Puncture repair problems

jameses

I've been having a few issues with my puncture repairs recently. After repairing the hole in the tube with a proper puncture repair kit (not the self adhesive things) and checking it has sealed properly (wait a couple of hours, then inflate and submerge in water to ensure no slow leaks), I've installed and inflated the tyre and tube.

On a couple of occasions recently, after holding pressure for a couple of days - including a couple of rides - the repair has then failed mid ride with no obvious cause :evil: . I've not hit a pothole or caught anything sharp at the time, it's just suddenly deflated. Any idea why this might be? Any way to prevent this from happening? I thought maybe over inflating to start with (up to 140psi or so, instead of the normal 90 I ride at) might simulate the extra pressure of a rider on the bike and give me an idea if it will fail or not.

Any help gratefully received

drlodge

How has the repair failed - through/underneath the side of the patch or actually through the patch itself?

fenix

Yeah work out what caused the second flat.

Whole new hole ? Or the patch failed ?

If its the patch I'd think you just need a different puncture repair set - a duff batch maybe ?

photonic69

Are you sure you have removed the object from the tyre that caused the puncture in the first place? Usually a very small shard of glass (IME) and hard to see. Perhaps its repuncturing?

jermas

Maybe the adhesive/patch is old and past its best? Not waiting for the cement to dry long enough (~10mins) before applying the patch can cause problems, especially in damp weather. Also over-inflating the inner tube whilst not inside the tyre could overstretch the repair patch.

jameses

How has the repair failed - through/underneath the side of the patch or actually through the patch itself?

underneath the side of the patch

Yeah work out what caused the second flat.

Whole new hole ? Or the patch failed ?

If its the patch I'd think you just need a different puncture repair set - a duff batch maybe ?

Patch fail, definitely. I always check for debris in the tyre, even put a little air in the punctured tube to see where the air was escaping from. Duff batch of patches is possible, I guess, but some have held and a couple haven't. I suspect it's something to do with my repairing, but I don't get why it can be fine for a few days (including rides) and then go with no obvious cause

Maybe the adhesive/patch is old and past its best? Are you leaving the adhesive long enough before applying the patch? Not waiting for the cement to dry (~10 mins) can cause problems. Also over-inflating the inner tube whilst not inside the tyre could overstretch the repair patch.

New set of patches; adhesive was left to dry. Maybe over-inflating the tube outside of a tyre is a cause - I usually put 7-8 strokes of a track pump in to see if it's holding.

jermas

Are you sandpapering the inner tube to give a key?

mamba80

You dont need to inflate the tube and submerge in water after the patch has cured on the tube, the patch is no where as flexible as the tube and its probably just pulling the patch off.

The Rookie

Sand tube for grip before gluing.

Adhesive on tube and leave for 5 minutes for it to go 'gooey'.

Peal off protective coating from patch and stick over.

Apply a heavy weight while it sets, I use some books and cover the patch with a cheap (filmy style) carrier bag as they don't stick to the adhesive and peel off.

If your tubes are on the small side it can cause issues as the tube stretches more than the patch.

I use Weldtite patch material as you can cut it to size so I have tiny patches, usually about 6-8mm diameter.

CiB

To add to Rookie's guide above, I always put the patch on with enough air in the tube that it's roughly the size that it'll be inside the tyre, that way the patch isn't being stretched when you do fit & inflate it. I'd also drop the 7-8 strokes to inflate it and test it before fitting; if you've fitted the patch properly it'll hold. There's no need to test a known process that's worked for the best part of 100 years. And vulcanisation is usually adequate within a couple of minutes so it's ok to fit the tube then, instead of leaving it a couple of hours. Never needed to put heavy weights or books on a tube either, just a firm pressing action between thumb & forefinger to attach the patch evenly all over. One last thought - avoid all contact with both contact surfaces, the thin smear of glue needs to be tacky enough but not dry, and the patch must be completely free of any contaminants from your fingers. And use the smallest patches possible, the ones smaller than the size of a 1p piece are best.

keef66

That's a lot of pumping, especially with a track pump, for a recently repaired tube, so I'd say that's what's causing the failures.

I just have faith in my repair technique, and fully inflate it but only once it's inside the tyre. That way the bond isn't being stretched by the differential expansion of patch and tube, and it's being pressed firmly against the inside of the tyre

fenix

JamesEs wrote:

. Maybe over-inflating the tube outside of a tyre is a cause - I usually put 7-8 strokes of a track pump in to see if it's holding.

Yeah I think thats probably weakening the patch. Doing that in the tyre is fine as it compresses against the tyre. Here you're just begging the air to push through the hole and bubble under the patch.

jameses

Thanks for all the replies, sounds like the 'test inflation' is what's causing the problems. I'll have another go at it later.

Moonbiker

Rema Top tip seem better quality than other patches imo.