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How did I knacker this inner tube?

JameyJamey Posts: 2,152
edited April 2010 in Workshop
*** Long, boring post alert - you might want to go and fetch a tasty beverage before reading ;) ***

First off let me say that I've been patching inner tubes for years and if I'm completely honest I'm actually a little bit proud of my patching abilities. Every single one I've done up until tonight has been nigh-on perfect - firmly stuck down all the way around, no peeling and they've all gone on first time, no need to 'touch up' the rubber cement or anything.

Until tonight.

I've just tried to patch a tube and it was an absolute bloody nightmare and I think I've ended up knackering the tube (will come back to that at the end).

So if I post the full story here, would some of you chaps be kind enough to have a read and perhaps answer my questions and see if there's anything obvious I've done wrong?

Ok, here's the story.

I had a flat this morning so swapped the tube for a fresh one and put the punctured tube in my bag to mend at home this evening. Fast forward to this evening and I've gott all my stuff ready to begin the process.

I submerged the tube in water to find the leak and made a note of it (was quite hard to find outside of the water as it closed up perfectly and was completely invisible). Then I dried that area of the tube thoroughly and went over it lightly with the sandpaper from the kit.

The hole was right next to a seam so I knew I'd have to go over the top of the seam with the patch but I've done this before no problem.

I applied the rubber cement to the area of the tube, applied a little more to the patch and stuck the two together. Pressed hard with my thumbs and held it for a little while. As soon as I released the pressure (ready to leave it to set properly) the patch came away.

I was a bit surprised as this is a repair kit I've used before so I know everything's fine. the only thing difference was the brand of tube - in the past I've always had Specialized tubes but this was a Schwalbe one.

Anyway I discarded the patch and went over the area again with the sandpaper. Once done I went for a new patch but I'd run out of the small patches so I had to go for the next size up which are sort of oblong-shaped with rounded corners. Too big to fit entirely within one 'side' of the tube but it's all I had.so I did the same again.

This time when I released thumb pressure the middle part was stuck but the coloured, feathered edges of the patch were peeling up a bit... At this point I just wanted to finish the job so I jammed some more rubber solution under the peeling bits and went back to applying pressure a bit longer.

I noticed at this point that the rubber solution was quite sticky on my fingers which is something that's never happened before as it's not a glue, just a vulcanising solution so I wondered if maybe it had "gone off" or something. I've had it a couple of years but I couldn't see any use by date on the tube anywhere.

Released pressure again and it looked ok but when peeling off the clear plastic top layer it still had a few areas creeping up. So once again I slid some more gunk underneath and held it a little longer.

At this point it looked a right dog's dinner but seemed to be holding so I gave it a test pump and immediately saw that the tube bowed inwards where the patch was, as if the patch was refusing to stretch, causing that area of the tube to be thinner... Almost like it was too tight.

So I took a picture, here:
http://img23.imageshack.us/img23/8325/img974301.jpg

I decided to give up and put another spare tube in my kit for tomorrow's commute as I didn't want to risk this one.

Now if you've read this far you're a gentleman and a scholar and I thank you for taking the time. I have a few questions but please feel free to make any comments you like, although I'm not really looking for people to recommend slime tubes or anything like that, I'd prefer to concentrate on what I've done wrong here.

1) Could it be related to the fact that this tube is Schwalbe and all the others I've patched have been Specialized?

2) Has my rubber cement gone off? Can that even happen? Why was it sticky to the touch tonight when it hasn't been before?

3) Is the bowing in the picture due to using a larger patch? Does that always happen with large patches even when applied perfectly?

4) Anything else? I'm at a complete loss.

Thanks for reading.

Posts

  • term1teterm1te Posts: 1,460
    I'm not sure exactly how inner tubes are made, but it could be that too much mould releasant was left on the tube? I've seen a silicon based releasant sprayed onto complex moulds to make it easier to get the formed material out. Maybe the glue doesn't like the silicon oil? Just a thought.
  • JohnnyAllezJohnnyAllez Posts: 785
    I would have just replaced the tube and got on with life, a whole lot quicker than typing that lot :wink:
    Jens says "Shut up legs !! "

    Specialized S-Works SaxoBank SL4 Tarmac Di2
  • JameyJamey Posts: 2,152
    I don't really want to turn this thread into BikeRadar's 57th debate about whether to repair or replace tubes because we've all been there and done that before.
  • balthazarbalthazar Posts: 1,567
    Any mould-release agent was undoubtedly removed with the sanding. Vulcanising solution really needs to be left until dry before sticking the patch on, and it should be a very thin layer. I think you just got a bit frustrated, used too much solution, and –as you wrote– tried to use it a glue, "jamming it under the peeling bits".

    A repaired tube will always distort like that when inflated outside of the tyre, due to the extra thickness at the patch. Leave the tube until the next day to inflate it: you may have noticed that a freshly applied patch will still peel off – a day-old one won't.
  • The glue is a type of contact adhesive. You should allow it to become touch dry before applying the patch.
    You don't need glue on the patch and in fact you have probably caused the feathered edges to curl up by doing it.
    I always try to sand off the joint flashing on the tube to give a good flat surface to stick the patch to.
    Leave the foil backing on the patch till the last moment to avoid contamination and poor adhesion.
    Large patches will always cause a necking in a blown up tube, this is rarely a problem as the tube is restricted inside the tyre and will usually fill the space.

    Hope that this helps

    Reuse and recycle
  • JameyJamey Posts: 2,152
  • skinsonskinson Posts: 362
    Blimey!! All this work for a £3.00 inner tube. You must have a lot of time on your hands or be very short of cash. I'll see if we can have a whip round for you.
    Dave :roll: :roll: :roll: :roll:
  • JameyJamey Posts: 2,152
    See fourth post down.
  • balthazarbalthazar Posts: 1,567
    skinson wrote:
    Blimey!! All this work for a £3.00 inner tube. You must have a lot of time on your hands or be very short of cash. I'll see if we can have a whip round for you.
    Dave
    Did you never try to understand something thoroughly, simply for the knowledge? Must everything be framed in terms of cost/benefit?
  • JameyJamey Posts: 2,152
    Don't indulge him, there are hundreds of other threads online where people can argue about whether to repair or replace. I don't want this to be one of them.

    Thanks for your input so far, you've been one of the good ones.
  • redddraggonredddraggon Posts: 10,862
    Repair or replace?

    Neither. You should use tubs :wink:

    /joke
    I like bikes...

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  • balthazarbalthazar Posts: 1,567
    Jamey wrote:
    Don't indulge him, there are hundreds of other threads online where people can argue about whether to repair or replace. I don't want this to be one of them.

    Thanks for your input so far, you've been one of the good ones.

    Fair enough, but my response was tangential to that (dull) dispute. I'm astonished at the absolute absence of curiosity in some people; as if the pursuit of knowledge is a worthless occupation. Your query was clearly not about saving the cost of a tube, but about understanding the failure characteristics of the patch.
  • JameyJamey Posts: 2,152
    Absolutely, and I feel the same way as you. I always want to understand things, even if I'll never need that knowledge ever again.

    But some people don't and that's fair enough too... Don't know why they bother coming into threads like this in the first place but it will always happen.

    Have you read Zen and the Art of Motorcycle Maintenance? Sounds like you'd enjoy it, I think.
  • redddraggonredddraggon Posts: 10,862
    Jamey wrote:
    Have you read Zen and the Art of Motorcycle Maintenance? Sounds like you'd enjoy it, I think.

    I've read "Zinn and the art of road bike maintenance", storyline wasn't very good though.
    I like bikes...

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  • balthazarbalthazar Posts: 1,567
    Jamey wrote:
    Have you read Zen and the Art of Motorcycle Maintenance? Sounds like you'd enjoy it, I think.
    Yes, a long time ago... I must read it again though. I'm reminded of it often, however, particularly the BMW handlebar shim incident – which is testament to the books prescience and durability.
  • keef66keef66 Posts: 13,286
    I too am cursed by the need to understand how things work, or more commonly why they don't.
    Last night I spent 2 hours faffing about with my son's laptop. He was getting an on-screen keyboard appearing on the welcome screen. He said it didn't bother him, but I just had to fix it. I was initially convinced it had to be something to do with the accessibility options, but nothing doing there. (at one point I had added a second on-screen keyboard)
    Wasted an hour installing Vista Service Pack 2 which he'd been ignoring since September, but that made no difference. Then 5 minutes Googling led me to conclude that it was related to the Graphics tablet he'd had at Christmas. Just needed to remove a couple of un-needed windows components, and Robert's your relative!

    I mend my innertubes too.

    Can anyone tell me why they put that useless wax crayon in puncture repair kits? It doesn't work on innertubes. I use a biro.
  • skinsonskinson Posts: 362
    Did you never try to understand something thoroughly, simply for the knowledge? Must everything be framed in terms of cost/benefit?
    Knowledge!! What Knowledge is needed to repair an inner tube? I have more than enough knowledge to see me through. As I said in my previous post, you must have time to waste if you can phaff about with a £3.00 inner tube. You need to get out more! what next, washing and ironing you bar tape? How about re-lining the brake pads? :roll: :roll:
  • freehubfreehub Posts: 1,447
    Nothing wrong with repairing inner tubes, I do the same if it can save me 3 quid that could get me 2 weeks supply of flapjack, without that flapjack I'd be getting destroyed up hills.
  • crankycrankcrankycrank Posts: 1,830
    The glue is a type of contact adhesive. You should allow it to become touch dry before applying the patch.
    You don't need glue on the patch and in fact you have probably caused the feathered edges to curl up by doing it.
    I always try to sand off the joint flashing on the tube to give a good flat surface to stick the patch to.
    Leave the foil backing on the patch till the last moment to avoid contamination and poor adhesion.
    Large patches will always cause a necking in a blown up tube, this is rarely a problem as the tube is restricted inside the tyre and will usually fill the space.

    Hope that this helps

    Reuse and recycle

    Agree 100%.
  • rally200rally200 Posts: 646
    keef66 wrote:
    I

    Can anyone tell me why they put that useless wax crayon in puncture repair kits? It doesn't work on innertubes. I use a biro.

    yeah , and why that stupid cheese grater affair on the box that's too soft to powder the chalk with? -
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