Here's a photo:
This is confusing me because of several things:
- This is clearly on the inside of the tube, so it's not something I rode over
- This happened while the bicycle was standing untouched on my balcony
- You can see two bumps in the rubber, of which one has ruptured
- There are no other bumps like this on the tube
- The tips of the spokes are all covered with a rubber tape which seems to be unpunctured
- No tips of spokes stand out more than others (or any other irregularities), including the ones that would correspond with this puncture
- However the location does match one of the spokes, so it seems likely there might be a relation
- This has happened before, but doesn't happen all the time (maybe once or twice per year).
Any ideas what's going on here? Do I need to replace the rims? They are pretty old anyway...
Update, a little later:
So, I changed the tube one evening, and the next day was a bit hotter again and - poof! The next one failed too. In the exact same fashion, in the exact same place. I didn't even get the chance to ride it!
So this time I thought of taking the advice from here to heart and a few days after that went out and got two things - more new tubes (this time from a different brand, although I think it's a cheaper one) and a patch kit.
Then, later yet, I tried to patch it. It seemed to work, so I reassembled the tire and pumped it up to my regular 3.5bar (around 50psi).
It looked good, for about 10 seconds. Then with a loud hiss the patch failed.
You can see a bulge in the middle of the patch and where it came open on the side.
Now, I suspect this might just be me not knowing how to patch right. I've never done this before. I did try to follow the provided instructions, but maybe I didn't sand the place down well enough, or didn't apply the glue thoroughly enough, or didn't let it cure long enough. Who knows.
Anyways, I went back to what I know and put in a new tube. This one seems to be holding - so far. Haven't had any hot days though.
Before putting it all back together though I did one more thing - I took a picture of the rim at the place where the break was. And... best I could tell, it was BETWEEN two spokes, not on top of one.
Here's the suspect area, with and without rim tape:
And... I still don't see anything special there. The tape and the spoke tips are the same as everywhere else.
I did however notice something else - the bumps on the broken tube are on both sides of what seems to be some sort of a rib. Could that have something to do with it? Do tubes have a maximum pressure rating? I didn't see any, and the tires say "2.7 to 4.4 bar", so I think I'm within bounds, but...