Steve is correct. There is no tube flaw or tube property that makes it more or 
less likely to blow a tire off the rim. It is completely the job of the tire to 
hold the tube in. Think about tubeless. The only job for the tube is to be 
airtight. Blowing the tire off the rim means one of three things

1. Over inflation. In my opinion 69psi is insanely high for a 50mm wide tire.  
I'd think 30 would be about the highest I'd go at that width.  Did you go to 60 
in the cold garage because that's the max and then carry it to your warm house? 
 Do you trust your gauge. My floorpump gauge understates pressure by about 20 
psi.  If I used my floorpump to pump a tire to 60 on its gauge and then took it 
inside, in about 30 minutes it would really be 90psi. 
2. The rim/tire interface failed because of some flaw. I've seen the rim tape 
shifted up into the rim hook. I've seen mold errors where the tire bead is 
flattened. An undersized rim or oversized tire would also contribute ( but not 
in this case)
3.  Installation flaws. 

Bill Lindsay
El Cerrito CA

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