wednesday evening, after having to accept a ride home from a co-worker while "fixing" a flat on the side of the road, i decided to go out and buy some forte kevlar road tires. rode them thurday to work and back, no problems. rode in to work today, parked the bike in my office, and went to my all day meeting. when i return to my bike, i see the front tires part of the way off, and there's about an eight inch slice on the rim side of the tube. wtf?
so i get out my new crank bros speedlever, and within minutes I've got the new tube on.
i use the compressor at work, 60psi, everything looks ok, no bulges, 80 psi everything looks ok.
i go to put the chuck back on the valve for one last burst when, POW!
the tube blows inches for my left ear.
scared the ***** out of me, my left ear is still ringing, i feel like i am wearing ear plugs, can't hear for nothing....

ohhhhh!!!! that sucks sorry so much. Maybe other users can help me I think you would need to have booted your tire first with a dollar bill or other material

there was no hole or anything in the tire, it was just off the rim

You may be getting the tube trapped between the rim and the edge of the tire. That prevents the tire's bead from seating properly under the rim's "hook" edge, AND puts the tube where it'll be trying to heave the unsecured bead over the edge of the rim too.

To prevent that, after getting the tire and tube onto the rim, squeeze the tire together so you can see down into the rim bed. You shouldn't see the tube at all. If you DO see the tube, knead and work the tire & tube with your fingers to coax the tube up into the tire casing where it belongs.

Another "gotcha" is when the thick rubber base of the valve is down in the bed of the rim. It can keep the tire's beads from getting under the hooks, too. To prevent that, after getting the tire & tube onto the rim, push the valve up into the rim so the base is definitely up in the tire, not down hogging space in the rim bed.

Lastly, pay attention to the bead line on the tire. Give the tire 30 PSI, then take the pump off and spin the wheel while watching the bead line on each side of the tire. Does it have high spots? Does it have spots where it ducks out of sight below the edge of the rim? Let the pressure down to "very squishy," pinch it, look for the tube being where it doesn't belong, then even up the seating with your hands and try going back up to 30 PSI. Then 60 PSI. Still evenly seated? Keep going.

thanks, mechBgon, i'll check all of those next time.
after a little time to cool off, and some chicken dinner, i've accepted the fact that the second blow out was most likely my fault. i was in a hurry, i'm sure i missed something.
but i can't get my head around how that big slice happened. if it blew out, someone would have heard it, my office is inside the warehouse, right next to the warehouse supervisors office. it was fine when i parked it there. how does a huge gash like that just suddenly appear?

When the tire comes off the rim, the tube blows up. That's basically how the huge gash appears.

at first I was reading this as someone sliced your tires. Glad to hear that's not the case.

I usually inflate to 5 psi, then 20 psi, then 40, checking to make sure the bead of the tire is seated evenly each increment. Once I've hit 40 and it looks good, I feel pretty safe about inflating the rest of the way.
I've had 2 pinch-flats while changing a tire: both from not being as careful as I should have with the tire levers while putting on a new tire that was really tight.

how long until the ringing stops?

mechBgon gives excellent advice. I also suggest working with a bike friend if you have one to check on your technique. You'll be an expert before you know it!

Two other tips: I slightly inflate the tube (just till it has some shape) before stuffing it into the tire; it seems to help hold it up inside the tire and decrease the chance of a hole from a level/rim contact. You may need to let a little out to get the last bit on tire on the rim.

The other tip is to try to mount the tire without using any levers. I know that is very hard with a too-tight tire, but I have found most tires can be mounted by slowly going around the rim, pushing the tire over the rim with your thumbs. Make sure the rest of the tire is down inside the rim, not up and seated against the rim bead. Hope this makes sense--time for more coffee.

For me it took a couple of hours. When this happened to me a few years ago, I thought someone had walked up behind me and pulled a trigger.

Reminds me (sorry for the tangent) of when I asked a coworker how long it took before the ache went away after a vasectomy. Without a blink he said, "Oh it never goes away. You just get used to constantly feeling like someone kicked you in the groin."

On a bike that I no longer have, I had a situation where the tube kept pushing out around the edge of the tire and popping. As I recall, the wheel had taken a bit of a beating over the years and I finally had to solve that problem by getting a new wheel with nice new rims to hold the tire in place. So, if you are riding a beater, that could be something to check.

As someone considering a vasectomy, please tell me either a) that was a botched procedure, or b) he was kidding...