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A few weeks ago I noticed that my bike tube slowly leaked out air over the course of a day or 2. I bought a new tube and it does the same thing. I checked in water and saw no leaks.

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    Likely the valve -- it may not be screwed tightly. Or these are ultra-thin hoity-toity tubes and not intended to hold air for more than about 48 hours. Apr 21 '20 at 20:15
  • I checked the valve and didnt see any bubbles, as for the tube its a amazon.com/dp/B07BHV6NDR/ref=cm_sw_r_sms_awdo_t1_fkm0Cb4R5KFQG
    – Aphrim
    Apr 21 '20 at 20:25
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    Can you say how much pressure you lost over that time? All tubes do leak air. Butyl tubes, which are almost all tubes, should leak them pretty slowly indeed. I've generally needed to refresh my wife's tire pressure slightly every week (adding about 5 PSI). I think light butyl tubes should leak a bit faster. Latex, which I use on my road bike, does leak significantly faster, but I need to add about 5 PSI per day.
    – Weiwen Ng
    Apr 21 '20 at 20:33
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    Ok so I am losing all the air or almost all the air over 24 hours. My front tire does not have this problem. My new and old tube for back tire have this problem
    – Aphrim
    Apr 21 '20 at 20:37
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    OK. You earlier commented you "checked the valve and didn't see any bubbles". I assume you submerged the tube in water. Did you check the whole tube, or just the valve? If the latter, you should check the whole tube. The amount of pressure you're losing is consistent with a slow leak. I've had these before, and you will see a stream of small bubbles if you move the tube slowly.
    – Weiwen Ng
    Apr 21 '20 at 22:49
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9/10 it’s a tiny sharp object like a sliver of wire stuck in the tire. Take the tube out of the tire, pump it up really big, run the tube through your hand until you feel where the air is coming out. Then look at the tire in that spot and find the thing that poked a hole in the tube.

Alternatively, switch to tubeless and don’t worry about small punctures anymore.

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  • Do not run the tyre through your air if you suspect something sharp, check it visually first. You can injure yourself with something rusty or otherwise ugly. It cn be surprisingly large. Check it visually. Compare the leak position on the tube with the corresponding place on the tyre, remember the valve position on the tyre.
    – Vladimir F
    Apr 22 '20 at 6:35
  • Yes. That’s what I meant. Tube, not tire. Oops.
    – Atrox
    Apr 23 '20 at 7:06

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