OK, I'm embarrassed to admit it, but I don't know much about replacing valve cores on Presta valves. I have tried a search here but not found the exact answer to my questions.
This morning when I was trying to air up the rear tire on my commuter bike the valve core came out with the pump; after trying hurriedly to fix it I finally had to give up and just drove to work. This has happened to me before -- I've had messed up valve cores on perfectly good tubes but ended up changing the entire tube because I didn't have extra valve cores.
I now have a 10-pack of extra cores on order and on their way to me....
1. Generally, when one is having a problem w/these valve cores, are they defective, or just not properly seated?
2. I ordered a tool for replacing them (why not), but is the tool really necessary? Can I just fasten these in w/something else in my toolbox?
3. Anything else I need to know? I feel like it's a waste to throw away good tubes if the only problem is a loose or defective core...