I've got one of those tire/rim combinations that are very difficult to mount. Tire= Continental Grand Prix 4000, 700 x 25. Today I was headed along at ~23MPH and the rear tire blew-- pop! -- off the rim. Luckily it was the rear. I've gotten flats but not this catastrophic and not at this speed. Luckily it was a pretty safe situation.

Question: what might have caused this? Is there some usual cause for tires jumping off the rim? I wouldn't have thought this would be likely, given how tight fitting and difficult this tire/rim combination is to mount. I use a tire bead lever thing; when they get mounted I try and push the tire to the edge of the rim so the tube has adequate room to expand. One thing I am reluctant to mention is that I previously used soap to mount these rims. But that was several mounts ago and I think I wiped all the soap off the rim/tires. The other curious thing was that this was at least the second ride since mounting these tires (can't really remember), and the last two were 25, and 50 miles, enough to bounce them off the rim already, I would have thought.

Anyone do this often? Got any ideas?


back on the trainer..