Mystery Flat (sort of)
 

Let me first provide a little context by letting you know I am a novice rider and have just over 100 miles on my first road bike.

So I recently put a new tube on my rear wheel (23-622 tires, 16-622 rims), and have spent the last week riding. A few days before Independence Day, I went out of town for about a week for the holiday. When I got back yesterday, I found that my rear tire seemed to be completely flat.

I took the tire and tube off expecting that I had punctured it and it had leaked out over course of the trip. When I had the tube off, I pumped some air into it just to find out where the leak was so I could inspect it. To my surprise, nothing seemed to be leaking at all. I silenced everything around me and listened, but heard no hissing. I left the tube sitting for several minutes, and when I returned it still seemed perfectly fine and aired-up. So I deflated it, put it back on the wheel, and pumped it up again. It seems fine, even after checking it again this morning.

What could have happened to cause the wheel to go flat? My last ride home from work the previous week had a bit of light off-road terrain, but I don't remember hitting any hard bumps or potholes or anything. Do I just have a very slow leak?

Some leaks use cloaking devices and enter stealth mode just to mess with us. Next time the tube is out, fill up a sink with water, and the tube with air, and slowly rotate the tube under the water. If you have a leak, you'll see air bubbles. Also remember to check the inside of the tire in case something sharp is still there. Good luck.

What kind of tube is it? If it's latex you will lose enough pressure over 24 hours to be VERY noticeable. The standard butyl tube will also diffuse air over time which will also result in a low/flat tyre. This is normal for all tubes. If you use Co2 to fill your tubes it will diffuse even faster. That being said there is a normal rate of air loss and a abnormal rate. My tyres usually lose about 10-20psi/week with butyl. Same per day with latex.

If one tire is flat and the other is not and they have the same type of tires/tubes, then there is likely a slow leak in the tube. Pump it up some more and listen harder. If that doesn't work, dip it in water and look for bubbles. The slow leak was likely caused by a sharp edge somewhere in your tire or rim, so replacing the tube without fixing the problem will just cause another flat.

Had a flat on a weekend ride. After changing tubes got home an pumped up the flatted tube. WTheck could not find a hole. Finally found the tinyest of pinholes in the tube. Keep looking. Last resort is the tub of water to find the hole.

It's most likely a very slow leak. I'd take the tube out, pump it up, and slowly inspect it underwater. Another way is to spray soapy water on it because bubbles will form.

+1

i had one of these. chances are, there's a very tiny piece of wire lodged somewhere inside the tire. get a cotton ball and run it around the tire. when it gets dragged, you'll find the sucker

Great idea!

Instead of using soapy water to find leaks, which seems like a hassle to me, I just pump the thing up and put the tube up to my lips to feel air coming out. Once I'm in the region, if it's too small to see I just pump it up again and use some spit on my finger to find the puncture.

This one is a Michelin AirStop butyl tube, 700x18-23c with a 52mm Presta valve. I pump it up to 130 psi as the tire is marked with this rating, and then I don't regularly check the pressure because my tire pump doesn't seem to do this well (when I put the valve on a full tube's valve, the gauge reads zero, until I start pumping air into it and the gauge starts reading higher; this seems to create a risk of over-inflating while trying to get an accurate gauge reading).

what i always do is let some air out until the pressure is about 50-70 & then pump it back, and i basically do this twice a week. 130psi is awfully high a pressure to run. what does your tire suggest

The tires are marked '130 PSI'. I read at Sheldon Brown's website that the ratings marked on the tire should be safe and usually reflect about half of the actual 'blowout pressure'.[1]

I weigh around 210 and after getting a pinch flat days after getting my first bike and having had no spare tubes at the time, I suppose I've been thinking that slightly over-inflating would be safer flat-wise than under-inflating. It sounds like perhaps I could take it down a bit to 120 or so. What do you think?

[1] http://sheldonbrown.com/tires.html

Thanks for the tip! I'll give that a try.

yes, tubes slowly leak air. that's normal.

the "blow it up and hold it under water" test is the gold standard for detecting a small puncture. if there's any question, just do it.

I top my tires off with air almost every ride. I also think 130 psi is too high, and harsh riding. I don't think 210 is a lot, but maybe check in the clyde's forum for their tire pressure recs?

Alright, I took the tube out and was ready to try the under-water test, but did the lip/face test and finally found a very small puncture. As I hadn't kept track of where the tube was on the tire initially, I spent some time examining both the rim and the tire. I found a tiny little rock-thorn thing sticking through the tire. It didn't seem to be protruding into the tire when I found it (only outside of the tire), but the puncture-to-valve distance seems to match, and it certainly was sharp, and I imagine with 130 PSI and 100-200 pounds of load on it would allow for plenty of opportunity for puncture.

Another little trick for you - make sure the tire is installed so the label is over the valve stem... makes it easier to match up the tube and the tire if you're looking for punctures and both are off the rim.

I run my 700x23 tires at 110 psi and I'm a bit heavier than you are. I also inflate my tires every single time I go for a ride...

I had one of those, a thorn tip buried in the tire, and kept causing a slow leak. It really does help to line up valve/tire label as suggested, and check for those little bits stuck in the tire. I look for holes in the tire on the outside, and turn the tire inside out and flex it while checking the inside.

Also, I doubt the tire pressure contributed to the flat, but 130 is just too harsh of a ride, IMO.

Cheers!