Join Date: May 2003
Location: Mountain Brook. AL
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Clincher rims of that era where designed for pressure fit of the tire against the inside of the rim. As Powers says in the '80s a new design was introduced that had a stepoff inside the upper part of the rim wall, and the tires have a corresponding bulge at the edge of the bead. The bulge locks into the stepoff and in theory under inflation pressure locks the tire onto the rim. In practice it is possible to blow the tire off but nowhere near as easily as it used to be. You will have a hard time finding non
lipped bead tires. They are obsolete. If the rim does have the lip inside and is not smooth, then you need to take care assembling the tire to be sure the lip has engaged the rim all the way around, you can roll the tire across the floor for a full revolution pushing down on the tire or just squeeze it into the rim while rotating the wheel by hand (off the bike is easier). Check to make sure the tube is not visible between the edge of the tire and the rim. Inflate slowly looking for signs of tire edge lift off from the rim as the pressure goes above 40-50#, look at both sides of the rim.
This happens to everybody at least once, and when you are up to 80-100# sounds like a gun going off, ruins the tube too....