29-er puncture problem #2

Events of the past few days have established that my punctures are not being caused by protruding spoke ends, even thought all recent punctures have occured on the inside part of the tube where it is next to the rim tape.

I recently installed some good cloth rim tape, yet, on pumping it up, it developed an immediate puncture without me even riding it.

The puncture was again on the inside part of the tube and directly over a spoke nipple.

In desperation I decided to beef up the rim tape even more by making a second layer of rolled newspaper; the idea being to take it for a ride to confirm or deny the theory that spokes were causing the puncture.

I installed tube and tyre, then left them, planning to go for a ride a few hours later.

A few hours later I found the tube had developed another puncture, again on the inside next to the seam.

I repaired the puncture, pumped up the tyre, and, seconds later, it punctured and deflated (again on the inner part, again near the seam, but this time between two spoke nipples, not over one).

At this point I decide that the tube must surely be defective, put it in the bin, removed the newspaper rim layer; then installed a different (though not new) inner tube.

I pumped it up to 55 psi with the track pump and put it to one side.

Seconds later it deflated!

This time the damage with a three inch slit in the tube, running along the seam.

I conclude from this that spokes are not the cause (as all these punctures have happened without the wheel being ridden, and at tleast two while there was both cloth rim tape and thick paper between the tube and the spokes).

So I’ve tried to do some lateral thinking about what things I’ve been doing different during this period of very excessive punctures.

Then it occured to me- I bought a track pump.

I did this because of several consecutive punctures which I believed were ‘pinch flats’ (so I thought my tyre pressure was too low and bought a track pump).

I now believe that these were not pinch flats at all, as the distictive short line of holes matched a defect I found in the tyre.

All the punctures that happened after that (since I repaired the tyre defect) have been of a totally different kind i.e. on or near the inners seam.

So I’m thinking, could it be that excessive pressure is blowing the tubes?

Though the tyre is rated 40-65 psi, maybe, for whatever reason, my combination of tube and rim just can’t take it.

Equally possible, maybe the pressure guage of my new track pump is defective, and I’m actually going way above the 50-55 psi I’ve been trying to achieve.

What I need to do next is repair the tube and pump it up to the pressures I used to use (i.e. use the hand pump) and see if the punctures stop.

Also maybe buy a pressure guage to see if it agrees with the track pumps readings.

But I’m just wondering if-

  1. the above reasoning seems plausible

  2. for those of you with lots of inner tube experience, in situations where a tube is wrecked by being overpumped whilst in a tyre, does the hole tend to occur on, or near, the seam?

To me if the tire was overpumped it seems like the seam would be the most likely spot for a hole to occur on since the seam would (I think) be the weakest spot of the tire and the first part to blow out under high pressures.

Never happened to me but it seems plausable.

Well the spokes could be too long, and just inflating the tire presses the rim tape enough that the spoke end pokes through. It would be worth checking to see that each of the spokes does not protrude through the nipple end.

Another suggestion: try a different tire. Perhaps the inner surface of the tire is cutting the tube somehow.

Another: buy a different brand tube from a different shop. Perhaps the brand you have had a faulty run.

Another: like you said, work with air pressure, and purchase a separate handheld gauge.

You may be having multiple problems at once.

i bet your not using a real 700x52cm 29er tube, are you?

if not a regular tube will fit but becomes paper thin by the time it expands far enough to fill that big of a tyre.

Wow, this is serious.

Is it possible that you are somehow pinching or damaging the tube on installation? Do you put enough air into the tube to give it some shape, mount it in the tire and give the whole thing a shake to align the tube properly BEFORE you get near the rim? Is it possible that a tire iron or other tool pinches the tube while you are prying the bead onto the rim?

It’s also possible that your tire has something inside that is cutting the tube. Have you flexed and felt all of the surfaces inside the tire for protrusions? I had a tire that did this once. There was a tiny piece of glass not much bigger than a sand grain lodged in the tire that only appeared when I flexed the tire. It had been driven almost all the way in to the tube by riding.

I’ve checked the spoke ends out, they’re fine.

I’m not concerned about sharp bits in the tyre as these punctures are occuring exclusively on the inner part of the tube (next to the rim).

After 3 weeks of constant puncture repairs I am now totally paranoid about

installing the tube correctly :slight_smile: I inflate it lightly before putting the tyre fully

on, then squeeze all round the tyre beads to ensure the tube isn’t caught between

bead and rim, then inflate it more, then repeat the squeeze etc.

Tyre irons are definitly not a problem as I don’t use them; whilst searching the

web for solutions to this puncture thing I happened upon a nice method of removing

and installing tyres that makes irons unnecessary.

Jagur- you’re right, I’m using, ideally 700c x 35-45, as that is the best I can get

from my LBS, and now they’ve actually run out of those and are telling me that 700c

x 40 are OK for 29-ers.

The only 700 x 52 I’ve seen are on unicycle.uk.com and they come only with Presta

valves, which I don’t like.

If I do upgrade the rim I will be making it a priority to track dowm some proper 52


However, prior to 3 weeks ago, 700 x 45 tubes worked OK, and now they don’t; this

thing has gone from being an annoying inconvenience to a full blown mystery.

Last night I attempted to inflate the repaired tube with a hand pump only, it blew

well before the tyre got hard.

The puncture occured under a previous repair- I can only assume that the repair

wasn’t good, or that the tube is finished; I put it in the bin.

That left me with only one 700c tube, and it’s only a 700 x 40.

I’ve nothing to lose by trying it so it’s installed and I’ll ride it later.

Obviously, a 700 x 40 is not ideal, but, if it survives a few rides it’ll mean that

the previous tube was almost certainly defective or damaged.

I bought the 29’’ tube that unicycle.uk.com supply and have had it in the Notos XC on my nimbus 29er for a few months now and have done loads of Cross Country/Muni on it and have had only one puncture caused by a thorn, I pump it up to about 45 psi. Up untill then I had never used a presta valve but didn’t find it a problem as I used the adaptor that came with my foot pump, just wondering why you don’t like presta valves, it just might be worth trying it to see how it goes.


Mainly because my track pump presta valve adapter doesn’t work- I can pump up a presta valve but it leaks loads as I’m doing it.

Why do you pump up your Notos to 45 psi? Is that what it says on the tyre or do you just find it a better ride?

Like I said above I’m currently wondering if my pumping the tyre to 50-60 psi is a factor in my recent spate of punctures, as they seemed to start around the time I bought a track pump (previously Iused a hand pump which presumably wouldn’t get it up to those kind of pressures).

Because I mainly ride it off road and it feels about right, it seems to soak up the bumps with out being too bumpy and it’s still within the recomended pressure range, I think the tube that I got off unicycle.uk is quite good as once I didn’t seat the tyre properly and the tube escaped (while it was static and I wasn’t watching) and it had bulged out to about what must have been 8 inches in diameter all the way around, probably larger in places without causing any damage although I don’t know if any lesser quality tubes would inflate to this size without bursting, but I’ve never seen a tube go that big before.

Close your eyes and run your hands along the inside of the tire and the rim. Feel for anything sharp. I had a similar problem, I thought it was caused by faulty valves, but I was getting pinhole leaks from thorns. A patch kit solved the problem.
My Coker had a burred rim sandpaper solved this problem.


Had a couple of rides with the new tube and lower (hand pump pressure)- a quick half hour last night and another this afternoon.

No punctures, which is an improvement :slight_smile: but too early to come to definite conclusions.