21

Any thoughts - my spare tube that I carry in my bag currently has a dozen or so patches on it, but still works fine. I'm tempted to keep going to see how many I can get on there until it get impossible to mend.

What is the most number of patches you reckon a tube can take ?

(And I know new inner tubes are only £5 or so, but a puncture repair costs about 10p if you buy the patches and glue in bulk, so "It's cheaper to buy a new one" is not necessarily true...)

1
  • Comments have been moved to chat; please do not continue the discussion here. Before posting a comment below this one, please review the purposes of comments. Comments that do not request clarification or suggest improvements usually belong as an answer, on Bicycles Meta, or in Bicycles Chat. Comments continuing discussion may be removed.
    – Criggie
    Commented Feb 5, 2023 at 17:58

5 Answers 5

18

When the patches start to overlap, or you are fixing old patches that have failed, it is time to get a new tube.

3
  • I know it's been a long time since you wrote this, and you got a lot of upvotes without anyone questioning anything. But do you really mean that the tube should be replaced if it's the patch(es) that failed? In my experience patches fail sooner or later because I applied them improperly, and not through the tube's fault.
    – pateksan
    Commented Feb 8, 2023 at 18:19
  • @pateksan If one patch fails its likely another will fail soon after refitting the wheel.
    – Ian
    Commented Feb 8, 2023 at 22:42
  • I strongly disagree. A patch can fail for several reasons. Three which seem notable are the skill/performance of the patching operation and the quality of either the vulcanising fluid or the patch itself. I think there are a lot random factors involved in all three. And hopefully we can agree in that much that the level of randomness would require a separate discussion.
    – pateksan
    Commented Feb 9, 2023 at 19:14
18

I would carry at least one unpatched, pristine tube as a spare. Put the patched ones on the bike or keep for repairs at home. The idea being that when you need it -- in the middle of nowhere, in the dark and pouring rain -- you're guaranteed that the old patches aren't peeling off or weakened and the tube should "just work". Then swap it for a patched tube when you get home if you like.

1
  • 8
    If they are rolled or folded as a carry on spare the patches are more likely to peel off on the wheel. Commented Sep 9, 2010 at 8:54
13

I find the bigger problem is not the number of patches, but rather the age of the patches. There is a correlation though, in that by the time you have patched a tube for the third time, I find that the first patch is starting to get a little suspect.
In my student days I would patch a tube four or five times, but I often had patches eventually fail.
Nowadays I draw the line at two. Tubes are just too cheap to have one fail on you in the middle of a ride. The time and inconvenience of having to change a tube that has failed is not worth the money, especially since it always seems to happen on wet windy nights!

4

I strongly contend the rules of thumb about the number of patches. I have used (and I am using) tubes in 2 different mountain bikes, with 8-10 patches, and they perform exactly as new ones. They get punctured by evident spikes, nails, etc., the same as brand new ones would suffer.

As for the age of patches, it is but a mild indicator, at best. Again, some of those patches are certainly older than 10 years (and I would dare saying some are older than 25 years), and they don't leak, as they were properly applied. I can't remember seeing a patch failing in my tubes.

The gross points to be careful about (as others mentioned) are:

  1. Don't patch close to the valve.
  2. Don't patch too close to the edge of another patch. If you want to be cautious, avoid even minor overlaps.

Other than that, I conjecture there must be some incidence of other factors on the life of a tube (although I cannot attest for any evidence from my personal experience or any friends'):

  1. Quality of the glue or patches.
  2. Improper patching process (tube not completely deflated, improper glue drying, etc.)
  3. Storage conditions (for spare or installed tubes).

I think any suggestion should be based on factual information.

2
  • 1b - size of the patches. I have some rather cheap ones that are a bit big (also a bit stiff) for touring tubes. They work perfectly on mtb tubes but have been known to fail the initial test on narrower rubber. If they pass that test, they're good.
    – Chris H
    Commented Jan 31, 2023 at 7:07
  • This is impressive. I was convinced that 25 year old tube would leak when installed even if it previously has never seen a wheel for all this time.
    – nightrider
    Commented Feb 1, 2023 at 15:58
3

Answer: As many as it takes till you can't patch it the last time.

I have one 26" MTB tube that has fifteen patches on it. Some of them might be two small round patches on a pinch flat, but it holds air perfectly well.

I'll replace it when I can't get a puncture to patch properly.

On the other hand I've had road tubes that won't take a patch for some reason - the butynol rubber just "rejects" the vulcanising fluid and after some minutes of test at pressures below 5 PSI it just lets go. Those get the valve cut out for bottle rockets, and are put on the "emergency tie downs" hook.

Of course I ride with a spare tube for each wheel size on the bike, and I carry sticker-patches as a last resort or to help other people. If its a long ride I'll sling a second or even third tube in. So even though a patched tube goes back into the rotation, its not the only thing I'm depending on.


My normal patches are "cure-c-cure" and weigh 9.3 grams for all 15 or 0.62g each. For comparison,

  • 15 small budget orange-edged patches weighed 9.7 g or 0.65g each
  • 8 medium budget patches were 7.7g or 0.96g each
  • 4 other medium orange-edge patches were 3.1g or 0.78g each
  • 1 large budget patch was 1.9g

Assume the weight of cured vulcanising fluid roughly equals the weight of the backing foil:

A 26" / 559 tyre with a rolling circumference of around 1.75 metres needs 87 patches of 20mm diameter to completely surround the outer edge.
87 patches at 0.65 grams is 56.5 grams. Which is not insubstantial but represents 1/11th of a full drink bottle or one large gel.

Those patches would cost you around $20, two tubes of gloop another $20 for a total of $40. Compare that to 87 new budget tubes at $5/each is $435 total.

Upshot "patch till you can't patch no-more" unless you're competing in a race where every gram counts.

5
  • 1
    How does the weight of your 15 patch tube compare to a new tube? (same model) Would also be interesting if and how it affects rolling resistance.
    – Michael
    Commented Jan 31, 2023 at 10:01
  • @Michael no idea - I think its on the bike right now. I'll weigh 15 patches tomorrow and update
    – Criggie
    Commented Jan 31, 2023 at 12:19
  • 1
    @Michael On the plus side, you can think of it as extra puncture resistance!
    – MaplePanda
    Commented Jan 31, 2023 at 13:47
  • Sorry - keep forgetting to do the weighing.... its on the todo list, honest !
    – Criggie
    Commented Feb 2, 2023 at 9:36
  • @Michael Done - short answer is "about a gram per patch" details in answer now.
    – Criggie
    Commented Feb 4, 2023 at 4:31

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