Old 12-23-20, 04:40 PM
  #15  
Carbonfiberboy 
just another gosling
 
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Bikes: CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004

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Originally Posted by wtandem
I am pretty sure our tire from the original post did not blow off. It was still well on the rim when we stopped. He is a picture of our failure, a very similar spot to the picture you are referencing, although not nearly as large.
Right, even more interesting. Your tire has that same fabric showing right above the bead as the blown-off tire has. I went out and deflated our 28mm 5000 which we've had on the front for several months, enough to wear the flashing off and start to develop a flat in the center. The area right above the bead looks just like that same area does on my in-the-box 5000 tires. If you have any others, you should take a look at them, see what that area looks like on them.

I wonder if it's the 90 psi? The official pressure range for a 25 is 95-123 psi. Back when I ran 25mm, I ran them at 115 Should have used 120, but that was just too harsh. I wonder if running them under-inflated and under much heavier than usual load, caused them to move a tiny bit at the bead and saw away at that area until the rim went through. That's what it looks like.

I'm running my 28mm 5000 on the front, which measures 29mm inflated on my rim, at 105psi. I run 32mm tires on our tandem at 95 lbs. 282 lb. team, 36 lb. bike. My rule of thumb for our tandem is tire pressure = 3000/(measured tire width). Because of tandem frame design and the usual proportion of captain-stoker weight, tire pressures on both ends are usually the same, unlike a single.
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