Originally Posted by
dahut
I have a similar unit, but mine has a tank, with a 3 gallon capacity. It works fine, too.
I think you may be on to something, though - pressurize it to 90psi with the compressor and hit it a few final licks on the manual pump to get to 100 psi.
Now, I dont go too much by absolute pressures and rarely actually measure the fill... I go by feel and I take it slow. The reasons why are explained above.
But, I'm guessing you are following manufacturers recommendations for the tire and/or bike, and want to be precise?
PS - What I do is just "air it up," a little at a time, until the tires are really hard or haven't popped/herniated, etc. Then I test 'em on the road. If it feels like it aint right, I air it up some more. Repeat as necessary. I'll use a tire guage if I have any doubts... and if I can find one around the shop.
(It aint scientific I know, but thass' kinda how we do things in my part of the South 
)
I don't have the 'feel' yet. I just pumped it up with the frame pump until I couldn't push the tire in 'too much' with my thumb.
The bike road fine to me, but if it calls for more pressure and it will roll easier that way then adding more pressure seems smart.
The Bontrager sidewall states 'inflate to 100 psi'. So I thought I should at least try to come close. My last road bike (el cheapo) stated, 40-65psi. So I had a range to go by there.
still, I have no idea what 100 psi feels like so I cant go by that. Just trying to set everything up the right way.