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-   -   Tube/patching question (https://www.bikeforums.net/bicycle-mechanics/356708-tube-patching-question.html)

mwrobe1 10-25-07 07:49 AM

Tube/patching question
 
OK...for the record...I used the search function first...but no success.

So here goes...

I get a chance to actually go out and ride BESIDES commuting to work. Get out to the garage...rear tire is flat. Puncture is from the rim side of the tire and I notice that the cheap rubber rim strip pushed itself into the spoke hole (I have doublewall rims) and it happens to be the "first" spoke hole that is next to the stem. OK fine...I patch the tube and I cut a section from another patch and rubber cement it to the rim strip to cover the "rip". Pump it up to 90psi...in 5 minutes....PSSSSSSSSSSSSSTTTTTTTTT!

So I take the tube off the rim again, pump it up...keep pumping...keep pumping...I can't find the LEAK! WTF? (I didn't measure pressure this time for what its worth)

Anyway...I plan on getting a couple new tubes and new rim tape...that should solve the problem and save my time from fiddly *ucking around with it.

But the practical side of me has a couple of questions:

I noticed, when I was pumping up said tube off of the rim, that there was significant bulging around the stem area...is that normal?

How close to the stem is it acceptable/functional to patch a tube?

What could POSSIBLY cause a tube (that is installed) to accept 90psi for five minutes and flat and show no signs of leakage when its off the rim?

SoonerBent 10-25-07 08:11 AM


Originally Posted by mwrobe1 (Post 5518118)
I noticed, when I was pumping up said tube off of the rim, that there was significant bulging around the stem area...is that normal? Perfectly normal.

How close to the stem is it acceptable/functional to patch a tube?There is a raised area where the stem bonds to the tube. Anywhere off of that area is fair game for patching. In a pinch I've patched half on/half off of the raised area, patches just don't seem to form as well over the contours of that area.

What could POSSIBLY cause a tube (that is installed) to accept 90psi for five minutes and flat and show no signs of leakage when its off the rim. The tube outside the tire has very little pressure, it's the constraint of the tire/rim that creates pressure. A small leak will show up if you use water to find it but will take a long time to leak down on a bare tube.?

..

MichaelW 10-25-07 11:20 AM

Check your rim for sharp edges (remove with emery cloth) and spokes that are too long and protruding into the tube..
Use Velox cloth tape.
Most of us slip in a replacement inner and patch the tube later.

GCRyder 10-25-07 01:38 PM


Originally Posted by mwrobe1 (Post 5518118)
I noticed, when I was pumping up said tube off of the rim, that there was significant bulging around the stem area...is that normal?

What could POSSIBLY cause a tube (that is installed) to accept 90psi for five minutes and flat and show no signs of leakage when its off the rim?

1) Yes, the bulging is normal. 2) When you pump a tube that's not confined by a tire, adding air increases volume (hence the bulging), but pressure doesn't go up much. The valve itself could be leaking, but you can't get enough pressure to make it leak when the tube's not inside the tire.

twobikes 10-25-07 01:44 PM

I have had a tube leak because the valve core had come just a tiny bit loose without being related to your other leak. It is always good to check how tightly it is turned into the stem.

Air 10-25-07 10:59 PM


Originally Posted by mwrobe1 (Post 5518118)
OK fine...I patch the tube and I cut a section from another patch and rubber cement it to the rim strip to cover the "rip". Pump it up to 90psi...in 5 minutes....PSSSSSSSSSSSSSTTTTTTTTT!

<snip>

What could POSSIBLY cause a tube (that is installed) to accept 90psi for five minutes and flat and show no signs of leakage when its off the rim?

Arrrrggh - this JUST happened to me. On my folder the tires are impossible to get off and almost impossible to get back on. 45 mins later I finish up, spend a few minutes getting ready for bed, and PPppppssssssssssssttttttttttt. Apparently I'm taking my other bike tomorrow cause I'm just plain done tonight.

[note - on all my other bikes I can patch a flat and in 10 mins I'm back and going. I can't get these freakin' tires off without a lever which always puts a hole in the tube. Sigh... ]

WNG 10-27-07 03:32 AM

Ah, used to have such problems with Specialized S and R kevlar folders on Italian clincher rims. I just couldn't rolled them on by hand. Must do it with irons, and they were those Al Specialized tube killers.
:D

What you can do is make yourself and little helper from coated wire hangers. Cut a length, grind any sharp edges off, and bend and loop it to tuck under the bead to push the tube clear of the irons.

froze 10-27-07 08:42 AM


Originally Posted by WNG (Post 5530387)
Ah, used to have such problems with Specialized S and R kevlar folders on Italian clincher rims. I just couldn't rolled them on by hand. Must do it with irons, and they were those Al Specialized tube killers.
:D

What you can do is make yourself and little helper from coated wire hangers. Cut a length, grind any sharp edges off, and bend and loop it to tuck under the bead to push the tube clear of the irons.

This is very bad advice, I've never had this issue, I've used and still use Specialized folders on Torelli rims. I also can't recommend a coated wire hanger even if you grind off sharp edges, this is only something a real beginner would do only to find out they'll eventually puncture a tube! If you put just a little air in the tube to just hold a shape instead of leaving it completly flat when reapplying the tire you won't have to use such cheap tricks and risk ruining a tube.

If you don't believe me and or want more detail see this: http://www.parktool.com/repair/readhowto.asp?id=100

Air 10-27-07 09:15 PM

Thanks for the tips - I always do put a little air in the tire. It's getting them off in the first place that's more of a problem; I really have to dig to get under the bead and so almost every time it grabs the tube along with the tire, Never had a problem on any other tire - just these.

WNG 10-28-07 02:12 AM


Originally Posted by froze (Post 5530981)
This is very bad advice, I've never had this issue, I've used and still use Specialized folders on Torelli rims. I also can't recommend a coated wire hanger even if you grind off sharp edges, this is only something a real beginner would do only to find out they'll eventually puncture a tube! If you put just a little air in the tube to just hold a shape instead of leaving it completly flat when reapplying the tire you won't have to use such cheap tricks and risk ruining a tube.

If you don't believe me and or want more detail see this: http://www.parktool.com/repair/readhowto.asp?id=100

Ummm, OK.
How do you know this is such bad advice when you've never come across such a problem? When you do, then put in your $0.02 on your solution. It worked for your Torelli rims...that doesn't mean it's a walk in the park with other makes. I had trouble just like Air stated, long ago with Ambrosio Durex Elite, early Campy and Specialized R 700x19mm tires. There wasn't a lot of casing to work with. 9 times out of 10, it wasn't going to mount by hands alone. On the road especially, all you have are your tire irons. The semi-inflated tube needs to be clear of the iron to not get pinched. One can't fit a finger in there. That's where the blunt bendable wire tool comes in to just lift the tube clear as you start prying the bead on.
In this case, it was to prevent the tube being caught and punctured.
Not every solution requires an expensive over-engineered device.
But if it must be a chromed, blue-handled tool designated PBTI-01 (Blunt Tube Instrument) to justify and make you feel good inside, then whatever floats your boat.
;)
What I deem as real beginner is applying generic (albeit good) advice for general situations and attempt to "hammer a square peg into a round hole" only to find it doesn't work for all cases.

mwrobe1 10-28-07 06:25 AM

For the record...

I got Velox rim tape and one new tube (um...why do they charge $6.50 for a @#$damn tube) and went on a nice 20 mile jaunt yesterday...no problems. :)

Thanks to all for chiming in.

freako 10-28-07 07:46 AM


Originally Posted by WNG (Post 5534453)
Ummm, OK.
How do you know this is such bad advice when you've never come across such a problem? When you do, then put in your $0.02 on your solution. It worked for your Torelli rims...that doesn't mean it's a walk in the park with other makes. I had trouble just like Air stated, long ago with Ambrosio Durex Elite, early Campy and Specialized R 700x19mm tires. There wasn't a lot of casing to work with. 9 times out of 10, it wasn't going to mount by hands alone. On the road especially, all you have are your tire irons. The semi-inflated tube needs to be clear of the iron to not get pinched. One can't fit a finger in there. That's where the blunt bendable wire tool comes in to just lift the tube clear as you start prying the bead on.
In this case, it was to prevent the tube being caught and punctured.
Not every solution requires an expensive over-engineered device.
But if it must be a chromed, blue-handled tool designated PBTI-01 (Blunt Tube Instrument) to justify and make you feel good inside, then whatever floats your boat.
;)
What I deem as real beginner is applying generic (albeit good) advice for general situations and attempt to "hammer a square peg into a round hole" only to find it doesn't work for all cases.

I happen also to agree with Froze, that was bad advice. I've been riding a long long time, since I was 16 and I'm now 70 and still ride on long distance tours as well as short tours and even races and triathlons (where one person runs, another swims, and another rides-I do the riding), and never have I or anyone I've ever known needed to use a coat hanger to stuff a tube into a tire and I've installed some dam tough tires over the years. That was very bad advice coming from an obvious amateur no matter what spin you put on it.

operator 10-28-07 08:36 AM


Originally Posted by WNG (Post 5534453)
Ummm, OK.
How do you know this is such bad advice when you've never come across such a problem?.

Sorry man, it's not that great of advice unless you are stuck in antarctica with only a coat hanger to fix your flat to get yourself back to civilization.

Correct tire seating procedure, some soapy water and a good set of park tool levers is all you should ever need to do it properly. Metal objects coated or not risk puncturing the tire, tube and gouging the rim.

soma2x 10-28-07 03:07 PM

I've never been able to use tire irons without either breaking the tire iron or putting a hole in the tube. Get yourself a Kwikstik. For me they're like magic. I also notice that for skinny tires (my 28s and 32s), its best to leave the tube completely uninflated and tuck the tube into the tire as you work the bead over the rim. For bigger tires (my 37s), inflating the tube to shape works better. Good luck

operator 10-28-07 03:23 PM


Originally Posted by soma2x (Post 5536331)
Get yourself a Kwikstik.

Those were designed for 26" tires, and don't work very well for tight rim/tire combos due to the size of the head. Park TL-1's will work where the quickstick fails.

zonatandem 10-28-07 03:28 PM

Build up some thumb muscle . . .

DannoXYZ 10-28-07 04:57 PM

Uh... don't use rubber-cement. Vulcanizing fluid is what you want, it actually melts the rubber together.

And coat-hangers? Is this the Ghetto Bike Works? Tools designed specifically for tyre-changing works a lot better and safer for the tube too...

Air 10-28-07 08:27 PM

As I tried to find and fix the hole it blew up in face. Good riddance :D


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