Cause of big splits in tubes?
10-12-24 | 02:29 PM
#2
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I've had two identical tube failures within a few days of each other, consisting of a big split and a little deformation next to the split. These tubes were in different wheels. I can't see anything wrong with the rim tape in either wheel. Cloth tape in one rim, plastic in the other. I've had the wheels and tubes for quite a while without any problems. The splits were on the rim side of the tubes. I didn't over-inflate the tires (about 50 PSI for tires rated for 65). Neither happened while riding.
10-12-24 | 03:15 PM
#6
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Or something in the 'molding' of the tube in that area leads to weakness.
10-12-24 | 03:39 PM
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Pinched by the tire? They are both wire bead tires and I had just mounted both (they are old but different sizes and I wanted to check to see what clearances my frame has, so I took them off and put them back on again without riding). I didn't use levers to install them. The tires are very old, the tubes probably are too but I'm not sure.
Last edited by Roundis; 10-12-24 at 04:09 PM.
10-12-24 | 04:51 PM
#8
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Pinched by the tire? They are both wire bead tires and I had just mounted both (they are old but different sizes and I wanted to check to see what clearances my frame has, so I took them off and put them back on again without riding). I didn't use levers to install them. The tires are very old, the tubes probably are too but I'm not sure.
10-12-24 | 05:05 PM
#9
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From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
tube was pinched between the rim bead area and the tire bead... you inflated the tube and it got tighter... it then blew out.
next time. inflate the tube ever so slightly so that it takes on a rounded appearance, but is still fairly soft... it only takes a few pump strokes... then insert the tube into the tire....once the tire beads are inside the rims' lips, add a few more pump strokes.. then Grab the tire with Both Hands and Twist it Side-To-Side in 6 to ten places around the circumference of the Tire... this gives that pesky tube an opportunity to behave as it should!.. continue pumping until desired pressure is achieve, and check that the tire has fully seated into the rim lips.
i do this EVERY Time i mount a Bicycle tire up... and i dismount/mount up a Lot of tires here.... two just rolled out the door 15 minutes ago...
next time. inflate the tube ever so slightly so that it takes on a rounded appearance, but is still fairly soft... it only takes a few pump strokes... then insert the tube into the tire....once the tire beads are inside the rims' lips, add a few more pump strokes.. then Grab the tire with Both Hands and Twist it Side-To-Side in 6 to ten places around the circumference of the Tire... this gives that pesky tube an opportunity to behave as it should!.. continue pumping until desired pressure is achieve, and check that the tire has fully seated into the rim lips.
i do this EVERY Time i mount a Bicycle tire up... and i dismount/mount up a Lot of tires here.... two just rolled out the door 15 minutes ago...
Last edited by maddog34; 10-12-24 at 09:11 PM.
10-12-24 | 06:22 PM
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10-12-24 | 06:48 PM
#12
A very long shot, but: if you haven't already done so, check the tire sidewall and the rubber enclosing the bead for a split. Occasionally, a brake pad that's just a bit too high in the arm (or that has worn enough to arc upward into the tire) can wear into the tire.
10-13-24 | 01:16 AM
#13
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tube was pinched between the rim bead area and the tire bead... you inflated the tube and it got tighter... it then blew out.
next time. inflate the tube ever so slightly so that it takes on a rounded appearance, but is still fairly soft... it only takes a few pump strokes... then insert the tube into the tire....once the tire beads are inside the rims' lips, add a few more pump strokes.. then Grab the tire with Both Hands and Twist it Side-To-Side in 6 to ten places around the circumference of the Tire... this gives that pesky tube an opportunity to behave as it should!.. continue pumping until desired pressure is achieve, and check that the tire has fully seated into the rim lips.
i do this EVERY Time i mount a Bicycle tire up... and i dismount/mount up a Lot of tires here.... two just rolled out the door 15 minutes ago...
next time. inflate the tube ever so slightly so that it takes on a rounded appearance, but is still fairly soft... it only takes a few pump strokes... then insert the tube into the tire....once the tire beads are inside the rims' lips, add a few more pump strokes.. then Grab the tire with Both Hands and Twist it Side-To-Side in 6 to ten places around the circumference of the Tire... this gives that pesky tube an opportunity to behave as it should!.. continue pumping until desired pressure is achieve, and check that the tire has fully seated into the rim lips.
i do this EVERY Time i mount a Bicycle tire up... and i dismount/mount up a Lot of tires here.... two just rolled out the door 15 minutes ago...
10-13-24 | 06:37 AM
#15
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The tube could be pinched at any spot depending on if it was twisted when installing. Not unusual. You may never know if your tube was pinched or not in this case but just pay attention when you mount your next tire. If this happens again after you carefully check that the tube isn't caught under the bead when installing another tube let us know. The fact that it was two tubes mounted on two different wheels with different rim strips and tires suggests that it probably wasn't some other cause.
10-13-24 | 09:37 AM
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10-13-24 | 09:53 AM
#17
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From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
except that the blow out splits and bubbled areas are extremely close to each other in both pics, indicating that, if they WERE from a rim strip problem, they would have to come from a 72+ spoke double walled low rider rim... or maybe a 48 spoke double walled rim... neither of which exist in the real world.
10-13-24 | 10:00 AM
#18
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except that the blow out splits and bubbled areas are extremely close to each other in both pics, indicating that, if they WERE from a rim strip problem, they would have to come from a 72+ spoke double walled low rider rim... or maybe a 48 spoke double walled rim... neither of which exist in the real world.
But thanks for suggesting that blowouts above the rimstrip don't involve the rim strip so the OP doesn't look at the rim strip.
10-13-24 | 10:07 AM
#19
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Your problem is due to the way that tubes inflate and (likely) due to less stretch of modern tubes. Here’s my take on the problem after many flats and a lot of thinking about the problem.
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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Dreamin' of Bemidji Down the Mississippi (in part)
Plan Epsilon Around Lake Michigan in the era of Covid
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!
Stuart Black
Dreamin' of Bemidji Down the Mississippi (in part)
Plan Epsilon Around Lake Michigan in the era of Covid
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!
10-13-24 | 10:37 AM
#21
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From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
By way of Reviewing what you have ignored... "I've had two identical tube failures within a few days of each other, consisting of a big split and a little deformation next to the split. These tubes were in different wheels. I can't see anything wrong with the rim tape in either wheel. Cloth tape in one rim, plastic in the other. I've had the wheels and tubes for quite a while without any problems. The splits were on the rim side of the tubes. I didn't over-inflate the tires (about 50 PSI for tires rated for 65). Neither happened while riding"
10-13-24 | 10:47 AM
#22
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or maybe, one time in Band Camp, maybe the, the rider skidded really hard, and.,and, and...
By way of Reviewing what you have ignored... "I've had two identical tube failures within a few days of each other, consisting of a big split and a little deformation next to the split. These tubes were in different wheels. I can't see anything wrong with the rim tape in either wheel. Cloth tape in one rim, plastic in the other. I've had the wheels and tubes for quite a while without any problems. The splits were on the rim side of the tubes. I didn't over-inflate the tires (about 50 PSI for tires rated for 65). Neither happened while riding"
By way of Reviewing what you have ignored... "I've had two identical tube failures within a few days of each other, consisting of a big split and a little deformation next to the split. These tubes were in different wheels. I can't see anything wrong with the rim tape in either wheel. Cloth tape in one rim, plastic in the other. I've had the wheels and tubes for quite a while without any problems. The splits were on the rim side of the tubes. I didn't over-inflate the tires (about 50 PSI for tires rated for 65). Neither happened while riding"
Or, the OP can take ALL the suggestions and evaluate them equally since they are don't know everything. Which is why I suggested looking more carefully at the rim strips - how they cover, how wide and how well they stay in place.
10-13-24 | 11:50 AM
#23
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From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
as to how you got two pinches in such a short time span... over-confidence and/or in a hurry....
or just bad luck...
sadly, i suffer from both afflictions, at times...
Tip for the greater good here... when levering on or off a tire, i work in Smaller Bites... never more than about 4", 10cm between lever positions... and i NEVER over-rotate the lever in an attempt to "push more bead on faster"... over-rotating the lever Can Cause Pinched Tubes... the tube can get trapped between the tip of the lever and the center valley of the rim..... Inserting the lever's tip TOO FAR into the situation can create the Same Problem.
I once pinched a tube Three Times in a row... an old Steel Sportster Harley rear wheel, and a Goodyear "Rim Saver" tire... total sweat fest, customer waiting, a hot summer Saturday morning.... and, being a Saturday, i was the only mechanic in the store... and that darn phone is jingling away, non-stop.. "Service, Line Two and Three.".. Goodyear Rim savers are the WORST tires to change a tube in... they are nearly impossible to mount, and resist efforts to collapse them into the rim valleys... which are Way too shallow on old chrome Sportster wheels...
A year or so later i had the distinct pleasure of hanging that insanely inflexible Goodyear on a fence post at the Washougal MX Park.
Last edited by maddog34; 10-13-24 at 12:09 PM.
10-13-24 | 12:48 PM
#24
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From: Denver, CO
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or maybe, one time in Band Camp, maybe the, the rider skidded really hard, and.,and, and...
By way of Reviewing what you have ignored... "I've had two identical tube failures within a few days of each other, consisting of a big split and a little deformation next to the split. These tubes were in different wheels. I can't see anything wrong with the rim tape in either wheel. Cloth tape in one rim, plastic in the other. I've had the wheels and tubes for quite a while without any problems. The splits were on the rim side of the tubes. I didn't over-inflate the tires (about 50 PSI for tires rated for 65). Neither happened while riding"
By way of Reviewing what you have ignored... "I've had two identical tube failures within a few days of each other, consisting of a big split and a little deformation next to the split. These tubes were in different wheels. I can't see anything wrong with the rim tape in either wheel. Cloth tape in one rim, plastic in the other. I've had the wheels and tubes for quite a while without any problems. The splits were on the rim side of the tubes. I didn't over-inflate the tires (about 50 PSI for tires rated for 65). Neither happened while riding"
The only difference to what I experienced and what Roundis experienced is that mine all occurred while riding.
__________________
Stuart Black
Dreamin' of Bemidji Down the Mississippi (in part)
Plan Epsilon Around Lake Michigan in the era of Covid
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!
Stuart Black
Dreamin' of Bemidji Down the Mississippi (in part)
Plan Epsilon Around Lake Michigan in the era of Covid
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!
10-13-24 | 01:05 PM
#25
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My experience has been similar. I kept getting flats on the inner side of the tube towards the rim strip. Changes of the rim strip had no effect and it was happening on multiple bikes. It wasn’t until I had an internal blowout as detailed in my post above, that the light bulb finally went off. The tube in that instance did not blow the tire off the rim. When I stopped, I had to use my tire levers to remove the tire and I heard an audible report when the tube blew, although it was somewhat muffled.
The only difference to what I experienced and what Roundis experienced is that mine all occurred while riding.
The only difference to what I experienced and what Roundis experienced is that mine all occurred while riding.