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On several occasions I have gone out to the garage (at most 5-day intervals) and have noticed a flat tire on my road bike. Each time I slowly ran a trickling water hose over the fiber rim and rubber while the wheel was slowly spinning, and never noticed any bubbles. Thus, the leak must be very slow or possibly leaking out of the spoke holes.

So today, I picked up another tube (specifically, at a Trek store, 700X32 for my Domane SL7) and the rep said "there can be a dozens of ways for a tube to leak, and the issue is mostly due to quality."

Thus, is there a tube manufacturer that's known to produce more reliable tubes for road bikes? The definition of "more reliable," in this case, I believe would have to do with known manufacturers who produce tubes with greater failure/leak probability for road cycling. Obviously, a racer, mechanic, or retailer who has gone through a lot of tubes based on brand awareness could probably answer this question the best.

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  • Would be a good question for the rep
    – David D
    Apr 30, 2023 at 23:19
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    The hose test won't find a leak in a tube inside a tyre at all. You need to take the tube out, slightly inflate it, and immerse sections of tube under clear water, then look for the stream of bubbles. If its a really small hole, then it might be a very slow bubble taking many seconds to form. Have patience.
    – Criggie
    May 1, 2023 at 2:09

2 Answers 2

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To begin with, all tubes - regardless of the manufacturer or quality level - leak to a certain extent. Latex ones are notorious for losing pressure so fast that you'd want to top it up every day. However, if you are using butyl tubes you can cross at least this problem from the list. I used many butyl inners (Schwalbe, Trek, Continental, and no-names) and never had an issue with rubber quality regardless of the price point. If the tire was going flat, it was always either due to some other reason.

That being said, I'd say your water hose test is just too crude. First, check if the valve stem is screwed and seated correctly. It happened to me two or three times - a mystery leak in an otherwise sound inner tube. If this does not help, take the tube off the wheel and pump it a little, listening to any hissing sounds. Run the hands over it to feel any escaping air, as sometimes a cut can be so minuscule that no sound is made. If you can't find a leak that way, spray it with soapy water to see if there are any bubbles.

Anyway, I really disagree with your sales rep.

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  • To add to this - there are many questions and answers about checking and repairing inner tubes already, which can help you tell if yours is damaged. But even if it is indeed damaged, that damage is likely to have been caused by something else: a problem with the setup of the wheel, hitting a bump or curb too hard, rather than a manufacturing defect.
    – SamA
    Apr 30, 2023 at 23:22
  • If (when) this happens again, I'll start to monitor what's happening using the submerge method, so I can determine if there's a non-random pattern. FYI - I don't like patching something that costs <$10 each (amazon.com/dp/…)
    – wjktrs
    May 1, 2023 at 14:25
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    @user0123456789 suit yourself, but a post-mortem analysis of a leaking tube is something I always do as there might be debris embedded in the tyre itself causing the leak, regardless if I want to replace it or not. And it's still a valuable skill to have when riding long distances alone, even if you carry a spare tube.
    – Paweł
    May 1, 2023 at 15:30
  • That's a good point about something in the tire that could repeatedly cause a leak in the same area. Under my approach to start a pattern recognition method to rule out random events, I think i could find that - but I didn't have a gut feeling that something that could be stuck in the tire that could result in the same pattern - thanks!
    – wjktrs
    May 1, 2023 at 16:40
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A road bike tire outfitted with an inner tube will leak enough that it will require topping up at least weekly up to 2x/wk in my experience. Eighty to 100 psi is a lot for a tube to hang on to. If your tire is going completely flat over the duration of days or a week, this is definitely caused by a hole in the tube, a crack in the stem or the valve within the stem is either loose or damaged.

When one encounters a completely flat tire containing a butyl rubber tube (most common, non-latex) that was fully inflated days, weeks or even a month or more prior, one needs to evaluate the tube and stem for competency. This is best done outside the rim for a few reasons other than thoroughness.

I would first remove the the rim from the bike and then the tire containing the tube from the rim. Best practice would be to keep everything oriented the same so when the leak in the tube is found, you can go back and examine carefully that area of the tire and rim for possible causes. This is one reason why mechanics orient the label on the right side of the tire with the valve hole in the rim. For the odd nondirectional tire, you'll need to keep track of which is the right side when it was mounted.

With the tire off the rim, I'll strip the tube from it. The side of the tube mounted toward the right side of the bike I'll try and keep facing up or to my right. I'll put enough air in the tube to make it fairly rigid. At this point it will typically be larger than the tire that contains it. I feel it's best, especially when faced with a slow leak, to fully submerge the tire and look for air bubbles. I've used buckets or a rectangular plastic container that's 6 inches or so deep and dip one section of tube at a time. Pinhole leaks will be evident right away. I've had some that were slow enough that it took several seconds for an air bubble to form on the tube surface and then release. So be patient with each section. Note that several small air bubbles will form on the surface of the tube from the act of submersion. You can wipe these away under water.

It's almost a certainty that the leak you describe will show itself with the submersion method by a column of bubbles rising from the site. There may be more than one, so keep going until 100% of the tube is checked including the valve stem. You're most likely to have a Presta valve for a wheel fitted to a Trek Domane. After the tube is inflated prior to it's bath, screw down the valve to seal it. This way a non-sealing valve stem can be caught.

Holes that are found should be marked. I use a gold colored sharpie to circle them. You may also mark them by putting the end of a toothpick in it. Encountering two holes side by side--the so called, "snakebite," is an indication of a pinch flat. These happen when an under inflated tire encounters an obstacle and deforms enough that the tube is pinched between rim and the deformed tire. Make sure your tires are adequately inflated prior to a ride.

Note,too, where on the tube the hole was found. It's important to note whether the hole(s) are located on the inner or outer perimeter of the tube, and then go back to the corresponding area of tire or rim to look for possible causes. Check that the rim tape is covering the spoke nipples and that the end of the spokes aren't protruding through the nipples too far. On the tire side, it's rare but not unheard of to find the hole maker still in the tire. So search for any foreign objects in the tire. I use this opportunity to wipe out the inside of the tire with a damp cloth.

Finally many people like the ease and no-mess of patches that you simply peel and stick over the hole. The best fix (imo), is using the rubber vulcanizing* cement with an appropriate, sticky-backed patch. I use some sort of pressure (like a soft clamp or book) on the repair area for several minutes after to ensure a good patch that won't roll up at the edges. Otherwise follow the directions of the product.

*I'm using a loose definition of vulcanizing here, but technically correct. The rubber cement has a solvent that will soften the roughened area of the tube to be patched. This then helps the patch and tube molecules to bond as one.

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  • Concur - sticker-patches are roadside emergency fixes that tend to fail at about 10km on a road bike. They last longer on a MTB tube. A roller/brayer is quicker and better than a clamp on the new patch too. Try one!
    – Criggie
    May 1, 2023 at 2:11
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    @Criggie A "roller/brayer" as in something like you'd use on wall paper seams or drywall tape? Basically a hard cylinder of wood or plastic on an axle attached to a handle?
    – Jeff
    May 1, 2023 at 7:42
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    rubber vulcanizing cement The key word there is vulcanizing. The "rubber cement" you used in kindergarten to glue paper together is not the same thing. May 1, 2023 at 12:26
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    @Criggie interesting, I've never had this problem with a correctly applied patch. They would hold air just fine for hundreds of kilometers.
    – Paweł
    May 1, 2023 at 15:37
  • @Jeff yeah - but for patches the roller is a lot narrower. i5.walmartimages.com/asr/… for an example
    – Criggie
    May 1, 2023 at 18:43

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