Mystery Punctures Diagnosis

[buschwacker]

Hello all, I come seeking your expertise regarding the puncture in my rear inner tube pictured below. This is the second time I’ve gotten a puncture like this and I’m at a loss regarding preventing them. This puncture occurred last night after inflating to 70 psi, the maximum limit on the tire.

For background, I ride an ebike as a general purpose errand runner, with Schwalbe Marathon Plus tires and a puncture strip between the tube and tire. I’ve inspected the tire and found no punctures and likewise have inspected the rim tape and found no exposed spokes. Moreover, I took my bike in to my LBS for a puncture like this just last month and as part of their tune-up they put in a new tube.

Any input on the cause is most welcome – I used to ride this bike in the same configuration 17 miles daily to and from DC for my commute and never once experienced a flat like this. Now with the pandemic, I ride it hardly at all by comparison and have gotten two flats in a short amount of time. My best guess is the puncture strip may be pinching or abrading the tube. Has anyone experienced something like this before?

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[DrP]

@buschwacker 206124 wrote:

Hello all, I come seeking your expertise regarding the puncture in my rear inner tube pictured below. This is the second time I’ve gotten a puncture like this and I’m at a loss regarding preventing them. This puncture occurred last night after inflating to 70 psi, the maximum limit on the tire.

For background, I ride an ebike as a general purpose errand runner, with Schwalbe Marathon Plus tires and a puncture strip between the tube and tire. I’ve inspected the tire and found no punctures and likewise have inspected the rim tape and found no exposed spokes. Moreover, I took my bike in to my LBS for a puncture like this just last month and as part of their tune-up they put in a new tube.

Any input on the cause is most welcome – I used to ride this bike in the same configuration 17 miles daily to and from DC for my commute and never once experienced a flat like this. Now with the pandemic, I ride it hardly at all by comparison and have gotten two flats in a short amount of time. My best guess is the puncture strip may be pinching or abrading the tube. Has anyone experienced something like this before?

When you say “Puncture strip” do you mean something like rhinodillo strips? If so, then that is likely the problem. I had three flats in 2 days due to that. The strip was cracking longitudinally and when I went over bumps, the crack would open, the tube would go in and either another bump or just pressure would push air in and it would pop. When just feeling the strip, it isn’t obvious, so I didn’t realize that was the cause. I took it out and started inspecting in closely and found the cracks. I stopped using them entirely and got better tires.

[buschwacker]

@DrP 206161 wrote:

When you say “Puncture strip” do you mean something like rhinodillo strips? If so, then that is likely the problem. I had three flats in 2 days due to that. The strip was cracking longitudinally and when I went over bumps, the crack would open, the tube would go in and either another bump or just pressure would push air in and it would pop. When just feeling the strip, it isn’t obvious, so I didn’t realize that was the cause. I took it out and started inspecting in closely and found the cracks. I stopped using them entirely and got better tires.

Yes, that’s the sort of thing I am using. I’ve got one in the back but not in the front, and I haven’t had any flats in the front. The strip has been in there for about two years now, so perhaps it’s deteriorating and causing the issue.

[buschwacker]

By way of update: I took the bike into LBS (Handybikes DC is great as always) where we scratched our heads over it. The techs noticed that the tube had a pattern of wear that was consistent with friction or rubbing, and that wear pattern was the same width as the anti-puncture strip. So the best theory is that the strip was moving around in there due to the weight and speed of the ebike. The strip is now gone with a new tube in place – I think the strip was the culprit. The irony of an anti-puncture strip causing a puncture was lost on no one.

I also remember now that when I put the strip in two years ago, the supervising tech had me puff talcum powder on the tube to help get it in the tire. When that original tube got a puncture from a nasty nail, the new one went in with no talcum powder. Perhaps that talcum powder was providing enough lubrication to prevent friction between the tube and the anti-puncture strip for the two years it was in there? We may never know.

[Author]

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