22

When I have a flat tire, I find punctures in inner tubes using three techniques, all starting with the inner tube outside the bike:

  1. Hearing where the sound of air escaping originates.

  2. Feeling the escaping air with my hand.

  3. Putting it inside a container of water and seeing the bubbles. I end up using about 10 liters of water, and I have to rotate the inner tube to pass all of it through the water.

Is the method 3 smart? Could water get inside and damage the valve? All three methods seem to work very fast. Is this just a matter of taste or does some miss some punctures?

  • 7
    Whatever works. – Daniel R Hicks Dec 21 '16 at 22:50
  • 1
    @StephenTouset You avoid repairing always that you can but new inner tube? – Santropedro Dec 22 '16 at 0:10
  • 7
    @StephenTouset to patch or replace is a whole separate question. This is asking about locating the holes in the tube. – Criggie Dec 22 '16 at 0:32
  • 7
    @StephenTouset : Tubes may be cheap, but rarely are recycled. Save the planet one puncture at a time - apply a patch. – mattnz Dec 22 '16 at 0:40
  • 1
    @NateWengert - why would you use windex? Even if its safe for the rubber (is it?), it seems like an odd thing to reach for. – Batman Dec 22 '16 at 0:42

11 Answers 11

22

Do whatever works, really.

The problem with the container of water approach is that it requires a container of water. It won't damage the tube. Also, if you need to patch the tube, you have to wait for the wet tube to dry. So, I'd generally recommend doing this last (usually leaks are not subtle enough to need the immersion), but no harm going there first.

The usual technique I use is to try to blow up the tube a bit and put the tube near my upper lip if I can't find the leak by ear or feel it around the tube with my hands; the upper lip area is pretty sensitive, so its pretty easy to detect it. Try to be systematic about it, like start with the valve and go clockwise. If you jump around all willy nilly, you'll take longer to find it.

Sometimes you get leaks that are too slow for that, and generally in those cases, you end up replacing the tube anyway.

You can also trace the leak by checking near the valve (a common culprit; if its the valve itself in a Schrader valve, you can spit on it and check for bubbles) as well as running your hand along the tire to see if anything is there. If you make sure to align the label of the tire (e.g. where it says "Continental" or whatever) over the valve, its easy to work back to where the leak is if you find something (since the label and valve are in the same position, the position of what you found relative to the label tells you where the leak is on the tube).

See this page as well. It also covers what leaks mean stuff (if you have a thorn in the tire, chances are that's your cause, for example. Snakebites are often insufficient tire pressure. If you have a leak on the rim side of the tube, chances are theres something off with your rim tape, etc.).

  • Wow, I never thought the valve could leak! One thing more to check. – Santropedro Dec 21 '16 at 22:53
  • I don't understand this paragraph the (last-1) paragraph: "You can also trace the leak..." for some reason this paragraph is confusing. Questions: Why near the valve? Why in first pllace i wouldn't be looking there, if I'm looking everywhere? Spitting inside the valve to see if trows bubbles? Why aligning something tells you were the leak is? – Santropedro Dec 21 '16 at 22:56
  • @Santropedro - I've edited it, hopefully its a bit clearer. Tubes often take damage near the valve, such as from attaching and detaching your pump, especially at an angle. – Batman Dec 21 '16 at 22:59
  • 1
    The first time I read I did not notice the word "tire" at all in your post, even if it was there, because unconscious blindness/bias). In fact, I realized now you are suggesting a 4th technique to find punctures, that is, looking for the "cause" in the tire. – Santropedro Dec 22 '16 at 0:13
  • 3
    @Santropedro: looking for the cause is usually not in order to find where the puncture is but so you can remove the cause to stop it happening again: if a shard of glass is sticking out of your tyre you need to remove it before putting the inner tube back in! – PJTraill Dec 22 '16 at 1:34
17

To follow up on what Batman says, what you use to find the leak depends a lot on the circumstances.

If you get a flat by the side of the road (and you don't have a spare tube) then you obviously can't use the tub of water (unless you find a convenient pothole filled with rainwater). In other circumstances the water tub (or bathroom sink or whatever) is reasonably practical, but it may not be necessary.

First consider the circumstance. You're riding along and suddenly hear "Pfft, hiss, hiss, hiss..." as the tire rapidly goes flat. You can't ride home on the rim, and your spouse can't come and get you, so you need to fix the flat.

Even if you have a spare tube you should find the leak and check the tire at that spot for something embedded (or else your spare tube may be holed as soon as you inflate it). So you remove the tube, keep track of which side is which (if possible) and find the hole. Usually the way to do this is to inflate the tube with your pump and loop it over your head, as you rotate it around, listening for the leak. When you hear it, hold the suspect portion of the tube near your face to feel the wind blowing on it, to zero in on the hole.

Having found the hole (if possible, marking it with pen or chalk), you then lay the tube on the tire, aligning the valve stem with the valve hole in the rim (here is where it's nice to know which side is up, so you don't have to check both ways), and then check the tire in the vicinity of the hole for any embedded wire, nail, glass, or thorn.

Sometimes, though, a leak is hard to find by hearing/feeling it, either when it's too slow, or when it's so fast that the tire won't hold air long enough to listen/feel for it. In these cases a water tub is the way to go. The water tub is also handy for discovering valve leaks.

  • 1
    "You're riding along and suddenly hear" If only it was that easy, I almost never hear my tires leaking, either it's too subtle or the environment is too noisy. But yea, you pick whatever you got handy at the moment. Regardless of planning, there's no method that will work 100% of the time. Get creative. – Mast Dec 23 '16 at 11:48
  • 2
    @Mast - My point was that the tire goes flat so rapidly you don't have the option to dash for home. With slow leaks you can keep pumping up and go for several hours if need be. – Daniel R Hicks Dec 23 '16 at 13:19
8

Not mentioned, but a technique that works best for me is to use my lips.

I've been an avid rider for 20+ years and have tried most everything to find those pesky little leaks. Water is good, but not always convenient. However, I always have my lips with me -- and I've found them to be sensitive enough to find even the smallest of leaks.

The technique is easy, just blow up the tube, place it around you head and rotate it ensuring that every part of the tube passes by your ever so slightly opened puckers. It there is a leak to be found, you will most likely find it that way.

  • Licking your lips first helps. Don't forget a puncture is most likely to be on the outside of the tube (I don't put it round my neck when I do this, if you do you need to make sure you're testing the outside) – Chris H Dec 22 '16 at 8:04
  • @stevej How many "turns" do you need around the torus? One for the inside and one for the outside? – Santropedro Dec 22 '16 at 12:42
  • @Santropedro; It usually doesn't more than a couple turns, but @Chris H is correct - you have to get the hole tube (inside, outside and sides). If the hole is really, really, small and I'm really desperate, I'll resort to using my tongue. It is more sensitive yet and has never failed me -- but you inadvertently will end up licking the tube. – SteveJ Dec 22 '16 at 14:40
  • I've used my nose too :p – Paul H Dec 22 '16 at 18:29
  • @PaulH Good one, I can see that working equally well as our noses are also very sensitive. I'll give that a try next time. I think many parts of the face probably work - cheeks as well. – SteveJ Dec 22 '16 at 19:11
7

If you do use a bucket of water, one thing that I was taught was to put a teaspoon of dish detergent (the foaming kind) in the water.

1) If the water you use is on the shallow side, the foaming or bubbles will help you locate the pin prick a bit better. This is especially important for slow leaks, such as valve leaks.

2) The soapy water will also help clean the area around the leak, so patches will adhere just a bit better.

4

Mostly to reply to your second question: I've had punctures/valve problems so small that when the tire is held under water it would take at least 10 seconds to form one bubble of air coming out. I could not feel this 'breeze' with my hands or lips. So I consider method 3 the most failproof as I don't know any other ways one would be able to find such a small leak. For the rest everything has been said by the other answers: if you hear the hissing there's no real need for any other method, on the road you might not have access to water or it's just inconvenient to patch so you're better of taking a spare tube and patch the punctured one at home.

  • 1
    Depending on your risk acceptance and your space, I take one spare tube always, plus one more per 50 km. So a 120 km ride I'll carry three pre-tested tubes to use or give away. – Criggie Dec 22 '16 at 21:42
2

To prevent additional accidental puncturing the inner tube while moving it around to dip into water, I usually use my wet fingers to touch the inflated tube. It requires less water and leave the tube less wet for the repair action.

Regarding your concern that water may enter the tube, the air is going out because it is at higher pressure than the water, not because it is removed by buoyancy forces (like when you push an open and empty bottle under water). Therefore no water can enter trough the puncture

  • How could you accidentally puncture the tube while immersing it in water??? – Daniel R Hicks Dec 22 '16 at 12:54
  • not the part immersed in water. The tube can get squeezed between the brakes and the rim or between the fork and the spokes, and if one doesn't pay attention here it is an additional puncture. (assuming one simply extract the tube from the tire without separating the tire from the bike) – L.Dutch - Reinstate Monica Dec 22 '16 at 13:00
  • And even if a whole droplet of water did go into the tube, its will evaporate inside the tube and slightly increase the humidity. This is no worse than pumping atmospheric air into the tube on a damp day, or having a drop of water in a schrader valve then pumping. Additional humidity will increase the "rubber tyre" smell when you deflate it next time, that's all. – Criggie Dec 22 '16 at 21:46
2

I usually can't detect my punctures except using water. When I use water I discover that the puncture is tiny.

The bad thing about water is that you can't easily use that method in the field or on the road; and the good thing about tiny punctures is that you can wait until you get home.

Symptoms of a tiny puncture are:

  1. Bike is fine when I put it away at night
  2. Tire is flat when I get it out the next day

Or:

  1. Discover that tire is flat when I'm riding
  2. Reinflate the tire without fixing it, and steer towards home
  3. Tire remains inflated for at least 20 minutes before it needs reinflating

Tiny punctures come from a tiny object embedded in the tire.


If (only if) it were a bigger puncture, then I guess I couldn't reinflate without fixing it, but also wouldn't need water to find the puncture.

  • 1
    Agreed - a tub of water is perfect for use at home. which is why you carry spares. – Criggie Dec 22 '16 at 21:43
2

I find the most efficient way to find leaks in both tubed and tubeless tires (automobile) is to fill the tire with the recommended air pressure + 5 lbs for tubeless tires,(For an inner tube I fill it to 2 times its normal size, In other words, if you have a tube that is 2" wide when pressed flat, fill the tube until the tube is roughly 3" in diameter. If the tube is partially aired up, then just double its circumference. Don't worry too much about it popping. If you have ever seen one of these things filled to the point of catastrophic failure you would understand that most tubes will expand up to 4 sometimes six times the normal circumference. So keeping it at around double its operating size will ensure you won't pop your tube.

Before I air up the tire or tube, I locate an empty refillable spray bottle and add about a teaspoon of dishwashing liquid, then slowly fill the bottle with water so you don't fill the bottle with bubbles. I like to use the spray bottles that have a straight stream. The mist type creates fine bubbles that can work if the leak is big enough, but if it's a small leak, then it's like trying to find a needle in a haystack or in this case a bubble in a bubble bath. Also find a light colored crayon or wax pencil or even liquid paper so you can mark the location of your leak once you find it.

I normally run the back of my hand and fingers (the back of your hand and fingers are covered in small hairs that make it more sensitive to wind or air moving across them) around the outer ring or the part of the tube that faces the ground when you roll it. This is where most punctures occur from normal everyday riding. That changes if you are mountain biking or just off road for even a little bit. If so, you'll need to expand your search up the sides of the tube to be certain your leak is not there. Next, I check the inner ring (the side that faces the rim) If you find a leak here it is going to be either an equipment error or operator's error. The spokes of the rim should not be exposed to the surface of the tube. I know on older bikes there was a rubber belt/band that acted as a buffer between the rim and the tire, covering the spoke heads. Make sure there are no jagged surfaces on the wheel and spoke heads before reassembling your tire and wheel. //////CAUTION!\\ Before you go swooping your hand around that rim remember that what you are looking for is sharp enough to either have punctured or worn a hole in your inner tube, so be slow and use a light touch so you won't lacerate your hand or fingers. Do the same thing with your tire while you have the tube out of it (Again with CAUTION) to be sure you have removed any foreign debris or protrusions that have impaled the tire and was the cause of your flat or could be the cause of your next flat. After streaming the soapy water mixture onto the tire about a 6" section, pause for two to three seconds and if no bubbles have formed move to your next 6" section. Continue until you find the leak and when you do find it, grab your lite colored crayon, wax pencil or liquid paper and circle or "X" the spot where your leak is. Believe me, if you take your eye off of it, then look back at it, more often than not you won't be able to locate it without spraying it again.

I suppose you already know how to patch a tire so I won't walk down that road unless you need me to. To answer your question about the valve being damaged. Yes, water can damage the valve by oxidation. Just a small particulate of rust can cut or tear the rubber seal on the valve core. After spraying it to check for leaks and before I fill with air again, I use compressed air or even use the bike air pump to blow out the valve stem to clear it of water and debris. So I would say the way you've been doing it is good. The other answers offer some good tips also. It's one of those things that if you do it right, there are probably several ways to get the same result.
Happy Riding.

  • 3
    All good advice, but what does the image have to do with finding the hole in the tube ? Remember SE is all about the question and its answers, so try and avoid getting side-tracked. We don't do signatures or tags or anything in answers. The rest of your answer is great though. – Criggie Dec 22 '16 at 9:49
  • You can't fill a punctured tyre to it's recommended pressure, even with a compressor and a tiny slow puncture this is unlikely to work – Vorsprung Dec 24 '16 at 8:26
  • @Vorsprung First, for tubeless tires: my customer has spent his tire budget for the next two years So I now tend the slow leak. I inflate to 170psi he comes back120-140psi. So punctured tires can be inflated. You can't inflate tires with a hole that the air just rushes out as fast as you put it in. Question asked: how best to find a leak. if leak is huge won't be trouble finding the hole. need a new tire, not a flat repair. – DJ Qu8ke Apr 13 '17 at 17:41
1

Finding leaking compressed air or gas from a tube or container is as much luck as having a sharp eye. The best technique I have found is to use simple dishwashing liquid (do not thin it out too much) and put a little over the areas in question. Luke submersion in water bubbles will form, but unlike underwater the bubbles stay (you have to wipe them away but you can get down to the actual hole (or holes) The added bonus is you were going to have to clean the area before applying any adhesive so once found and marked you only need to rinse the soap off and allow to dry.

1

The easiest method that always works for me is to over-inflate as @DJ Qu8ke mentioned, but then simply move my fingers and palm along the tube slowly but lightly, trying to 'touch' the leak. There must be some air escaping somewhere, or you wouldn't have experienced a flat or soft tire.

When you touch a leak, you can't actually seal it by resting a finger over it, but you do increase the speed of the escaping air, however weak it might be. What happens is that the pressure of the air in the tube has a constant positive pressure. So even if the leak is tiny, pressing on it with your skin causes resistance and deflects whatever stream of air is escaping.

The deflected air stream will hiss (which makes it a primitive musical instrument for those who are easily amused) even if it is faint. If it is a strong leak you can actually make it whistle. But those aren't the leaks that are hard to find.

Once you hear even a faint noise, you can 'echo-locate' the general area and search more carefully. Eventually you will find the location where lifting and replacing a finger over the leak will produce intermittent interruptions in the hiss and you'll know you have found the source.

However, when the leak is faint, you probably have discovered a weak area of the tubing, and so you should expect to find several of these leakettes. So cover each of them with a finger until you are able to decide that you can cover the entire area with a big patch, or that you will have to walk home with the bike on your shoulder.

Easy, and no artificial ingredients required!

  • 1
    It should be pointed out that "over-inflate" does not mean inflating the tube to 80psi, if it comes from a 60psi tire, but means inflating the tube until it swells up somewhat larger than it's "normal" size (maybe 50% larger). I've never measured it, but I would guess this means 5-10psi. – Daniel R Hicks Dec 24 '16 at 4:40
  • 1
    @DanielRHicks agreed - tubes outside of tyres normally stay in the area of 10 PSI, they just start inflating like a balloon. – Criggie Dec 24 '16 at 8:55
  • @kimball johnson Welcome to bicycles.stackexchange! You say "When you touch a leak, you can't actually seal it by resting a finger over it"... Well I could in my experience with the leaks I've had. – Santropedro Dec 24 '16 at 13:57
1

One technique I haven't seen mentioned here is checking the outer tire. You need to do that anyway, to remove any culprit that caused to puncture and is still stuck, or you need to mend your tire twice.

First inspect the outer tire while still on the wheel. If that yields nothing, pop of one side of the tire off the rim and feel the inside carefully(!) with your fingers, taking care not to shift the tire along the rim.

If that yields nothing either, you continue using the various techniques described in other answers.

  • If you can find the leak in this way you may be able to avoid taking the wheel off. If it's something like a push pin (like on the ground under our local bulletin board), check to see if the pin has poked a hole out the other side. – Keith McClary Dec 25 '16 at 21:03
  • 1
    Common practice is to line the tyre's label up with the valve stem so you can associate the hole with an area of the tube (or the other way, show you what area of the tyre needs checking once you find the hole in the tube.) Even if you flip the tube by mistake, there are still only two areas that it could be. – Criggie Dec 25 '16 at 21:07

protected by freiheit Dec 28 '16 at 20:26

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.