mattscq

So I went for my usual loop today and at the end of it I realized my front wheel had gone flat. Not a huge problem since I had a patch kit and was close to home so I decided to walk home and swap out my inner tube. Seeing that I had the time, I figured maybe I could patch my tube but I couldn't find the puncture so I decided to inflate it a little and put it into a tub of water. No bubbles. I noticed that the tube had been patched before but it seemed otherwise fine. Should I just put the tube back in? Should I retire it and use a new one?

I was also able to ride it for the entire ride (about 18ish miles) and didn't notice an issue until I stopped and decided to head home.

Ideas? Also I've noticed I've been having many more punctures than I used to when I ran GP4000s. I'm on GP5000s now. Maybe I was just lucky before?

MntnMan62

Interesting. I have no answers for you. I am currently riding GP4000s and love them. I now realize that when they are done I'll have to go for GP5000s. I'm not looking forward to that day.

canklecat

Check the valve core. Last time I had a mystery leak with no puncture that I could find, it was a slightly loose valve core. Snugging it down fixed it.That's happened to me with Presta and Schrader valves.

Another mystery leak was at the base of the valve stem. It was nicked by a burr on the rim's valve stem hole. It only leaked at certain angles. I managed to slow it down with a bit of tape, enough to get home.

mattscq

How do you snug it down? It was tightened all the way.

A development: I put the tube back in and reset the tire. While I was pumping I noticed the pressure wouldn't go past like 20 psi and I heard a faint leaking noise. I checked to see the valve connection was properly fitted and tried two different pumps just in case. The leaking noise was loudest in an area about opposite to the valve (if the valve was at 12 o'clock, I'd say the noise was loudest about 5 o'clock). I checked the tire and it isn't breached on the inside and the rim tape is still basically factory fresh. I replaced the tube with a new one and it worked.

I wonder what happened and what the cause was. It's a little weird. I guess I'll have to buy another tube as a spare, but I'd like to diagnose the problem to know how to avoid it in the future. I'd go tubeless if I hadn't just bought these tires a couple of months ago…

Moe Zhoost

You likely have a small pin hole that wasn't apparent with just a slight inflation. Pump it up as full as you dare and try the water again. I actually have greater success in finding a pinhole leak by passing the inflated tube past my ear. Not only is the leak easy to hear, you can sense the puff of air. Once you find it, put a patch on and you're good.

mattscq

I might just try that. What is a possible cause for a micro pinhole?

Question for everyone:

How many patches do you usually do on a tube before you give up on it?

aggiegrads

As long as the patches aren’t overlapping, there isn’t a limit. I have one tube with 7-8 patches.

Bmach

If the stem is slightly bent it can feel tight but not be seated all the way. It happened on my wife’s bike. I could not find the slow leak, then noticed the stem. Straightened it and no more slow leak.

Moe Zhoost

I've used tubes with many, many patches. I use Rema TipTop patches, which I've found to be reliable. In fact, I see no reason to consider a patched tube less reliable than a new tube.

There have been many discussions about this on BF if you want to search. To pre-empt those who may say that tubes are cheap so why go through all the trouble of patching I'll offer that 1) it takes only 10-15 minutes to patch (most of it to find the hole), 2) patches are a fraction of the cost of a new tube, and 3) most importantly, you avoid more mass going into land fills.

Moe Zhoost

To expand on what I said about small holes not being evident by immersing the tube in water, I did an experiment to see how much pressure a bare tube will contain. The answer is not much at all. As you pump, the tube will expand to equalize pressure so that its internal pressure will never exceed a couple of PSI, if that. In my experiment, I pumped up a ~25mm tube so that its cross section diameter was close to 5 inches. Though it was a bulging, fat monstrosity it only registered about 1 PSI on the gauge. The bottom line is that very small pin holes may require a whole lot more than 1 PSI for the leak to be apparent.

Sy Reene

So the above is IMO contradictory and why I don't typically patch.. almost all of my flats have been of the small pinhole variety so actually finding the pinhole in order to patch would take a lot of effort if it's often even possible.

Moe Zhoost

No, not contradictory. I should have said using the water immersion method - not enough bubbles. I have no trouble finding a pinhole by running the well-inflated tube past my ear.

trailangel

Do you have tube with removable valve core, or not?
You snug down the valve core with the ''valve core snugging down tool".... tool

guy153

You rode over a micro pin.

Usually about 5 or 6, or when you get a hole right next to somewhere you already have a patch.

guy153

Much harder on a very windy day next to a busy road though (when one usually doesn't have a bucket of water either). In that case I put the spare tyre in. I usually like to find the hole though so I know which part of the outer tyre to check especially carefully for the sharp object.

canklecat

Last times I had pinhole punctures, about a month ago, were from wires. One appeared to be from a worn out steel belted radial tire. The other was stiffer and copper, probably from some discarded electronic doodad or construction site debris.

Both times the holes were so tiny I didn't bother patching on the spot, as I usually do on solo rides when nobody is waiting. If I can find the puncture easily I won't even pull the entire tube and tire off the rim, or sometimes even pull the wheel off the bike. If the puncture is obvious, I'll just fish out the bit of tube that needs a patch, fix it and go on.

But with those pinholes I couldn't see, hear or feel the air due to heavy wind and ambient noise. So I replaced the tubes and patched the pinholes later at home.