big problem with kenda thorn proof tubes

This is the third kenda thorn proof tube that has a hole in the valve stem I install regular thinner tube and I never get the problem it seemed when I installed the tube it wouldnt inflate as fast so I increased the psi to the tire recommended psi and the slack between the tire and tube was fixed but at lower psi it does not seem like it will fix itself the valve hole on the rim I always check and it was fine I will have to check it thoroughly this time. All times the hole on the tube has been at the base of the stem at the transition point and I always make sure the shrader valve is fitted properly with proper psi added the valve did not rotate over was brand new used for one mile. I will cut the tube up and use as a tire liner, I have 2 of them third one is in the pile such a shame another $15 wasted it held air for a few days when I was not riding it but did not last 1 mile bought from national department store not ebay looks the same as the pic “Fool me once, shame on you. Fool me twice, shame on me. Fool me three times, shame on both of us.”

Basically, you are getting old stock. Fresher the better. If you put a 2" tube in a big fat 2.5" tire, it can make this problem worse.

calab said:

“Fool me three times, shame on both of us.”

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Doesn't sound quite right, but maybe extrapolate to fool me ten times so I can see where this is headed (shame on my parents or the government?).

I have thick slime tube that break at the base of the valve stem I use gasket cinch and put it on my tire and rim and it seemed to help a bit but I got 4000 watts. Plus I got a staple in my Maxus slime tube combo and it let the air out. be so went to the gas station filled it up it work for a mile it all the air went out . A staple

https://bicycles.stackexchange.com/questions/9929/tube-constantly-getting-punctured-near-the-valve#:~:text=The%20tire%20slipping%20on%20the%20rim%20is%20generally,where%20rubber%20does%20not%20grip%20the%20rim%20well.

This is partly why I like to oversize my tubes. A tube that is not distended is less likely to do this, among other things.

The Kenda presta valve tubes I have run have never had this problem. The Sunlites thornproofs, on the other hand, are notorious for it. It could easily just be a function of the manufacturer switching who they get the tubes from. I've opened boxes up with different labels on the outside and surprise its got the same ink and markings on the tube as a different brand. Duro and Sunlite for instance. Green ink. IIRC its a Thai factory. Innova? Been awhile since I looked at one.

That is an option I thought about drilling the valve hole an extra 0.0625 or 0.125 over but I literally have never had any valve break on the same rim that I have had for years now except on those kenda thorn proof tires which do seem to have a slightly wider diameter valve stem as it takes more wiggling pressure to fully seat valve into hole. Its just old whether its on the retailers stocking methods or Kenda's for a major account for nationwide retailer or a combo of both. Kenda does sell a slime version normal tube which I have tried but do not like it as it gunks up the valve if I ever take air out I could carry around an additive that I can add when I get low air that doesnt hold in order to get home. I have had normal tubes that have slipped with same shrader valve stem angled and never had the valve stem fail. The kenda tubes might have more girth at the base of the stem I will measure it today if I remember. Kenda thorn proof tube is 26 1.95-2.125 and tire is 26 2.00 or 2.10
Is there a date of manufacture on the tube like car tires I just took a look at it if its there it has to be decoded printed 80379 and 810101210105 raised rubber made in china kd547 d-080

calab said:

This is the third kenda thorn proof tube that has a hole in the valve stem

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It's the leak in the stem itself, or the patch at the base of the stem?

Thorn resistant tubes can be a problem in their own right. They're thicker on the outer surface to provide more of a barrier to small sharps, but that means the stretch is concentrated across the inner surface which is thinner and easier to stretch. So the outer surface is less vulnerable to damage, but the inner surface (including the valve patch) is more highly stressed and more likely to fail.

I usually recommend against add-on puncture preventives like thick tubes, sealant, or tire liners. They all have annoying drawbacks. Instead, I recommend using a tire that has all the necessary armor built into it. There are plenty of good options.

In a truly desperate goathead-plagued environment, I recommend using a second tire as a liner. Pick one with a smooth, uniform tread, a size or two smaller than the outer tire, and cut away the bead wires on the edges. Tuck it into the bigger tire and then install a normal tube.

calab said:

I have had normal tubes that have slipped with same shrader valve stem angled and never had the valve stem fail.

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The tubes don't slip, the tire slips and the tube goes with it. You need to keep the tire from slipping and right now the valve stem the only thing that's staying put.

I have had normal tires slip taking tube with it angling the valve real bad and valve stem has never been damaged so the diameter of the valve is the only other thing I can check and compare between the kenda thorn proof valve stem diameter at base in the middle and at the tip compare it to the other inner tubes I have. Tubes are always inflated to recommended psi labeled on tire. I dont know chalo but I took some pictures for everyone to view, I will get the second kenda thorn proof tube if I still have it was planning to use 2nd tube as a tire liner is that sub optimal compared to a smooth tire but better then commercial liners that have sharp corners on them. Will now use two kenda tubes as liners

Chalo said:

calab said:

This is the third kenda thorn proof tube that has a hole in the valve stem

Click to expand...

It's the leak in the stem itself, or the patch at the base of the stem?

Thorn resistant tubes can be a problem in their own right. They're thicker on the outer surface to provide more of a barrier to small sharps, but that means the stretch is concentrated across the inner surface which is thinner and easier to stretch. So the outer surface is less vulnerable to damage, but the inner surface (including the valve patch) is more highly stressed and more likely to fail.

I usually recommend against add-on puncture preventives like thick tubes, sealant, or tire liners. They all have annoying drawbacks. Instead, I recommend using a tire that has all the necessary armor built into it. There are plenty of good options.

In a truly desperate goathead-plagued environment, I recommend using a second tire as a liner. Pick one with a smooth, uniform tread, a size or two smaller than the outer tire, and cut away the bead wires on the edges. Tuck it into the bigger tire and then install a normal tube.

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That failure looks characteristic of excessive stretch at the point the valve emerges on the inside of the rim. That's what thorn-resistant tubes do, especially when they have to expand a lot to fit the tire.

It looks like the valve stopped short of being fully seated, and like 1/2" or so of valve stem was trapped inside the rim where tire pressure could inflate it along with the tube. Make sure you pull the valve all the way into its hole before you inflate the tube.

Try using a normal tube a size larger than the tire you're using. The objective is to have the least stretched tube surface when the tube meets the wall of the tire.

calab said:

I have had normal tires slip taking tube with it angling the valve real bad and valve stem has never been damaged so the diameter of the valve is the only other thing I can check and compare between the kenda thorn proof valve stem diameter at base in the middle and at the tip compare it to the other inner tubes I have.

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Maybe a little of this along the tire bead on one side of the tire to keep it from slipping, to address the slipping rather than addressing the consequences.
https://www.nashbar.com/continental-tubular-rim-cement-c16003121/p-ruaetwtqaeqeyaa2?msclkid=0cf55a232b0c128b88f23bf06499198b&utm_source=bing&utm_medium=cpc&utm_campaign=NB%20-%20Search%20-%20Dynamic%20Content%20-%20Category&utm_term=nashbar&utm_content=All%20Webpages&__cf_chl_jschl_tk__=KJFyvODWkR7vFBMDErR42tTcfy0pn3LRJ_t4IQyYdRg-1641238430-0-gaNycGzNCf0

The stretching problem is one I've encountered a few times, but I have also had a few specific "brands" that had very specific failures, some of which were valve stem ruptures (mostly at the join to the tube, base of stem, but a few were the bond between rubber on stem and the actual brass stem itself). All were schrader; this is over quite a few years.


"Brand" in this case refers to the box the tube was in when purchased, meanign the company that put their name on the box; the actual tube they use in that box changes over time (depending on the deal they get, I'm sure). So when I run into a "brand" problem, I find that most of the ones on the shelf (at least at that specific store or seller) around that time will generally have that problem...but some won't, because theyr'e newer or older batches, and may not even be the same tube manufacturer. A different location may have different stock.


The other problem I've had, like others, is me simply not airing the tube up enough, so that the tire creeps along the rim, dragging the tube with it, pulling or even yanking on the tube/stem joint and tearing it just like in your pic. I have had it happen more on front tires than rear, because of sudden braking forces, than pedal or motor torque on a drive wheel.


FWIW, I have had much better luck with CST (cheng shin tire) brand bicycle tubes and tires than Kenda. Their rubber is generally more flexible, especially in greater thicknesses, for any tire or tube I've used, and doesn't age as badly (Kendas dry rot much faster here in the desert, than the CSTs). The problem is that buying boxed tubes with "brand names" on them doesn't get you the same ones every time, and you can't know what's in the box until you open it.

It took me a while to find a good tube for my SB Cruiser's rear tires, and luckily enough the seller / brand has had the same tubes in the boxes every time I bought one (which has been much less often now that Iv'e found a good one), but I dont' expect this to be the case forever. I forgot what manufacturer they are (I think CST), the "brand" is BikeMaster.


Many tubes I've used have an actual human-readable date on them, so you can at least tell if they were old or not before you got them. If they're old, you at least have some potential warning that something could go wrong from age.

Here is the last one which the valve stayed straight when I was riding I kept the first one and I rode on it flat made the valve pop off what remained looked like an outtie belly button. First I stretch the valve, second and third I tried to get clear pictures of both ends not stretched

Mislabeling tube size has been an increasing problem in recent years. For reasons of cost, ease of install, or whatever, tubes are labeled one to three sizes above what they actually are.

If the tube you're working with doesn't look nearly the size of the cavity inside the tire you're working with, get a bigger tube.

The kenda thorn proof tube pumped up fine near the end but from 0 to 35psi the 2.00 tire had some flap until the tube reached 45psi final psi of 55 and I always check the fitment all the way around for the psi pressure and bead fitment I had a tire not seat and the tube bubbled out and popped like it was a gun learned to always look while pumping. The flat I had I did not ride and walked the bike every I needed to go then did the wimpering shameful call for a ride got my $12 for bottles which was a waste of time but well worth it for the physical activity.

Suggestion. Use standard tubes and maybe some sort of tire/tube armor that lays on top of tube inside tire?
Suggestion2: I Carry a patch kit, tube, and pump when riding in the woods. I have had two flats (nail, and pinch-flat) last year both times a non-event.

Interesting observation about the thinner top of thick tubes. The bottranger tubes I like best are thick on the top too. making them even heavier. I find that slime works better on staples if the tube is thicker. What you need depends on where you ride. My paved roads are covered in staples and screws, while in the dirt it's huge mesquite thorns. Bike flats are just one more reason I bike less these days. Of course the fire was the big discouragement. But I don't miss fixing flats twice a month.

My guess was that older tubes just lost the seal around the metal stem, causing the bubble that pops. I mean really old stock though, you can kind of smell it when they get that old. No fresh rubber smell left.

Low pressure can also let the rim nick the stem, but it would not make a hole if the stem was solidly attached to the rubber at the base. It will rip if its loose and bubbled. I do wish that bike stems more resembled the motorcycle schrader stems, which seem to be immune to the problem. The lock nut seems to help, especially if riding home on a flat. But its obviously a different method of attaching the stem. Likely no room for it on a bike tires skinny rim, unless its a presta.

dogman dan said:

...I do wish that bike stems more resembled the motorcycle schrader stems, which seem to be immune to the problem. The lock nut seems to help, especially if riding home on a flat. But its obviously a different method of attaching the stem. Likely no room for it on a bike tires skinny rim, unless its a presta.

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Schwalbe sells tubes with "AV" in their part number. Stands for "American Valve" and its a fully threaded Schrader with a locknut. I usually try to do Presta only but for the front tire on my Bullitt a Schrader worked best. The normal bicycle valves walked no matter what but the version of this valve Schwalbe uses is, as you say, immune to this problem.



I use FlatOut both as a tubeless sealant and as a sealant within tubes. Its ability to seal holes and the fact that it literally never dries out makes it essentially Slime version 2.0. I took an entire nailgun strip of 6 roofing nails in a line once on my Big Fat Dummy on a run back from Home Depot with potting soil bags... and the tire sealed back up. I had to refill it with my pump (runs off my ebike battery) three times but after #3 it stayed sealed and remains so today. Vee Snowshoe XL tires so big suckers. And they were tubeless. When I was still using tubes I pulled a jagged flat metal strip out of the same tire and the FlatOut did the job again after I think two refills.

Continental also sells fully threaded Schrader valve tubes.

In my experience, metal stemmed tubes detach at the base of the stem at least as often as rubber clad stems have problems.

Nothing to get from the measurements depends on how much pressure you put on the caliper
7.61mm at the top of the valve 8.30mm and 8.05 at the base for normal tubes
7.67mm at the top of the valve 8.10mm at the base for kenda thorn proof

Presta valve is thinner with metal valve all the way down do the shrader have the metal all the way down but rubber to me I see a black hard substance inside the cracked kenda valve where the outer rubber overlaps. I should try a thorn proof in a presta valve if any are available I dont like the adapter I have to use its just another step I leave the adapter on my pump has both shrader and presta I still leave the shrader adapter on the presta I have always like shrader over presta. The foam insersts might be option. https://flattiredefender.com/flat-tire-defender-products/ there is an ebike option.
Tannus ARMOUR looks good still uses air but uses foam to https://www.ebay.com/itm/294669168817?epid=3034162154&hash=item449ba6b0b1:g:2jUAAOSwvEFgnXAl
CushCore Foam Bike Tire Insert
Stop-A-Flat Puncture Proof, Thorn-resistant, No-flat, Bicycle Tube https://www.ebay.com/itm/383421247515?epid=1359522858&hash=item5945aff01b:g:Ix8AAOSw3F5eRtRb
Everyone loves slime or tubeless debates on both sides either love them or hate them with all their mess, no flat stiff ride no air cushion I like the smooth tire liner idea. If I normally use a 26 2.00 or 26 2.10 deep tread trail tire then should I scour the bicycle shops dumpster for 26 x 1.90 smooth tread tire and should I also shove in both or one kenda thorn proof tube cut length wise for additional tread area protection

https://endless-sphere.com/forums/viewtopic.php?f=3&t=110865&p=1625441&hilit=foam#p1625063

calab said:

I should try a thorn proof in a presta valve if any are available

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Yes, they're available. They have several modes of failure that Schrader valves don't, so they're a downgrade in that regard.

It sounds like your problems aren't related to thorns, and as I already told you, thorn resistant tubes have problems that regular tubes don't. So maybe try normal tubes and find out for yourself why they're the normal kind?

Chalo said:

In my experience, metal stemmed tubes detach at the base of the stem at least as often as rubber clad stems have problems.

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For myself, I really only use the threaded type over the rubber type because the nut holds it in place while I air it up at installation, etc., so my often-numb fingers don't have to.

calab said:

I should try a thorn proof in a presta valve if any are available

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Regarding Presta, they're not any better than Schrader, as far as my personal experience with the problem you've got, and I've had the little nut on the end that keeps the valve closed unscrew itself and lose air, and it was harder to get air pumps to correctly fit over them, and they require you carry an adapter to use common gas station airpumps, etc. So I stopped using them.

Been bicycle commuting for something like 40 years dating back to the mid- 1970's (I took about a 10 yr break thanks to a heart attack, and can thank the 'e' in 'ebike' for getting me back into daily cycling). Generally, valves don't fail unless you've got a secondary problem or human error that needs a solution. Unless of course the tube construction itself is crap and thats more common today than it used to be.

While prestas are found on all but bottom of the line bicycles, the reason they are used isn't necessarily relevant to ebikes. But in terms of reliability, they are completely a wash with Schrader. You can say Schrader is heavier, and it needs spring tension to activate whereas presta uses simple air pressure and is a simpler mech. Presta is better suited to narrower rims which for ebikers is largely meaningless.

As for Presta unscrewing and losing air, the solution to this is to not listen to the hardcore cyclists and use a cap. The whole 'the cap is useless' thing is just attitude. I like the kind that also have a valve core remover built in so I always know where it is. Screw it down right and cap it and its never a problem. Overtightening is as bad as undertightening so there's a little bit of a learning curve.

Since one is pretty much just as reliable as the other, the choice comes down to a) what kind of rims can you buy when you build your wheels and b) what kind of pumps you have. I actually prefer schrader-drilled rims. I can use adapters that do a fine job of converting to presta and in a pinch I can use a schrader tube if thats all I can lay hands on.

MoneyPit said:

While prestas are found on all but bottom of the line bicycles, the reason they are used isn't necessarily relevant to ebikes. But in terms of reliability, they are completely a wash with Schrader.

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I beg to differ. Presta valves can and do suffer loss of the stem nut, bending or breaking of the fragile inner stem, unscrewing of the valve core, and separation at the base of the valve. When aired up with a portable hand pump, they're pretty easy to break off.

90 percent of the stem-related problems I see with Schrader valves are from the user running a tire when it's almost flat, causing the valve to tilt and get cut on the edges of the rim hole. But I see Presta valve problems more often, and they're not predominantly the result of user error.

Presta valves became associated with quality bicycles back when quality bikes had narrow rims (which would have been weakened by the larger Schrader sized hole). Now that bike fashion has shifted strongly in favor of wide rims, there's no reason to keep the inferior valve, yet buyers and product managers still ignorantly associate them with quality.

Schrader valves are used all over industry wherever compressed air exists. But nobody outside the bicycle industry uses Presta valves, because they suck.