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TPU Tube experience and Failure mode

Old 06-13-24, 11:02 PM
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Originally Posted by terrymorse
TPU does stretch, just not very much. The material can elongate ~25% before permanent deformation, so a single size tube can handle 25-30mm without a problem.
Not in my experience. And 25% is pretty small compared to rubber which stretches more like 400%. To give some indication of how much 25% is, a 25mm tube expanded to 32mm is 28%. A 25mm tube expanded to 35mm is 40%. When I tried to put a 25 mm tube into my 37mm tires (48% increase), they formed the same kind of deformations as t2p picture shows. The “hernias” in mine burst, however.
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Old 06-13-24, 11:10 PM
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Originally Posted by t2p

no - like this

I was curious after viewing your picture - so I pulled two tpu tubes to inspect

Schwalbe Aerothan Endurance tubes *** installed in 40mm tires early 2022

not good

the good news is the seam appears to be strong and in good condition - the bad news is the material near the seam appears to be more susceptible to elongation / stretching / hernia / whatever (due to the nearby seam / joining method / whatever ?)

don’t know how much longer these would have gone before bursting - ? - the material is very thin at the location of the hernia’s

*** Schwalbe Endurance tube is intended for 28-35 mm tires

I will check two other bikes with Aerothan tubes - one bike has Endurance tubes with 32 mm tires - the other bike has Allround tubes with 40 mm tires
That’s not that dissimilar to what I saw nor dissimilar to what happened when I used undersized TPU previously. I can kind of blame myself for the cause of the first problem by using undersized tubes. However, the tube that failed last Saturday had been in use for several weeks and had be pressurized to the same pressure several times. The only difference was using a compressor to top off my tires instead of a floor pump.

And the hernias you are seeing could still fit into the model that I proposed in the post I linked to. The tube does fill out toward the tire first and then backfills into the rim channel. This could cause it to be stretched too much in the direction towards the rim causing the kind of deformation you are seeing.

Frankly, I wanted the TPU to work but at this point I am becoming less and less of a fan as I use them. They just have too many problems.
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Old 06-14-24, 05:16 AM
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Originally Posted by cyccommute
When I tried to put a 25 mm tube into my 37mm tires (48% increase), they formed the same kind of deformations as t2p picture shows. The “hernias” in mine burst, however.
Obviously user error. You of all people should have known better.
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Old 06-14-24, 07:33 AM
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Originally Posted by smd4
Obviously user error.
Well we all can’t be Mary Poppins, now can we?

You of all people should have known better.
Yes, I know a lot about plastics and materials but I don’t know everything about every plastic. I admitted I made a mistake and I’m trying to help people avoid the same expensive mistake. That said, I’ve seen no literature from the makers of TPU tubes that the tube should be carefully matched to the size of the tire. The size of the tube is so critical that the manufacturers should make tubes in several more sizes that more closely match the ERTRO sizes. Rubber doesn’t need to be that closely matched…although it needs to be closer to being a bit bigger than smaller…because it stretches.

The mistake I made with TPU tubes that were too small doesn’t explain the issue I had with a more properly sized tube nor the problem that t2p had with tubes that were also properly sized.
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Old 06-14-24, 08:24 AM
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Originally Posted by cyccommute
Not in my experience. And 25% is pretty small compared to rubber which stretches more like 400%. To give some indication of how much 25% is, a 25mm tube expanded to 32mm is 28%. A 25mm tube expanded to 35mm is 40%. When I tried to put a 25 mm tube into my 37mm tires (48% increase), they formed the same kind of deformations as t2p picture shows. The “hernias” in mine burst, however.
Originally Posted by smd4
Obviously user error. You of all people should have known better.
Ummm ... welll ... it seems to me science, as in "I have a hypothesis and want to rest it" followed by experimentation, is sort of ... how a lot of things are learned.

Mr. Cycco (pronounces well as "Sicko" or "Psycho" depending on your reactions to his posts ) did everyone a service by spending his own time and money testing the limits of TPU tubes. I am grateful because I don't want to spend the same money to do the same experiments.

I know if I choose TPU tubes I need at least 25 mm for my 28s, if that is all I can find at the time, and that I had best not try 23s in both my 23-mm and 28-mm tires because the tubes are too expensive to ruin in zero miles.
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Old 06-14-24, 08:31 AM
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Originally Posted by cyccommute

The mistake I made with TPU tubes that were too small doesn’t explain the issue I had with a more properly sized tube nor the problem that t2p had with tubes that were also properly sized.
actually - in my case the tubes were just slightly undersized - used a tube designed for 35 max in a 40mm tire (actual tire width 38mm)

but I have these same tubes on a different bike with smaller 32mm tires - and also have the larger ‘Allround’ tubes in the same 40mm tire (different bike) and will inspect them soon

Last edited by t2p; 06-14-24 at 08:36 AM.
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Old 06-14-24, 08:32 AM
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Originally Posted by Maelochs
Ummm ... welll ... it seems to me science, as in "I have a hypothesis and want to rest it" followed by experimentation, is sort of ... how a lot of things are learned.
I never needed to run an "experiment" to know to use the correct tubes in my tires.
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Old 06-14-24, 08:47 AM
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Originally Posted by t2p


no - like this

I was curious after viewing your picture - so I pulled two tpu tubes to inspect

Schwalbe Aerothan Endurance tubes *** installed in 40mm tires early 2022

not good

the good news is the seam appears to be strong and in good condition - the bad news is the material near the seam appears to be more susceptible to elongation / stretching / hernia / whatever (due to the nearby seam / joining method / whatever ?)

don’t know how much longer these would have gone before bursting - ? - the material is very thin at the location of the hernia’s

*** Schwalbe Endurance tube is intended for 28-35 mm tires

I will check two other bikes with Aerothan tubes - one bike has Endurance tubes with 32 mm tires - the other bike has Allround tubes with 40 mm tires
As with the RideNow tube, it looks like the discontinuity in the tube— in your case, the seam, on the RideNow the valve base— prevented the tube from stretching uniformily, creating a weak spot that extruded.

I’ve used quite a few of the Aerothan Endurance tubes in my 35mm tires on my gravel bike, and I’ve never seen them ribbed like that, and it’s feeding into this notion I’ve been cooking up where I wonder if there aren’t counterfeit Aerothan tubes out there.

I’ve purchased 4 off Amazon recently— two different orders— and I’ve seen some variations, inconsistencies, and just plain issues, one like the “pouching” near the seam similar to yours, which I’d not found in two other pairs of Aerothan which I bought direct from Schwalbe. I’ve got two other pairs installed on other bikes right now, and one of them has not inflated evenly, showing a pinch where that seam band is.

Something else that might be a clue in this, or a tool for understanding what’s going on, is what appears to be a lot number stamp on the tubes. I have 2 of the originals from Schwalbe, which I ran for something like 3 years, that are stamped 42/2020. Two of the later Amazon purchased tubes are stamped 44/2020 and 45/2020. Guessing the 2020 is year of production, I’m slightly surprised to be buying stock produced almost 3 or 4 years ago. I certainly could be looking at authentic tubes and just bearing witness to production inconsistencies from Schwalbe, too, but I just don’t know. I was going to order another pair from Schwalbe to compare and see, but I’ve already sunk a foolish amount of money into these tube and don’t want to throw good money after bad. However, the quality and performance of those first pairs was so sweet…. The second pair is still going, unpunctured/unrepaired, at the 4 year mark.

Maybe I’ll go pull that weird, pinched tube now and box up the lot and mail them Schwalbe for assessment and see if they might replace them for me.



The older, original ones are the darker ones in the middle. They were translucent white when new, but browned over the years.
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Old 06-14-24, 09:31 AM
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Originally Posted by chaadster
As with the RideNow tube, it looks like the discontinuity in the tube— in your case, the seam, on the RideNow the valve base— prevented the tube from stretching uniformily, creating a weak spot that extruded.

I’ve used quite a few of the Aerothan Endurance tubes in my 35mm tires on my gravel bike, and I’ve never seen them ribbed like that, and it’s feeding into this notion I’ve been cooking up where I wonder if there aren’t counterfeit Aerothan tubes out there.

I’ve purchased 4 off Amazon recently— two different orders— and I’ve seen some variations, inconsistencies, and just plain issues, one like the “pouching” near the seam similar to yours, which I’d not found in two other pairs of Aerothan which I bought direct from Schwalbe. I’ve got two other pairs installed on other bikes right now, and one of them has not inflated evenly, showing a pinch where that seam band is.
The herniation near the seam almost should be expected. Butyl tubes are joined by using a butt joint while the TPU seems to be an overlap joint. Since TPU isn’t stretchy, adding two layers of material makes it even less stretchy. On inflation the joint can’t expand down into the channel of the rim and the thinner material on either side expands to fill the void resulting in the deformation you and t2p see. The same is probably happening in my case but at the tire valve grommet. The tire valve grommet on a butyl tube is less stretchy than the rest of the tube but would stretch much greater than the hard plastic grommet used in the RideNow tubes.

I don’t think that t2p’s tubes are counterfeit. I think the ribs on the tube are probably do to the contact with the tire. You can see a crosshatch pattern on the tube that would match the internal crosshatch pattern of a tire.

The older, original ones are the darker ones in the middle. They were translucent white when new, but browned over the years.
The discoloration of the tube in your case raises some issues about aging. TPU is susceptible to UV degradation that has a negative effect on its physical properties. I found another study that says that it is susceptible to heat degradation as well. I suspect that it would become more brittle and even less stretchy with age.
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Old 06-14-24, 09:46 AM
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Originally Posted by smd4
I never needed to run an "experiment" to know to use the correct tubes in my tires.
I would agree with you concerning TPU tubes. The tire size range is printed right on the box and TPU doesn't stretch like the common rubber tube, so it should be a common sense thing.

With rubber tubes that doesn't apply. The back up tube for my tubeless 4.8" fat bike tires is a 26 x ~2.4 tube. That baby will stretch and work in a fat bike tire!!!

Last edited by prj71; 06-14-24 at 09:57 AM.
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Old 06-14-24, 11:52 AM
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Originally Posted by cyccommute
Not in my experience. And 25% is pretty small compared to rubber which stretches more like 400%. To give some indication of how much 25% is, a 25mm tube expanded to 32mm is 28%. A 25mm tube expanded to 35mm is 40%. When I tried to put a 25 mm tube into my 37mm tires (48% increase), they formed the same kind of deformations as t2p picture shows. The “hernias” in mine burst, however.
Yeah, putting a 25mm TPU tube in a 37mm tire is a "do not do, will likely fail" scenario. But a 30mm tire ought to work fine.

Tubolito's 700c tube is rated for 18-32mm tires. Same for RideNow. That's a surprising range of 78%, but I kind of doubt that 18 mm number is realistic. The "barely inflated" diameter of the RideNow tube is 20.5mm.
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Old 06-14-24, 06:21 PM
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Originally Posted by smd4
I never needed to run an "experiment" to know to use the correct tubes in my tires.
TPU ain’t rubber. When using TPU, there’s a learning curve that isn’t generally needed with rubber tubes because someone else did the learnin’ long ago for rubber tubes. The tube that herniated on me was the RideNow 36g race formula that is listed on the box as being suitable for 18mm to 32mm wide. I said that the tire I was using was a 37mm but I was mistaken. Upon checking, it is a 35mm wide tire which is just slightly outside of the size that RideNow says the 36g TPU is good for. It shouldn’t make that much difference but it did.

The tube in the picture above was the heavier 45g gravel tire that RideNow makes which is supposed to be good for from 32mm to 47mm. The wheels on the bike aren’t particularly wide but they aren’t particularly narrow either. The rims are Velocity Dyads with an 18mm internal width. Obviously this is too narrow for the tire valve grommet that RideNow uses but it is a fairly average rim width.

My point is that the heavier, wider, and better matched TPU tubes still failed. They don’t instill much confidence in me as to their robustness. I have a few more of the tubes running around on some bikes of mine but once they fail…which I have little doubt they will…I will be done with TPUs. Too delicate and too much trouble to bother with.
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Old 06-14-24, 06:29 PM
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Originally Posted by prj71
I would agree with you concerning TPU tubes. The tire size range is printed right on the box and TPU doesn't stretch like the common rubber tube, so it should be a common sense thing.
”Common sense” is based upon previous experience. TPU tubes are relatively new and no one should be expected to know that it doesn’t stretch without being told so. When the manufacturer gives a range of sizes that is close to the size of the tire that they are being used it, I would go with the manufacturer’s recommendations. They gave bad guidance.

The fact that I did use a tube that was well within the size range printed on the box and still had the kind of failure I saw with the narrower tubes as well as the type of failure that t2p documents says to me that there is something more systemic going on. In other words, there is a design flaw.

With rubber tubes that doesn't apply. The back up tube for my tubeless 4.8" fat bike tires is a 26 x ~2.4 tube. That baby will stretch and work in a fat bike tire!!!
Perhaps. Although I have noticed that the rubber on more recently made tubes isn’t as stretchy as tubes made several years ago. Tube size needs to be more carefully matched to the size of the tire than in the past.
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Old 06-16-24, 01:51 PM
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Originally Posted by squirtdad
  • TPU tubes are so light that is hard handle them and look for a leak and maintain position once you find a leak. Doing this in wind would be a zoo
  • I had do the dunk the tube in a filled sink to find the leaks.....I have not had had to do this with butyl tubes in forever, typically not practical in the wild depending on where you are
  • Punctures were hard to see even when found
I just did a 6 day bike tour in New Mexico, where I had my first experience with goatheads. I carried three spare tubes and a Rema patch kit. I had four flats on this tour. Two of them were such tiny holes from goatheads that I could not find them until I was back at my hotel room and able to dunk them in water. My fourth flat was a good old honest 1 1/2" nail that went straight into the tread and buried half length through the tube. By this time, I was carrying patched spare tubes and threw in the towel on finishing the last day's ride. Flats suck!

I jealously watched another rider who had tubeless tires. He had two flats, but fixed them with plugs, never having to remove his wheels and losing about 5 minutes to do each repair. The plugs held for the entire tour.

My rear wheel is a Rohloff hub and a bit more of a challlenge to remove in the field so I am considering tubeless for the next tour.
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Old 06-16-24, 04:12 PM
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TPU stretches just fine, and that stretchiness is why companies like Tubolito can not only make the claim that “While offeringweight saving up to 80 % compared to standard tubes, Tubos also offer double puncture resistance. Even the extra light S-Tubo models are still as robust as classic butyl tubes,” and they can further back that up with an unprecedented 1 year warranty against all punctures on their X-Tubo model, saying it can withstand 20mm of intrusion.

Similarly, Schwalbe claim their Aerothan TPU far and away “outstretches” butyl in plunger tests, both in terms of force it can withstand and depth of deformation before puncture:



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Old 06-17-24, 07:23 AM
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Originally Posted by chaadster
TPU stretches just fine, and that stretchiness is why companies like Tubolito can not only make the claim that “While offeringweight saving up to 80 % compared to standard tubes, Tubos also offer double puncture resistance. Even the extra light S-Tubo models are still as robust as classic butyl tubes,” and they can further back that up with an unprecedented 1 year warranty against all punctures on their X-Tubo model, saying it can withstand 20mm of intrusion.

Similarly, Schwalbe claim their Aerothan TPU far and away “outstretches” butyl in plunger tests, both in terms of force it can withstand and depth of deformation before puncture:



If TPU is so “stretchy” why does RideNow say this:
  • Instructions for Use: During the process of repairing the inner tube, inflate to 0.5 bar(8PSI) first, ensuring the inner tube is close to the tire's inner wall. Adjust the inner tube by pressing. Avoid heavy inflation without a casing to prevent irreversible damage; exceeding 0.5 bar(8PSI) will cause irreparable expansion
Schwable say this:

​​​​​​​

Can I inflate Aerothan Tubes outside of the casing?

The Aerothan Tube can be inflated carefully outside the casing until it is wrinkle-free and has a round contour (corresponds to max. 0.3 bar).
and Tubolito’s instructions say not to inflate past 8psi outside of the tire? The material can expand a bit but it does not rebound which is the opposite of what “stretch” means.
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Old 06-17-24, 08:05 AM
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Originally Posted by cyccommute
If TPU is so “stretchy” why does RideNow say this:

Schwable say this:

and Tubolito’s instructions say not to inflate past 8psi outside of the tire? The material can expand a bit but it does not rebound which is the opposite of what “stretch” means.
If overinflating tubes is your fetish, you should start a YouTube channel for it. I mean, it’s already been done, but probably no one is providing as many uninformed takeaways as you can.


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Old 06-17-24, 10:25 AM
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update update update update update

so I removed the tpu tubes that showed signs of future failure - replaced them with a lightweight butyl tube specifically designed for the tire size

wanted to be safe

planned to do a ride in an area where there is not much other than a river below on one side and a mountain on the other side - did not want to deal with a flat - especially if we would be returning late in the day / early evening

and I flatted

rear tire - the tube developed two small areas where it stretched excessively and developed two ‘hernias’ - and one let go

I never flat !

the tubes - Schwalbe SV18 ‘extralight’ - made for 700c 28-42 mm (or 28-45 mm depending on your interpretation)

the tires - Conti Terra Speed 700c x 40 (actual width around 38 mm)

air pressure - I typically run 55-60 psi on this tire - but did initially pump up to almost 70 when first installed to enable the tire bead to sit correctly / uniformly

the tubes did appear to be fairly small - especially for a tube rated up to 42 mm - ? - but I thought they would be ok since they were butyl

the rear tube failed around 23 miles into the ride - with 14 miles remaining

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Old 06-17-24, 04:04 PM
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Originally Posted by chaadster
If overinflating tubes is your fetish, you should start a YouTube channel for it. I mean, it’s already been done, but probably no one is providing as many uninformed takeaways as you can.
You do realize that tubes have to have some air in them to find flats to repair, don’t you? I dare you to pump up a TPU tube to the size of the one in the video and then get it back to the size it was originally. Making rubber tubes oversized helps in finding flats. As discussed in the thread above, that can’t be done with TPU which makes flat detection much harder. Been there, done that. Even the one in the picture I showed was difficult to detect because the tube couldn’t be pumped up to a larger size. In a dip tank, it was a very slow leak.
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Old 06-17-24, 06:11 PM
  #120  
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Originally Posted by cyccommute
Even the one in the picture I showed was difficult to detect because the tube couldn’t be pumped up to a larger size. In a dip tank, it was a very slow leak.
Yeah, but ....


No , seriously, I just had a leak like that ... in a butyl tube. Probably the hardest leak to find in my entire cycling experience. And that was with the tube inflated to well over twice its normal (in-tire) size.

I cannot imagine that i will gain enough from TPU tubes t make u for the pain of looking for invisible leaks. Also, if I ruined a couple TPUs while looking for leaks .... yeah, I am to old for that kind of frustration.
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Old 06-17-24, 11:57 PM
  #121  
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You guys like your big, instantly flat, punctures, eh? Coooool.
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Old 06-18-24, 12:26 AM
  #122  
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Originally Posted by chaadster
You guys like your big, instantly flat, punctures, eh? Coooool.
No, sir .... but for smaller punctures and slow leaks, immersing a tire in water is the best way I know to find those leaks. If I cannot inflate a tire enough to create a visible bubble stream, I cannot patch that tire and must throw away that tube.

You like throwing away tubes because you can't find the hole?

Of course not, and of course youi never said that.

Well, no one said they liked big punctures either.

What I said was that even having the ability to inflate 28-,, butyl rube to two and a half times is normal size, I found it hard to locate a puncture, which means ... if it had been TPU where I could only inflate it to a few psi ... I might not have been able to find that puncture.

So, straw men aside ... what is your success rate with TPU tubes? And if you are so pro-TPU ... perhaps you would like to buy me some to test. if they are as good as you say, I will keep using them.

Otherwise, as I said, I don't see where TPU is ready for My world, however well it might do in your world. Not telling you what to do, not even that interested in what you do except as it relates to what I do and what I might do ... and so far, based on what you and others have posted, I made the choice I explained above. Thanks for helping.

Everything clear now?
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Old 06-18-24, 06:58 AM
  #123  
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Originally Posted by Maelochs
No, sir .... but for smaller punctures and slow leaks, immersing a tire in water is the best way I know to find those leaks. If I cannot inflate a tire enough to create a visible bubble stream, I cannot patch that tire and must throw away that tube.

You like throwing away tubes because you can't find the hole?

Of course not, and of course youi never said that.

Well, no one said they liked big punctures either.

What I said was that even having the ability to inflate 28-,, butyl rube to two and a half times is normal size, I found it hard to locate a puncture, which means ... if it had been TPU where I could only inflate it to a few psi ... I might not have been able to find that puncture.

So, straw men aside ... what is your success rate with TPU tubes? And if you are so pro-TPU ... perhaps you would like to buy me some to test. if they are as good as you say, I will keep using them.

Otherwise, as I said, I don't see where TPU is ready for My world, however well it might do in your world. Not telling you what to do, not even that interested in what you do except as it relates to what I do and what I might do ... and so far, based on what you and others have posted, I made the choice I explained above. Thanks for helping.

Everything clear now?
Complaining about potential difficulty finding holes in tubes is the most petty, trifling, missing-the-forest-for-trees kind of thing I’ve ever seen.

Really…if finding leaks is such a big part of your innertube satisfaction assessment that hypothetical, undiscoverable pinholes is the the stopper, the point on which you decide a tube is not for you, you’ve lost the proverbial plotline.

TPU tubes can be readily had via Amazon less than price of butyl at a bike shop, so that you think you’re being clever asking me to buy you some tells me all I need to know to understand that you’re more serious about imagining problems than discovering the truth.

Maybe you should team up with Mr. Overinflation as his loyal sidekick, The Pinhole Kid. You guys could have a YouTube where you let your imaginations run wild and focus on all the wrong stuff for product reviews. That would at least be novel.
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Old 06-18-24, 07:11 AM
  #124  
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whew...too exhausted, after reading the post and responses, to add my well thought out and science based techno babble...er umm meant useful advice and anecdotes...to the party
pumping up my Topolito tpu tubes and going for a ride...fingers crossed I don't get a flat...
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Old 06-18-24, 07:51 AM
  #125  
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Originally Posted by chaadster
You guys like your big, instantly flat, punctures, eh? Coooool.
I’ve had plenty of slow leaks with butyl tubes and plenty of instant flats with the TPU tubes. Again, in a relatively limited usage…about a year now…I experienced 4 flats in 2 days due to something in the tire that had not punctured the butyl tubes and due to the bad patches. I’ve had one “normal” flat which I don’t blame on the TPU nor fault the tubes for, although the repair was much more difficult than a butyl tube repair. I’ve also experienced two tube killing malfunctions of the tube as in my picture above and similar to those experienced by t2p. Both were due to the inability of the TPU material to stretch, no matter what you and Schwalbe say.

As a tube material, I find these tubes to be lacking. They are too difficult to patch reliably. They aren’t nearly as flat resistant as the manufacturers would have you believe. They are unreliable in terms of inflation and damage due to inflation. And they are far too expensive for all the trouble. Yes, they are light but that, in my opinion, doesn’t make up for all their problems.

Originally Posted by chaadster
Complaining about potential difficulty finding holes in tubes is the most petty, trifling, missing-the-forest-for-trees kind of thing I’ve ever seen.

Maybe you should team up with Mr. Overinflation as his loyal sidekick, The Pinhole Kid. You guys could have a YouTube where you let your imaginations run wild and focus on all the wrong stuff for product reviews. That would at least be novel.
Speaking as “Mr. Overinflation”, it is rich that you are telling someone else that they are “missing the forest for the trees”. My point about overinflation of the TPU tubes was not meant to be a comment on being unable to inflate the tube to find leaks. It was meant to illustrate that the manufacturers warning about overinflating the tubes outside of the tire because the tube will be damaged by doing so. That goes to illustrate the TPU tube’s inability to stretch or, alternatively, that the tube will deform rather than spring back to the original shape like rubber will.

You completely missed the point!
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Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
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Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!




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