8

I have a puncture in my tube on a bump in the tube that coincides with a dip in the spoke hole, and am not sure if I need to replace the rim tape or not.

I have seen numerous posts about spoke induced punctures recommending either new rim tape if broken or filing the spoke down. However, over the spoke hole where my puncture occurred, the rim tape (which appears to be cloth tape, I did not install) seems fine, although a little off center but still covers the holes. There is nothing sharp, no holes in the tape, or any visible damage to the tape.

Is the puncture simply unlucky, or is there an issue with the tape, even though I cannot see any problems? I am not sure if the dips in the rim tape, which cause bumps in the tube, is an issue. From what I've seen, this is a common occurrence.

Of note, the bicycle has not been used for a couple months over the winter.

Image of spoke hole where tube was punctured

Tube with puncture

Improve this question
5
  • What kind of puncture is it? Pinprick, cut, jagged? And are you sure it's on the inside of the tube? I notice the rim join is in the photo - is it smooth?
    – andy256
    Commented Mar 15, 2015 at 20:27
  • I am positive it is on the inside; it is on a bump that coincides with the dip in the rim tape over the spoke hole. You can barely see the puncture in the photo, and it is slightly bigger than a pinprick but not really a cut or jagged
    – Sean
    Commented Mar 15, 2015 at 20:39
  • As for the rim joint, it is almost perfectly smooth, with a slgiht edge you can feel with your fingernail. But this is not where the puncture is, as I am positive the puncture is over the dip in rim tape over the spoke.
    – Sean
    Commented Mar 15, 2015 at 20:43
  • 1
    Check for loose spokes.
    – Daniel R Hicks
    Commented Mar 16, 2015 at 2:57
  • 1
    see also bicycles.stackexchange.com/questions/67606/…
    – Swifty
    Commented May 10, 2020 at 15:22

6 Answers 6

Reset to default
8

I would recommend replacing rim tape with a modern plastic one. You could inspect the existing cloth one, but then you would need to remove it to inspect the spoke ends. Cloth tapes often don't survive removal.

When the tape is off, inspect the spoke ends and the nipples. If one is sharp, use emery paper to remove the burr. Do not use a file: a single filing always avoids removal and causes another puncture.

Repair the tube and do whatever you think will bring luck - punctures like this can be tricky to solve.

It's possible that the cause was grit that happened to work it's way in under the tube, and subsequently fell out, but the hole looks like a spoke puncture to me.

Improve this answer
2
  • 1
    And, I should add, of course you should inspect the inside of the tire, even though it does not seem to be implicated :-)
    – andy256
    Commented Mar 15, 2015 at 22:25
  • If you're using a tube, when are you going to want to remove the rim tape before it is damaged/worn through anyway? Good quality cloth rim tape (e.g. from Velox) is inexpensive, and can last decades).
    – Batman
    Commented Jul 20, 2017 at 19:55
5

It appears to be over-stretching of the material the inner-tube is made from. Excessive stretching causes the material to thin out and fail.

I've experienced this type of puncture on my mountain bike (Mongoose Blackcomb). My tires are at least twice as wide as the rims and I imagine a cross-section of the tire-tube-rim assembly would look a lot like an antique keyhole or a "keyhole" mounting slot in the back of a wall-mounted item meant to be secured to the wall with screws.

It seems that the inner tube stretched (in my case) down into the rim and eventually punctured spontaneously.

I put talc (baby powder) inside the tire in an attempt to lubricate the inner tube and allow it to stretch more evenly around its cross-section and I doubled-up on the rim liner. So far my flats are greatly reduced.

Improve this answer
3

Low tube pressure and similar dips, I have had it, and it caused cut, sometimes double cut, when hitting a curb or other crush on the pneumatic. Those made the air in the tube go out really fast. I changed rim tape and now keep pressure high, i e pump the wheel more often.

Improve this answer
2

A bit late getting onto this, but I am looking at exactly the same problem. It is like under high pressure (110psi in my case) the inner tube is pressed out through the spoke hole and I guess becomes so thin it bursts.

It cannot be a spoke puncture as the tape is still ok with no signs of being punctured.

I have ordered high pressure 120psi rim tapes and will re-try.

Improve this answer
2

Replacing the tape, as per @andy256, should do the trick. But if acquiring new tape were not an option, you could add one or more extra layers on top of the old rim tape, in order to soften the concavities in each spoke hole visible in your picture. There are several alternatives here. This one seems particularly appealing.

Improve this answer
2

If you're getting this a lot, and changing the rim tape doesn't help then it could be the holes are too large for the pressure in your tubes AND the width of your rim tape (which is regulated by the width of the valley)

Closing up the rim holes should resolve the cause, at the cost of some additional rolling weight. There exist retail products to do this, called "spoke plugs" or "VeloPlugs" and you need one per spoke.

These only work with double-walled rims where the nipple is below the tube. For old single-wall rims these won't help.

enter image description here

Improve this answer

Not the answer you're looking for? Browse other questions tagged or ask your own question.