13

My rear tire gets flat almost every month without any obvious reasons. Few times it lost the pressure while riding but I do not see or remember puncturing it, and once it was on a good tarmac street where I would not expect. Yesterday I parked the bicycle in the morning after arriving and found the tire flat in the evening. For some reason it is very difficult to change the tube for this rim, so I now bring the wheel to the repair shop where they stoically do every time. I think this started to happen after the rear rim has been replaced, following the freewheel failure.

It is a 2.35 inch wide tire (that I have replaced once with no effect), 27.5 inch wheel. Both me and my E-bike are quite heavy (I do not know the exact weight of either). The road combines sections of both gravel and tarmac. About 15 km needs to be covered every day. The front wheel serves well.

When I bring my flat wheel to the repair shop next time, maybe I can ask them to do anything more with it than change the tube? Or should I ask them to order the parts of they choice and "build another like this"?

3
  • 4
    What air pressure do you put into your tyre? Does the bike shop just fit a new tube every time - do they not look for the cause ? If its in the same place every time, then the cause is stuck in your tyre.
    – Criggie
    Mar 19 at 12:15
  • 9
    I suspect that a spoke end is poking into the tire. Mar 19 at 12:57
  • 14
    @DanielRHicks Or a bad tape job on the rim leaving a spoke hole or five uncovered. Either way, if it's the same shop that replaced the rear wheel then milked how many tube replacements, it's time to find another shop and learn how to fix flats yourself. Mar 19 at 13:04

4 Answers 4

42

First, learn to change your own tubes. It's not hard, and you really should be able to do it. Because, frankly, if you're taking this same bicycle to the same shop every few weeks for them to change a tube, and they're not taking the time to really solve the problem, they're ripping you off.

Because it seems like they're not even trying to find the cause. They should remember you bringing the same bike in every few weeks. That's especially true if this is the same shop that replaced your rear wheel/rim.

Also, you need to be able to take a tire off to really solve problems like this yourself - in less time and for less money than it takes to haul your bike to the bike shop, and then go back and get it days later.

Now, for why you keep getting flats after a few weeks - something is slowly working its way through your inner tube. It could be in the tire; it could be somewhere on the rim.

First, are you inflating your tubes to a high enough pressure that they don't get pulled around the rim? If your valve stem keeps going cockeyed and gets slanted instead of staying upright where it pokes out of the rim, you're running your tubes at waaay too low of a pressure, and the tire and tube are slipping around the rim. But the valve can't move, so the tube pulls at it and is quite likely to tear and fail.

Another possible cause of flats related to using too low of a pressure is something called a "pinch flat". A "pinch flat" happens when you hit something and, because the pressure is low enough, the tire gets compressed to the point that it gets pushed hard into the rim. The tube gets flattened and pinched between the tire and the rim, literally cutting holes in the tube. The holes are usually paired because the tube when the tube gets flattened, both layers are caught between the tire and rim and two small holes get sliced into the tube. Pinch flats are often called "snake bite" flats because of the paired holes.

Pinch flats are more likely when tire pressure is too low - it's easier to compress the tire enough to pinch the tube.

IMO, you're not likely getting pinch flats - those are usually pretty clearly related to hitting something hard enough that you notice it, and then your tire(s) are immediately flat. I suspect if that were the case, it would have been noted in the question.

If you're not underinflating your tires, get the failed tube off, and find the hole. You now know just about where in the tire or rim the problem is likely to be. (This is one reason why experienced cyclists and bicycle mechanics always mount a tire with the label at the valve hole - when you get a flat, it's possible to determine where the cause is...) The hole may not be exactly where the cause is - the tube can be stretched and twisted some inside the tire, but it should be in the same general area.

Check the rim - it's easier and faster to check the rim thoroughly, and given your flats likely started after a wheel change, IMO the most likely culprit. Start in the general area where the hole is.

Look at the rim tape - the strip that covers the spoke holes in the rim. Is it evenly applied? Does it cover all the spoke holes properly? Is it bulging badly into the spoke holes? Is the rim tape torn or cracked anywhere?

That's the most likely cause, IMO. If a spoke hole isn't fully covered, the tube will bulge into that hole and the slight flexing the tube undergoes when you ride will slowly cause a hole to form.

Are there any too-long spokes protruding through the rim tape? That's also a likely cause for your symptoms, and also could be from a new wheel that wasn't properly built.

Check the valve hole - look for sharp edges. Another thing that can come with a new wheel.

If all that looks good, look over the entire rim, searching for something wrong. Are there any cracks? Anything protruding from the inside of the rim that could wear a hole in a tube in a few weeks?

If it's not the rim, something could be embedded in the tire - to find it, remove the tire, then take a cotton ball and, without pushing it hard against the tire body and being sure to always leave a little space between your finger tips and the tire body, rub the cotton ball all over the inside of the tire, in both directions at least.

Things stuck in a tire can be sharp. If you use your finger to look for anything penetrating the tire, you're likely to find it by noting the bloody thing that tore a hole in your fingertip. It's better to find such things by having them catch a few threads from a cotton ball.

Now, that may not find it - something could be embedded into the tire in a way that it only pokes out when the tire is flexed, like when it rolls over the ground. Turn that tire inside out and flex it, and recheck the entire inner surface of the tire looking for cracks or things that poke out or that grab a few threads from your cotton ball.

If all of that doesn't find the problem, get a new tire. In my experience, older tires can lead to frequent flats. You may also simply need more puncture-resistant tires because of how and/or where you ride.

7
  • 7
    Just two small things to add: Maybe OP is using too low tyre pressure and suffering from pinch flats (snake bites). Or maybe their tyres are simply not puncture-proof enough. Highly puncture resistant tyres like Schwalbe’s or Continental’s “Plus” variants would probably be a good idea.
    – Michael
    Mar 19 at 18:46
  • 6
    I'd like to add: One day you will get a sudden flat while riding. It might be cold, raining, with darkness approaching. It's pretty easy to change a tube. Please carry a spare tube and the (minimal) set of tools required. At least then, even if you can't fix it yourself, someone else can help you.
    – Kingsley
    Mar 20 at 22:50
  • 2
    @AndrewHenle don't forget some people are perfectly capable of riding but will never be able to change a tube, at least with roadside tools. The OP mentions an e-bike and I would say they are more common among such riders. I'm not saying this applies to the OP, but I know of some e-bike users who wouldn't be able to get back up off the ground without assistance, but can ride plenty. Of course a good shop should take extra care to look for the root cause, and consider mitigating options like tougher tyres, liners, sealant-filled tubes, and new rim tape
    – Chris H
    Mar 21 at 9:18
  • 2
    With some types of rear wheel it can be harder to get the wheel out (and also back in). For example with fixed gear drives, internal gear hubs, belt drives or hub motors. If you have nuts instead of a quick release lever it will also require suitable tools. IMHO if you have one of these it makes sense to go for really puncture resistant tyres to minimize the chances of suffering one.
    – Michael
    Mar 21 at 13:49
  • 2
    @nightrider if there is "something wrong with your rear wheel", then you should take it to a different shop and have them look into this problem.
    – FreeMan
    Mar 21 at 16:37
19

Additional to Andrew's excellent answer, there's a trick of aligning a label on the sidewall of the tyre to the valve hole.

That way you can remove the tube, identify the hole, and lay the tube on the tyre to show the area where the puncture-causing object is.

Even if you accidentally flip a tube, you will only have two areas to search, at most 2 inches long.

Once you patch the tube (which is a whole separate technique) you have an indication of location, and if there's a future hole in the same spot, then you know the cause is stuck in one place provided the tyre is in the same relative position every time.

If the hole is on the inside-facing edge then you're looking at a spoke that comes through the tape or a burr on a drilled spoke-hole.

The location of the hole in the tube can tell you a lot about the cause.

2
  • 3
    can't believe I've never heard of that: I'll place tyres like that from now on...
    – 2e0byo
    Mar 19 at 23:45
  • 5
    Personally, whenever I'm dealing with a suspected puncture, I always use the yellow marking "crayon" to put a mark on the tyre where the valve is before removing the tyre. Then, when I find the puncture in the tube, I have a pretty good idea where I need to concentrate my hunt on the tyre.
    – Lefty
    Mar 21 at 9:56
1

Put the wheel in a tub of water and watch for bubbles.

2
  • 2
    Welcome to Bicycles! We're looking for answers with more detail. Please consider expanding your answer to further elaborate to specifically suggest strategies for someone experiencing multiple flats. A short answer like this is likely to get downvoted, flagged for moderator intervention, and possibly deleted.
    – Gary.Ray
    Mar 22 at 22:09
  • Further ideas - what are your thoughts on warm vs cold water, and whether one should add a little dishwash/soap, or salt. I've heard both suggested in the past. Use edit to expand the post.
    – Criggie
    Mar 23 at 1:16
1

I brought the wheel with flat tire to the different repair shop where the master looked aged so may be more experienced. I told explicitly that the problem is with the tire periodically getting flat, it is not just about replacing this tube.

I was surprised when I received the mounted wheel back, according to the manometer on my pump (that is old and may not be precise) it was pumped to well over 4 bar (maybe even close to 5 if the reading is correct). I usually run the tires at about 3 bar because there are many postings on the web that MTB tires should run at quite low pressure. I do not know if he has done anything else because I received the wheel assembled.

As it is a rear tire and my speed is almost never above 25 km/h (the engine cut-off), I decided to keep that high pressure, be with it if it fails, not the first time. Maybe I keep getting pinch flats, I have some rough surfaces on my way (gravel joining tarmac, abandoned railway, etc). I observed that the rolling resistance is now much less.

3
  • Older can also means 'stuck in older principles'. I just checked the pressures recommended for the Schwalbe Smart Sam 27.5"-2.35" (just to take a reference of good entry level tires). Maximum recommended pressures are in the 3.5 bars. I invite you to check if you're not way above the recommended levels of the tires.
    – Renaud
    Mar 24 at 9:18
  • I actually really like the reduced rolling resistance. Will be seen. The tire is holding so far. I am not sure what research has actually been done to recommend low pressures. If the tire is not rated, maybe better to buy another tire.
    – nightrider
    Mar 24 at 10:35
  • Let's say that the reasons that lead to pinch flats are the ones that can cause a significant and sudden increase in the tire pressure that can lead in turn to a tire blow-out. It's likely indeed that there is a margin, or that problems will arrive later (a too high pressure can also damage your rims). What tire do you have?
    – Renaud
    Mar 24 at 12:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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