If I am using a schrader core removal tool to replace the suspected leaky tire schrader, should I try to position the valve to be at 12 o'clock so that it can come out easily and that you can support the new core using gravity? What happens if the tool loses the grip of the core while it's inside the tool?
You should be able to remove and replace the Schrader valve core without deflating the tire. Put the stem in whatever clocked position is most comfortable for you to insert the new core. I'm right handed, so I'd probably put the stem at 9 o'clock so the stem would be facing my right hand. Use both hands to insert the new core, because the tool WILL NOT support the new core by itself. Use one hand on the tool and one hand to guide the core, guiding the core up into the stem, then turn the tool to tighten the new core in place. Air will be coming out of the tire as you are replacing the core, so refill the tire up to pressure after replacing the core.
