Been raining since Sat morning. Still raining here at Bukit Batok. Could not join Taiwoon and friends for the City Ride on Sunday morning because the rain was just too heavy. Apparently the weather at Lavender was pretty good, not raining at least.
Discovered that my rear tire was punctured on Sat night. Quite strange because I cycled a bit on Sat morning, and there was no problem. In the afternoon I checked the tires and found that they were alright. However at night just before I went to sleep, I checked the tires and found that the rear tire was flat!
Had to remove the rear wheel to find the cause of the puncture. Struggled quite a bit to get the tire off the rim, because its quite tight. Found that the puncture was on the inside of the tube, on the side resting on the rim tape.
Small cut, as can be seen from the picture above. Usually this will be due to the spokes poking through the rim tape, but then I checked the tape and it was perfectly fine. Also checked the inside of the Kojak tires as a precaution, nothing found. Luckily I had a spare tube, left over from the Pengerang ride. Before putting the new tube on, I also taped the inside of the rim with duct tape, for extra protection on top of the rim tape.
Put the tires back on the rims and the wheel back in the bike. Went to sleep, woke up at 5+am in the morning to check the weather. Still raining heavily. Had planned to cycle down to Lavender from Bukit Batok to join the ride, but the weather was just lousy over here. Went back to sleep instead.
Then today, on Sunday morning, I decided to take out my front wheel and put extra duct tape on the inside of the rim also, to prevent the same problem from happening. Again, checked the tires and rim tape, no problem. Duct taped the front rim and put back the tube and tire.
I was in my room in the afternoon, when suddenly I heard a pop followed by hissing. Didn't know what it was, so went out to check. Realised that the front wheel had gone flat! What is going on?
Removed the front tire and tube. Saw a long cut on the inside of the tube, somewhat similar to that of the rear tube but much larger.
This is really mysterious la, because the bike was just sitting there and it can puncture by itself. Once again, checked the tire and rim tape. Nothing detected. Also checked the inside of the rims for anything sharp, nothing found.
Decided to take out both my front and rear rims, tires and tubes, and make a trip down to MBS to see if anyone can help me solve this problem. Right now the rear wheel is holding up fine with the new tube, but I have let air out of the tube just in case.
Some possible reasons for the mysterious self-punctures:
1) Batch defect with tubes? Tubes are at least a few months old, tires even longer. Rims are less than 2 months old. Been through quite a bit of cycling on these wheels, no problem so far.
2) Wire bead of Kojak tire. The rubber on some parts of the bead has peeled off, leaving the bare wire exposed. But the wire is not sharp, and the cut was on the inside of the tube anyway, and not the side where the wire bead is.
3) Cold weather?
4) Tire levers may have damaged the tube when I tried to remove the tire. Unlikely as I have changed many tubes and tires before without problem, but still a possibility.
Summarizing the story, both my front and rear tubes have been punctured while the bike was just sitting there. Both were caused by cuts on the inside of the tube, on the side of the rim tape. Reasons for puncture might not be the same though. Hopefully the people at MBS can help me solve the mystery.