terrymorse 

The burden of proof falls upon the person making the claim.

downtube42

Imagine if you will that someone invented a new coffee cup that instead of having the well known handle has instead a series of small bumps and wispy thin hoops that fit the hand exquisitely. It does take practice to relearn how to pick up a coffee cup, and they must be hand washed and stored in parrifun to prevent breakage. Nonetheless, a segment of the population adapts, and proceeds to ridicule those who lack the will to change, or worse the intellect to realize their need to change.

A more reasonable perspective is people don't all value the same things equally.

I value roadside repairability very high, and I value a few watts rolling resistance very little. Reduced pack size is a plus, but it doesn't sound like a net positive. Needing to relearn how to do something I can currently do roadside in the cold dark rain at 1am is not a positive, particularly when I might need to do it in exactly those conditions.

smd4

My claim was that glass is more elastic than rubber. And I left a link.

Man, it’s like you’ve never blown up a balloon.

terrymorse 

Which I agreed with, but I also commented that it's irrelevant.

My question was how does rubber relax in response to deformation, and by how much? Here's the result from one static test(*):

Stress Relaxation after 7000 seconds
50% strain : 28%
20% strain : 28%

So rubber softening from stress relaxation is a real effect, and it seems to happen quickly, then level out.

* - Sharma et al, Parameter estimation of butyl rubber aided with dynamic mechanical analysis for numerical modeling of an air-inflated torus and experimental validation using 3D-laser Doppler vibrometer, 2019

Maelochs

Man, a guy learns one interesting but pointless fact and tries to act like a scientist, and everyone calls him out because he doesn't really understand what he is talking about in relation to what the conversation is about.

How unfair ..... I think.

daviddavieboy

This point may have me sold alone. I am in the habit of airing my tires every day but when I commute and come home in the evening the air loss is noticable.

cyccommute 

In the colloquial meaning of "elastic"...and the polymer meaning of elastic...rubber returns closer to its original shape after having been stretched further that other materials. Rubber will stretch to a factor of 10, roughly, over its original length and return to original shape...at least close enough for most applications. Any deformation from stretching is hardly measurable. Glass, on the other hand, can't be stretched at all under the same conditions. For the purposes of this discussion, rubber stretches and returns to its original shape while TPU doesn't.

rsbob 

And down the rabbit hole we go once again.

jadmt

fixed it for you....

prj71

OP: Get some Park Tool Super Patches and put it on your TPU tube. It will work just fine.

https://www.amazon.com/Park-Tool-GP-.../dp/B000WY730O

Garthr

Along the lines of these tybes being plastic, has anyone tried to fix a TPU puncture with regular Gorilla tape ?

santa fe 2926 

My experience with TPU has been very unsuccessful. My local group got into the tubes, with the thought less punctures, and greatly reduced weight over butyl’s. So I first rode some inexpensive green ones from Amazon. They went 25 miles and poof, on the joining seams in the tubes. Sent them back. Then some aerothons from bikeinn, along with a patch kit. Again 25+ miles and one flatted. Used the water check system, drew a circle around the leak, flipped the tube over and laying it flat on the marked hole, drew a larger patch size circle. Flipped over, cleaned with alcohol rub and applied patch. The patches seem to work, but on first ride flatted again at 4 miles. Then I got some Nano’s from Australia, and some tubes and sealant from E Dubie. With the sealant the Nano’s first flat got me home with two pump ups, the second flat was instantaneous. Have not tried the e Dubie tubes, which I think make the Rene Herse tubes. Same tires, bikes routes as butyl, so I can’t explain my bad luck. I’ll eventually try the E Dubie, but no sealant.

SoSmellyAir

I switched to Pirelli Smartube TPU tubes (yellow, 700x23-32c) in new GP5K clinchers a few months ago and had my first flat this past weekend. On Saturday, I rode over something, heard a pop from the rear tire, and lost pressure rapidly but was able to come to a safe stop. Got home, the tire had an L-shaped gash pretty near the bead, 3 mm long per arm of the L, so I reluctantly tossed it. The TPU tube had a double pin hole snake bite. Patched it with a Pirelli Smartube patch kit, which comes with (1) a few 70% isopropyl alcohol wipes, (2) two sizes of patches in the same TPU material as the tube, and (3) Rema Tip Top Camplast cement. Followed the included pictorial instructions to patch the tube, except I also clamped the patch to the tube for about 20 minutes. The tube held on my Sunday ride (including a 36 mph descent) and is currently still holding air at about the same pressure as the front tube.

rsbob 

Maybe you are paying too much. Have 600 miles on these with zero issues.

prj71

I'm chalking up some of these flats to user error. I have the Pirelli and Schwalbe TPU that I've tried and so far zero issues setting them and zero issue in hundreds of miles of use.

santa fe 2926 

Not user error, ninth flat on TPU’s in 300+ miles. Yesterday the mowers were out on river trail, mowing as low as possible (if they mowed at 5 inches, the grass would choke out the sticker plants), and thru out some of last years stickers, and I got one. The rear butyl made it thru ok.

chaadster

I'd chalk some of them up to cheap TPU, too. All TPU is not the same, we know that, so it logically follows that they all do not perform to the same standards. Some, like Schwalbe Aerothan, exalt its puncture resistance, and Tubolito X-Tubo offer a 1 year guarantee against all flats. On the other hand, some make no claims about their TPU tubes' durability at all.

Maelochs

user error: you made the error of using our product.

Bafanguy

My first ever set of tpu's, they were perfect for the first week. Then suddenly I had a flat, and discovered that the tube had a hole on the INSIDE edge of the tube, facing the rim. Inspected the rim, couldnt see anything that would puncture the tube. Put a new tpu tube on, and have been issue-free after a month of daily riding. So weird.

cyccommute 

Kind of like this?




I had this happen once before but it was because the tube I was using was far too small…TPU does not expand!…but this tube had been in use for several weeks and even been previously pumped up to the pressure I was using in this one. The only real difference was that I used the compressor at the co-op to top up this tire. The tire wasn’t flat or even that low but it developed this hernia in the 5 hours I was at the shop.

chaadster

I had the same failure mode on a couple of those cheap RideNow tubes, too, the rather light 24g ones (I think they go as light as 19g in the same size!). Your conclusion, though, that TPU doesn't expand is not correct, though. That failure is a construction or manufacturing error almost certainly, I'm guessing because the valve base, the round part, isn't deforming properly when inflated, causing the extreme stretching in the tube at the edges of the base. It could also be, based on my case where I'd installed them in old, 13mm internal rims, that the valve base was prevented from deforming properly due to lack of space, like perhaps constrained by the tire beads.

It's almost certain that not all TPU stretches or expands at the same rate due to particular formulations, but the stuff definitely expands/stretches. That's how they work; it wouldn't be possible, for example, for the Schwalbe Aerothan Endurance Race TPU tubes I use on my gravel bike to be sized for tires 28mm to 35mm if they didn't expand. RideNow spec even wider tire size ranges, e.g. 18mm-32mm.

It should go without saying that, like with butyl, the lighter tube weights are largely achieved by making the tube material thinner. Some weight distinction between brands is due to TPU formulation and valve type, but I've not seen those variations within a given brand. Anyway, I think it logically follows that the thinner the material, the more vulnerable it becomes to reaching its limits. In this particular case with the weird stretching at the valve base, I've pulled some of the 36g RideNow out of 28mm tires in wide 23mm IW rims, and they did not display that kind of deformation at the valve base. Better construction? Properly sized to rim internal width? Heavier material? I dunno. I replaced the old butyl tubes in those 13c rims, so I don't have a the direct comparison with the 36g RideNow in that specific application I'd need to say more.

Bafanguy

No, mine didn't have that crater. My hole was like 8" away from the valve on the rim side, and it wasn't a tiny pinhole, it was a hole @ 2mm wide , almost like a tear. I chalked it up to a defect with the tpu material. There was no debris on or in my tyre, and my tube was the right size for my tyre. And I did not overinflate it.

cyccommute 

It is still likely to be due to the lack of stretch of TPU and/or a tube that is too small. TPU tubes need to be matched to the tire size much more carefully than butyl tubes are. Inside a tire, you shouldn’t be able to over-inflate the tube since it is constrained inside the tire. The tire will stretch a little but not very much.

I’ve experienced similar tears in butyl tubes up to a blowout due to a tear on the inside of the tube because I was using undersized butyl tubes. Here’s what I wrote on the issue a couple of years ago. TPU would be even worse since it doesn’t stretch.

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.

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