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I have a couple questions.
1) The black piece that holds them in place fell out when I aired up. I didn't think anything of it and went for a 50 miles ride and hit some high speeds. All is well but not I read that that piece is vital to the safety of the stem. Should the come off that easily? Are they easy to put back on?
2) When i added air it was hard to get the hose to seat because they flexed when i pushed the nozzle onto them. How do you guys air up without pushing the stem hard, therefore bending the stem?
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The black piece simply snaps into piece on the rim. Perhaps its was bumped loose during the tire change. They should be easy to snap back into place. If they don't snap into place easily then they are broken.
Holding the stem from behind while airing is the correct method. The support is needed notonly when you are airing them up but also when you're checking the pressure with a tire gauge. That need is relived with an all metal stem.
As to the sudden fear, the OEM stems under many, many circumstances have performed well until they get older and more brittle. The presence of the stem support is essential. It's not so much that the OEM's are just bound to fail at any moment, but that they have a weakness that some of us are unwilling to risk. That will seem odd coming from me because more than one member will quote me as saying, "Friends don't let friends ride on OEM valve stems." I do think you should replace them, but if you get the support back into place the next tire change should be adequate.
Put the supports back into place and ride that beast.