Patches where the cellophane adheres to the patch after a tube repair.

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smutchin

Cat 6 Racer
Location
The Red Enclave
If you leave the cellophane on, what happens when the tube stretches to fit the tyre?

The patch is stretchy, the cellophane isn’t, so I’ll give you two guesses.

I leave patches to cure before re-using the tube, by which time the cellophane often comes off more easily. And if it doesn’t, I just leave it on. As @User9609 says, it helps stop the tube sticking to the inside of the tyre.
 

Fenrider

Is't far you ride?
The patches I used to use you had to fold the patch sharply thus stretching the covering which then cracked. This made it possible to peel off from the centre. But they weren't cellophane but more like tracing paper.

I find this technique still works with modern patches. With the cellophane backing still attached, firmly press the patch onto the tube, then make a fold across the middle of the patch which will cause the cellophane to crack. You can then peel the cellophane off the patch from the centre to the outer edges without lifting the feathered edge of the patch.
 

slowmotion

Quite dreadful
Location
lost somewhere
I loathe fixing patches at the roadside and I will do anything to get away, not least to stop the flow of blood from under my fingernails. At home, the cellophane stuff is an annoying challenge that I relish.
 

Globalti

Legendary Member
That's not good. The patch is supposed to stretch and conform to the tyre. If you prevent it from doing this you are introducing a potential weak spot and sudden failure of you and the bike to proceed in a forwards direction.

An experienced tyre-fitter would not trust the cellophane to prevent the patch and surrounding glue from sticking to the tyre, they would remove it then dust the tube and tyre bead with talc, Nature's own dry lubricant.
 

TheDoctor

Europe Endless
Moderator
Location
The TerrorVortex
But the cellophane cracks all over the patch, as per the photo above.
Assuming that's a 25mm patch, some of those bits are only a couple of mm across.
 

Globalti

Legendary Member
I don't care; for me it's a weakness. A thin airtight layer of latex or butyl rubber trapped inside a strong tyre carcass is an excellent design and pretty bombproof but this compromises that perfection and if I'm blasting down a hill at 40 mph I don't want weaknesses in my tyres.
 
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Alan O

Über Member
Location
Liverpool
[QUOTE 5352118, member: 9609"]One thing I find interesting, the photo shows the scratches in the tube where I have rubbed it with sandpaper, however those scratches have all but disappeared under where the paper/foil was (the paper foil would have been an oblong shape that can just be made out)[/QUOTE]
Interesting, yes - presumably the limits of where the rubber solution reached?
 

smutchin

Cat 6 Racer
Location
The Red Enclave
The patch is supposed to stretch and conform to the tyre. If you prevent it from doing this you are introducing a potential weak spot and sudden failure of you and the bike to proceed in a forwards direction.

The cellophane does not prevent the patch stretching - it's too thin and fragile to put up any resistance to stretching forces*, and isn't stuck that firmly to the patch anyway. Leaving the cellophane on the patch does not cause a weakness in the repair.

*this is proved by the fact that as someone noted earlier, if you fold the patch after applying it to the tube, the cellophane simply cracks.
 
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