How does a tube get slit without obvious incident?
06-04-23, 06:08 PM
#1
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Thread Starter
How does a tube get slit without obvious incident?
I had a flat front tube, found a goathead on the side of the tire but not deeply embedded; there's a liner inside, too.
When I got home I found a ⅛" slit diagonally, on the bottom of the tube. I didn't notice running over anything, or hear the hiss of air I'd expect with a slit that big.
I've slit tubes in the past when I've run over a big piece of glass or metal. The event was obvious by sound and I could see damage to the tire, but I don't see that in this case.
When I got home I found a ⅛" slit diagonally, on the bottom of the tube. I didn't notice running over anything, or hear the hiss of air I'd expect with a slit that big.
I've slit tubes in the past when I've run over a big piece of glass or metal. The event was obvious by sound and I could see damage to the tire, but I don't see that in this case.
06-04-23, 06:28 PM
#2
Really Old Senior Member
How long did you ride with the tire underinflated?
Once the tire gets "squirrely", a small embedded object can open the hole wider as the tube starts moving around.
Just walking the bike with a flat starts doing bad things to a tube's integrity.
1/8" isn't worth posting about.
Once the tire gets "squirrely", a small embedded object can open the hole wider as the tube starts moving around.
Just walking the bike with a flat starts doing bad things to a tube's integrity.
1/8" isn't worth posting about.
06-04-23, 06:35 PM
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There's far too many possibilities to kill off my fingers to list. If this is, so far, a one time thing, feel free to ignore it as an example "stuff happens". If it's happened before, than more info, or photos would help.
One thing I do with all "non-puncture" leaks is to record the location with respect to the tire and/or rim, so I can more easily differentiate between bad luck and some specific cause.
Also be aware that older tubes dry out and become less supple. That makes them more likely to split or over react to penetration or strain.
One thing I do with all "non-puncture" leaks is to record the location with respect to the tire and/or rim, so I can more easily differentiate between bad luck and some specific cause.
Also be aware that older tubes dry out and become less supple. That makes them more likely to split or over react to penetration or strain.
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An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
06-04-23, 06:56 PM
#5
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06-04-23, 08:15 PM
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tube can get trapped between the tire bead and rim... it may take time to migrate out of that pinch.. when they slip out, they can and do get slits in them.
i ALWAYS pre-air the tube to a round state... Just enough to get them to that shape... Then slide them into the tire, Then put the tire on the rim... THEN Add air up to about 7 lbs. and TWIST the tire side to side to help bead the tire and Free The Tube if it's pinched....... this all goes very quickly once you've done it a couple thousand times... and it sure beats Re-Patching the tube....
i ALWAYS pre-air the tube to a round state... Just enough to get them to that shape... Then slide them into the tire, Then put the tire on the rim... THEN Add air up to about 7 lbs. and TWIST the tire side to side to help bead the tire and Free The Tube if it's pinched....... this all goes very quickly once you've done it a couple thousand times... and it sure beats Re-Patching the tube....
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06-04-23, 08:49 PM
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I usually patch and reuse tubes. One plus is that if I get another flat the same distance from the valve that is a flag that there is a rim or tire issue at that exact distance from the valve. Makes finding the cause so much easier when you only need to look at 1' of tire/rim in two places. (Always mount your tires with the label in the same spot relative to the valve; either centered at the valve or exactly opposite.)
06-04-23, 08:59 PM
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I posted this in another tire thread this morning - the easy way to pre-inflate tubes to the proper pressure for inserting into tires. By mouth and lung power. Your hardest blow will be just perfect. On some very tight tires, I have to drop some of that air out to get the last few inches of bead on. Doing that pre-inflate has saved me who knows how many pinch flats and always makes the operation simply easier. (I'm lucky. I grew up in a home with cats, horses and siblings that was far, far from "germ-free". Nothing on an innertube is going to phase my immune system. I bet a Wet Nap would work for those not so blessed.)
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06-05-23, 06:36 AM
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How's the rim strip/tape? If by "bottom" of tube you mean toward the hub, it sounds like a spoke hole or unprotected spoke head, depending on rim style.
06-05-23, 09:02 AM
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Welcome to the club! It’s probably the least exclusive club in the history of clubs, however. At this point it includes about 3/4ths of the world’s population. It’s probably easier to count the number of people not in the club.
You are entirely correct, however. Any tube damage that releases air is cause for concern. Saying otherwise is a bit of a head scratcher.
You are entirely correct, however. Any tube damage that releases air is cause for concern. Saying otherwise is a bit of a head scratcher.
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Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
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Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
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06-05-23, 09:09 AM
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I had a flat front tube, found a goathead on the side of the tire but not deeply embedded; there's a liner inside, too.
When I got home I found a ⅛" slit diagonally, on the bottom of the tube. I didn't notice running over anything, or hear the hiss of air I'd expect with a slit that big.
I've slit tubes in the past when I've run over a big piece of glass or metal. The event was obvious by sound and I could see damage to the tire, but I don't see that in this case.
When I got home I found a ⅛" slit diagonally, on the bottom of the tube. I didn't notice running over anything, or hear the hiss of air I'd expect with a slit that big.
I've slit tubes in the past when I've run over a big piece of glass or metal. The event was obvious by sound and I could see damage to the tire, but I don't see that in this case.
I might have agreed even a few months ago. However, nearly every flat I’ve experienced over the last year have been on the interior of the tube…i.e. the rim side. I’ve changed rim strips from cloth Velox just in case there was something in the tape. I marked the tube with direction arrows and clocked my tubes to the label. Nothing seemed to work. I still experienced internal pinhole flats.
About a month ago, I went through flat hell in Wisconsin and Michigan while on tour. I experienced 8 to 10 flats of exactly the same kind including 4 in a single day. One of them was on one of the few really nice downhills in the U.P. in Michigan. I did a quick dodge around rumble strips to get out into the lane rather than do 20+ mph on a very narrow shoulder. The picture below is typical of Michigan’s rumble strips.
I experienced a blow out…which is very scary on a loaded touring bike at normal speed and petrifying at high speed. But it wasn’t a normal blowout…i.e. tire coming off the rim. The tire was still securely attached to the rim. When I took the tire off, there was a rip on the inside of the tube about an inch long. After changing my bike shorts (
), a light bulb went off. There is no way that I could have had anything inside the tire that would cause the tube to actually rip. I eventually decided that what had happened was that the quick steering to avoid the rumble strips had allowed the tube to be pulled too far in one direction. The rubber was obviously thin on the rim side and it tore due to the extra force on the rubber.
I have, in the past, been a proponent of using smaller tubes. They are lighter to carry and rubber expands to fill the space. I didn’t, however, take into account something that I’ve noticed when pumping up a tube outside of the tire. Tubes tend to expand more on the outside of the torus that is the tube than on the inside of the torus. If the tube were a straight pipe, the pressure expansion would look a bit like this (please excuse the extremely simple drawings). The pressure would expand equally in all directions and the tube (pipe, actually) would expand equally in all directions.
But in a torus shape, the outside edge expands slightly more than the inner edge like in the diagram below. The inner edge doesn’t have room to expand as much as the outer edge…it packs up a bit more. You can observe this when you pump up the tube outside of the tire.
Now think of the tube in the rim, especially if the tube is a smaller sized tube. When the tube is put in the tire and filling is started, the tube expands towards the tire first. Then as the tube fills, it expands into the rim channel. The outer part of the tube is trapped against the tire and the inner part has to expand into the channel where it thins. I suspect (but can’t really prove) that the tube thins a lot and, rather than the tube being punctured, the tube tears and creates a pin hole.
Here’s a better representation of the cross section. The tube expands towards in the direction of the red arrows first… especially at low pressure…then it expands in the direction of the green arrow as the pressure increases. The part of the tube trapped at the “bottom” of the tube stretches more and thins leaving it prone to tearing.
My solution was to replace my 23/28mm tubes with 38/44mm tubes. The wider tubes had more material in the channel and were less prone to tearing. The proof of this idea was that my inner punctures disappeared at about the 1/2 way point of my 1200 mile tour.
Going forward, I’m going to stop using small diameter tubes and use wider ones.
About a month ago, I went through flat hell in Wisconsin and Michigan while on tour. I experienced 8 to 10 flats of exactly the same kind including 4 in a single day. One of them was on one of the few really nice downhills in the U.P. in Michigan. I did a quick dodge around rumble strips to get out into the lane rather than do 20+ mph on a very narrow shoulder. The picture below is typical of Michigan’s rumble strips.
I experienced a blow out…which is very scary on a loaded touring bike at normal speed and petrifying at high speed. But it wasn’t a normal blowout…i.e. tire coming off the rim. The tire was still securely attached to the rim. When I took the tire off, there was a rip on the inside of the tube about an inch long. After changing my bike shorts (
), a light bulb went off. There is no way that I could have had anything inside the tire that would cause the tube to actually rip. I eventually decided that what had happened was that the quick steering to avoid the rumble strips had allowed the tube to be pulled too far in one direction. The rubber was obviously thin on the rim side and it tore due to the extra force on the rubber.I have, in the past, been a proponent of using smaller tubes. They are lighter to carry and rubber expands to fill the space. I didn’t, however, take into account something that I’ve noticed when pumping up a tube outside of the tire. Tubes tend to expand more on the outside of the torus that is the tube than on the inside of the torus. If the tube were a straight pipe, the pressure expansion would look a bit like this (please excuse the extremely simple drawings). The pressure would expand equally in all directions and the tube (pipe, actually) would expand equally in all directions.
But in a torus shape, the outside edge expands slightly more than the inner edge like in the diagram below. The inner edge doesn’t have room to expand as much as the outer edge…it packs up a bit more. You can observe this when you pump up the tube outside of the tire.
Now think of the tube in the rim, especially if the tube is a smaller sized tube. When the tube is put in the tire and filling is started, the tube expands towards the tire first. Then as the tube fills, it expands into the rim channel. The outer part of the tube is trapped against the tire and the inner part has to expand into the channel where it thins. I suspect (but can’t really prove) that the tube thins a lot and, rather than the tube being punctured, the tube tears and creates a pin hole.
Here’s a better representation of the cross section. The tube expands towards in the direction of the red arrows first… especially at low pressure…then it expands in the direction of the green arrow as the pressure increases. The part of the tube trapped at the “bottom” of the tube stretches more and thins leaving it prone to tearing.
My solution was to replace my 23/28mm tubes with 38/44mm tubes. The wider tubes had more material in the channel and were less prone to tearing. The proof of this idea was that my inner punctures disappeared at about the 1/2 way point of my 1200 mile tour.
Going forward, I’m going to stop using small diameter tubes and use wider ones.
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Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
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!
Days of Wineless Roads. Bed and Breakfasting along the KATY
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Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
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!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
Last edited by cyccommute; 06-05-23 at 09:49 AM.
06-05-23, 02:17 PM
#12
Senior Member
Thread Starter
After I patched the slit, I looked for more leaks, because this tube had been losing air more quickly than my rear for a while. I found 15 pinhole leaks before I stopped looking. So I chalk this up to a defective tube.
06-05-23, 02:38 PM
#13
Really Old Senior Member
Or oriented in certain areas?
I had a very old? tube once that started "sprouting" pinholes upon airing it up after patching a minor hole.
It was like little spots had "carbonized", getting "brittle". The tube would stretch a bit and they didn't.
It was in the area of the patch where the tube didn't expand evenly because of the additional patch thickness.
06-05-23, 10:41 PM
#14
Senior Member
Thread Starter
I always pre-inflate to make sure the tire's in the rim.
Randomly all over the tube. I found them 1 or 2 at a time. I always check for more leaks after fixing the first. Smaller leaks won't show when there's a large one. I patched 12 on this tube (in this session; it already had 5 old patches.) before I gave up when I found 3 more after the 12th. I run the whole tube through soapy water each time, so these leaks must have sprung when I inflated the tube.
It was a new tube. I've never had a tube as old as you described.
06-06-23, 07:31 AM
#15
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As for the pin holes, are they all in the same place or close to it? Goatheads can get through the liner and the tube can squirm a bit while you ride especially if the tire is deflating. This can result in clusters of pinholes. You should also check your liner for anything left in the liner itself as well as the inside of the tire. I try to flick out all of the ends of goatheads that I see in the tire to keep them from being pushed through to the tube as the tire rolls.
By the way, I never preinflate. Tires are easier to put on the rim if there isn’t any air in the tube.
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Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
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!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
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!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
06-07-23, 04:59 PM
#16
Senior Member
Thread Starter
I preinflate to insert the tube in the tire, then deflate, then inflate a little after I have the tire mounted to make sure it's mounted properly, sometimes have to deflate to correct.
