Had a second flat within a week and trying to identify the cause. I don’t have a lot of experience with this: could the little edge in the rim (which I’m guessing has always been there though) or the tiny scratch (see photos) be enough to cause the flats? They’re standard Schwalbe tubes, so nothing very light or thin(?). So I’m wondering if the tire itself is the problem but couldn’t find any obvious tears or anything, same with the rim tape…
by louie1118
12 Comments
What type of flats are we talking about? I had the same when I first changed to smaller tyres and tubes, but used the same pressure as for bigger ones, which caused snakebites, or pinch flats to happen twice in a week
Where are the punctures on your tubes? (Line up the valve and see if that can help locate the cause.)
Looks pretty normal to me. You can lightly sand smooth any sharp edges if needed. Make sure to also check the inside of the tire for thorns or other stuff (sweep with your fingers as well; don’t just look).
Best bet is to find where the hole is on the tube and then see where that would be on the rim/tire (or at least one of two places if you’re not sure which way the tube was oriented when it was punctured). Pump up the tube and feel for where the air is seeping out (I find putting it next to my face can be helpful to feel for that). Or inflate and then put under water to look for bubbles if you can’t find it. See where it falls on the rim/tire and look for issues. If you don’t find anything, patch it up and see if and where it happens again.
It could be the cause, if it’s sharp enough. But, it’s unlikely because that part of the rim should rest against the tire, not the tube. It is best to use deductive reasoning to figure out where flats come from.
First, it is very helpful to know exactly how to the tube was seated inside the tire. To do this, many people will line up the valve stem with a logo or other notable feature on the tire, when installing the tire. Another common tactic is to draw a mark on the tire and the rim before removing the tire.
Second, you need to find the puncture in the tube. If you can’t immediately see the puncture, you should coat the tube in soapy water, partially inflate the tube, and look for air bubbles. If you can find the hole, and you know how the tube was seated in the tire, you can find the spot on the tire where the puncture occurred.
Lastly, if there is nothing immediately obviously wrong at the suspected puncture point on the tire, or if you missed the first step, try running a cotton ball along the inside of the tire. If there is a sharp object stuck in the tire, the loose cotton will easily snag on it, even if the object is too small for you to see.
I frequently seen rims with a slight mismatching alignment at the same like this. It’s frequently possible to slightly bend the rim back so that it aligns or take a stone to it and smooth it down.
Another thing you can check on is make sure that your room tape is wide enough.
If you haven’t already, pick up a floor pump with an air pressure gauge, so you can properly inflate the tires to your recommended PSI. A lot of “less-experienced” cyclists will just use the “squeeze test” when checking the air pressure, not realizing that the PSI is less than 30, which can cause snake bite flats fairly often.
I usually suggest checking for the recommended PSI for your tire width, riding type and weight, by using the SILCA calculator.
[https://silca.cc/pages/pro-tire-pressure-calculator?srsltid=AfmBOoqK3zX-ga93VuNB-qR7se0RJgFR7RtrNpcK1uJkKE-jpG1d0I9u](https://silca.cc/pages/pro-tire-pressure-calculator?srsltid=AfmBOoqK3zX-ga93VuNB-qR7se0RJgFR7RtrNpcK1uJkKE-jpG1d0I9u)
Find the hole on the tube.
Match the valve to the valve hole and look there on the rim.
If the hole is on the outside of the tube then there’s something in your tire.
You can sand it if you like
You should be able to tell by where the puncture is. If it’s opposite the valve ( at the rim seam) , that’s your sign.
That rim strip looks too narrow and generally crappy so replace it with a wider cloth one.
There’s a fat, rubber-encapsulated tire bead between the tube and this rim mismatch. For that to be the cause of a tube flat, it’d have to eat through the tire bead first. If the bead of the tire is in good condition, look elsewhere.
For any flat, you really have to inflate the tube and locate the hole. That will tell you the whole story. I’ve had customers have repeated flats because they didn’t check the tube and then trace down the cause of the flat, and a piece of glass or a thorn stuck in the tire casing keeps puncturing every tube they put in it. Or they search endlessly for the thorn, when a snakebite puncture would have told them it was a pinch flat.
As a mechanic I run my finger through the whole tire to look for really really small metal. I’ve found pieces so small that only inflating the tube to a high pressure will flat again and the object is so small that it pierces the tube and deflate slowly over night. I don’t recommend using your fingers but something that would catch an object like a rubber glove. Then use tweezers.