El Gato27

Recently picked up a used single speed at a garage sale. I replaced the tubes and got a flat because the rim tape was pretty crappy but I didn’t replace it. Replaced the rim tape, patched the flat and all was good for about a week. Woke up to a flat tire. Check for a pinched tube prior to removing, all good. Removed the tube and checked for leaks in a tub of water, no leaks. Rechecked, still no leaks. Inflated the tube some more and rechecked, very slowly, valve stem included, still no leaks on the tube.

I’ve heard of valves being bad, does this sound like a case where I have a bad valve? If so do I have to replace the tube or can valves be replaced/tightened?
Thank you.

ThermionicScott 

Could be a loose or bad valve core. Tools and replacements can be found at car parts stores.

dsbrantjr

It's probably not the valve core, they are very reliable unless loose which doesn't happen often either. Try putting the tube back into the tire, inflate it fully and try the water check again, including the valve.

You can get valve caps which have core tools built in, and a gasket to seal the tube even if the valve leaks. Like these: https://www.grainger.com/product/TRU-FLATE-Sltd-H-V-Cap-1EZF5?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/1EZF5_AS01?$smthumb$

wschruba

I can count on one hand the number of times I've seen a bad valve core be at fault in a Schrader valve (twice in 5 years: once in a suspension valve, and once in a [30 year old] tube). That said, it's going to run you almost as much to buy the pack of valve cores and removal tool as it would to change the tube.

Life is too short...

speedy25

I have had bad ones where either a foreign blob of some kind got stuck in the sealing surfaces or the sealing gasket fell apart. Almost everybody has an old tube sitting around with the valve still in it, so just snag one, or buy an overpriced blister pack of them at the local store. Dont forget the tool for removal/installation.

-SP

D1andonlyDman

A new tube costs about $5. You should buy one.

El Gato27

Yes, I might use a new tube, not very expensive. Would just like to know what is wrong. I reinstalled the tube yesterday and rode around for ~30 minutes w/o any issues. Tire was fine this morning, I did not put the valve caps back on. Any more issues and I go buy a new tube. Just though some one else might have seen this problem. Thanks for all the inputs.

ExpertTools

Keep in mind that you can only inflate a tube by itself a little bit, and when mounted, you can go to a much higher pressure. It may take that higher pressure to cause the leak.

Another tip, is that water by itself is not the best to see a leak. What you need is soapy water. You can mix a small amount of dish soap into a spray bottle full of water, and that will work much better than plain water at finding a leak. Another option that works very well if you're too lazy to mix up a bottle, is to just spray Windex.

miamijim

Pump it up to full pressure and put some spit on the valve core. It'll bubble up if its bad. If you have a removal tool, and the core is leaking, remove it, drip a drop or chain lube on it and re-install. sometimes it works, sometimes it doesn't.


FWIW I've seen a lot of bad loose cores in my time.

KD5NRH

Replace the tube, then take the old one out back and run the lawn mower over it 5-6 times. It will be obvious what's wrong after that.

Actually, my last 3-days-to-flat-with-no-leak-I-could-find tube is currently tied to a post in the garage as a resistance band for morning stretching.

Miele Man

I've had the odd tube with a pinhole so small that I could ride the tire for nearly a day before the pessure dropped too much. Turned outthat in order to find that pinhole I had to really pump the tube up and when placed under water i had to wipe any bubbles off in order to finally find the leak that was VERY SLOWLY making a new bubble.

A tiny pin hole can be cause by a protruding spoke of in a single wall rim, a piece of grit in the rim or under the tire or it can be a burr on the inside of the rim.

Good luck and cheers