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Normally, when applying a patch to a tube, both the patch and the tube surfaces are smooth and it is easy to press the patch onto the tube.

However, some tubes have small ribbed areas where it is hard to get a patch to fully adhere.

What do you do to avoid small air leaks by a rib?

Photograph: Photograph of a small air leak in the ribbed area of a tube's patch

Recently, I had another leak in the ribbed area so I took the advice and used a smaller patch, scratched things up better, waited 5-10 minutes, and pressed down with my full body weight. The patch lasted about a week before developing the following slow leak.

enter image description here

Zian Choy
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    Frankly, unless I really need to get that tube patched I toss it and use a new one. If you do attempt to patch it, you need to clamp it hard for an hour or two, using, eg, a couple of 2" squares of plywood and a C-clamp. – Daniel R Hicks Sep 17 '17 at 00:58
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    On a sidenote: At least ParkTool advises against removing the clear plastic cover from the patch. – Michael Sep 17 '17 at 08:45
  • @DanielRHicks do you have any source for the requirement of 2 hours of clamping? For what brand of vulcanizing agent? I've patched more tyres than I can count including plenty of successfull patches on ribbed areas and never used more than a minute of firmly pressing by hand. Which leads me to believe initial clamp force is what matters, not duration (i.e. vulcanization taks place immediately). But I can be wrong of course. – stijn Sep 17 '17 at 18:43
  • @stijn - Just my experience. Can't say for the exact time, since I'll clamp it and then set aside and do something else. Certainly a lot depends on the quality of the patch, and, possibly, the quality of the tube. – Daniel R Hicks Sep 17 '17 at 18:58
  • @DanielRHicks Interesting - I give a patch 10-15 seconds of high-hand pressure rolling using my special roller tool, and that's about it. – Criggie Sep 18 '17 at 04:56
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    @Criggie - It may have to do with the age of the tube. Most tubes I work with lately are 10-20 years old. – Daniel R Hicks Sep 18 '17 at 12:06
  • Unless you are really short on money: Just buy a new tube and proper puncture resistant tyres! See it as an investment: You pay a bit more now, but you get immense returns on it in terms of reliability and of time not lost due to suddenly being stranded with flats and having to patch tubes. If you can afford that investment, it's more than worth it. – cmaster - reinstate monica Feb 28 '18 at 14:06

1 Answers1

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More careful buffing - the ribs stop the sandpaper/scratcher from getting into the butyl rubber and exposing raw rubber, so the vulcanising agent can't work so good.

You don't need to buff the ribs off completely, but scratching up beside the ribs helps a lot.

Also, over-size the area that you cover when you spread agent. Those orange edges should be stuck down firmly.

Another help is to use a larger patch in these areas, but it means more buffing because more surface area. You can also rotate your patch 90 degrees to cover the length of the ribs more.

Also make sure to wait 5-10 minutes after applying vulcanising agent, before pressing the patch on. Then press patch firmly. I use a roller the width of two coins, but a large round coin works fine too.

Criggie
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  • With traditional patches this approach has always worked for me (though I use a clamp because I patch at home if at all possible). With glueless patches it will be a lot harder – Chris H Sep 17 '17 at 06:29
  • @Criggie From the scale of the blurry bits of finger/thumb in the picture, I am guessing it is a 22-25 mm tube. (unless, maybe, the questioner is holding it with their feet). So while I agree with all the rest of your comments, I believe the patch in the picture is already too big. Much easier to use one of those small round patches (the ones about 15 mm across), because it is easier to properly prepare (and apply glue to) a smaller areal of the tube. – Penguino Sep 17 '17 at 22:24