I've been riding on the same rear inner-tube for several months without issue. I topped up the rear tube last week, went on ~10mi ride (including a rest in the middle), and had no problems.

I was about to ride again today, but when I looked at my rear wheel I noticed the tube was completely flat.

While removing and inspecting the tube I found two obvious bumps/bulges/protuberances/knobs on the inner-tube.

These bumps are near a spoke. They are on the inner wall of the tube.

I found the source of the leak. One of two bumps has a sizeable hole/cut. It's not a slow leak. If I try to pump it does not hold any air.

I remember now that last week, after that ride, I had heard an odd noise from my kitchen (where I store my bike) and couldn't find the source when I went to check on it. I thought, "that's odd", but didn't think twice.

In hindsight that noise must have been my rear inner tube very suddenly deflating. It wasn't a bang, but a sound vaguely similar to a bag of rice falling on its side and the grains coming out quickly then slowly then stopping. Sort of like a deflation now that I remember it!

The issue isn't glass or debris, and the tire does not have a bubble and otherwise is not deformed or damaged when I inspect it.

A similar question and answer makes me think that perhaps I overinflated it when I thought I was doing things like normal, but I've never experienced this particular behavior before and was curious. Also, that user did not notice these obvious deformities like I did, so I thought it could be a different scenario.

On feeling the rim tape, I do not notice the spoke protruding out at this spot, but I do notice an obvious dimple/depression in the rim tape at that spoke!

• What may have caused these bubbles?
• If poor rim tape may be at fault, must the rim tape be re-done?

Unfortunately I'd have to bring the bicycle to a shop mid COVID-19 lockdown for anything beyond changing the tube, as I'm only really equipped to swap out the tube with my skillset.

For context, the tire says 700x28c, the wheel says 700x18c/23c. That discrepancy between 28c and 23c always bothered me, but I have no idea if it matters. The bike has been like that since I bought it ~7 years ago and multiple mechanics at multiple shops have replaced my tubes and tires with similar ones and never mentioned it. The max PSI is 115 and I usually only inflate to ~100 PSI, if my pump can be trusted.