Flat tires, no puncture, different tubes...whhhhhhhhhyyy

August 13, 2024 6:51 AM

Two different tubes keep going flat with no detectable puncture or rhythm - see inside.

A while ago my front tire went flat overnight. I rode my spare bike for a bit, then got my act together to fix the flat. Inflated the tube, could not find a puncture - not by touch, in water or by hearing. Inflated the tube and left it for a few hours and it did not deflate. (It still hasn't deflated, weeks later.) Put a new tube in anyway since I had one. Carefully examined the tire and finally found a teeny tiny sharp thing embedded, but that did not seem to match up to any puncture.

Both tubes have schrader valves and indeed the wheel won't accept prestas.

Rode around for weeks with no problem, then the tire went flat overnight. Same thing - could not find a puncture or a sharp object in the tire. Inflated the tube and left it for 36 hours and it didn't deflate, so put it back on the bike and left the bike overnight. The bike was upside down, so no weird pressure on the valve.

In the morning, the tire was flat. Pumped it up as an experiment and rode about four miles, stopped at a store. Tire was fine going into the store. When I came out, it had markedly deflated.

The spokes don't SEEM loose, and if it was a spoke, wouldn't there be, like, a puncture?

Why did I ride around for weeks and everything was fine, only to have two deflation incidents?

If it's a valve problem, why did it happen with two tubes and ONLY when they were on the bike?

I am sort of vaguely assuming that it's something about pressure on the valve, but I cannot think what.

If this is something I can fix myself, I'd rather - bike repair time is extremely backed up and expensive locally, and I have fixed many flats and minor issues in the past. (Honestly, it would be cheaper to just buy a completely new wheel, tire and tube if I can't figure this out.)

posted by Frowner to Sports, Hobbies, & Recreation (11 answers total)

This happened to me. There were burrs on my wheels. Worth a look.
posted by Dr. Wu at 7:03 AM on August 13 [2 favorites]

If your valves have removable cores, make sure they're correctly seated. If you have the wherewithal, replace your rim tape and your tire or at least swap the tire out temporarily. In addition to checking the tire and the rim for things that could puncture the tube, like foreign objects (glass, wire, etc. in the casing) and burrs, look for gashes or weak spots in tire's casing or gaps in the rim (a spoke hole that is only 95% covered by rim tape, if you have double-walled rims). Inner tubes hold enough pressure that they can blow out through surprisingly tiny gaps, and it's not always instantaneous upon filling with air.

For what it's worth, I don't trust the "inflate the tube (outside of the tire/wheel system) and leave it overnight" test. A bare inflated tube is holding considerably less pressure than a tube inside a tire.
posted by pullayup at 7:30 AM on August 13 [1 favorite]

I suspect a defective or damaged valve stem. Are the two tubes you refer to both the same brand? If so, I'd try a different brand of tube and see if that solves the problem.
posted by SageTrail at 7:46 AM on August 13

When this happened to me, it turned out my pump was damaging my (presta) valves. I got a fancy new pump that screws onto the valve, and the problem stopped. Those tubes were not repairable.
posted by Hex Wrench at 10:53 AM on August 13

When I had this problem, it turned out I was not seating the tube properly in the tire when I replaced it, and that allowed the tube to be pinched between tire and rim as I inflated.

The trick was inflating the tube a little bit before I reseated the tire on the rim.
posted by jamjam at 11:30 AM on August 13 [1 favorite]

Since you mention inspecting the spokes; do you have rim tape on your wheels? A little extra protection against the tube getting pinched or punctured by a burr, spoke or spoke nipple, etc.
posted by xedrik at 12:34 PM on August 13 [1 favorite]

I was recently having a similar problem. I tried giving the wheels a light sanding, no help. Replaced the ancient rim tape, it's been fine for a couple of months now.
posted by wierdo at 1:22 PM on August 13 [1 favorite]

Something similar happened to me (on and off for a year or so) and it stopped when I reduced the pressure I was inflating them to.
posted by metasarah at 7:48 PM on August 13

I’ve been getting punctures at the valve base when I’ve overenthusiastically inflated the tyre that behave fairly similarly. Am going to use the ‘inflate it in a few separate slightly cautious goes after replacing tube’ rule from now on, since it doesn’t happen when my bike shop guy puts the tube in.
posted by lokta at 5:07 AM on August 14

Another vote for checking that your rim tape is in good shape and properly centered on the rim.
posted by Archer25 at 7:50 AM on August 14

When we'd see these at the shop, it was almost always a teeny tiny wire or piece of glass that didn't actually stick out of the tire unless it was being ridden. Being able to find that tiny hole and line it up is critical to know where to really pore over the tire. If you don't line up the tire logo and the valve, mark the tire where the valve is so you can line it back up once you know where the leak is. I usually would blow up a tube to twice its normal size and hold it in the sink. Some folks like soapy water to make bubbles. I know you tried this, but I wanted to specifically call out that I blew it up way bigger so it gets stressed.
posted by advicepig at 10:51 AM on August 20