make a minute adjustment to VTA and then readjust the P-S distance and VTF.     

Hello,
Not even close to an expert here. Here is my two cents. Please do a final VTA adjustment after about 50 hours or per Michael Fremer set it to 93* when the cart is new. As the cart breaks in or settles you will lose about 1*. I think the angle is 92.3*. After a lot of playing you will naturally get to this. Or set it to 92* at the beginning and recalibrate after 50 hours. Regardless once set up I would do a listening setup. That’s what I did when setting up the Prime with the unipivot arm.