Tire not holding air problem

[darksky]

Wife's new bike hasn't yet been ridden as she recovers from a medical issue. I checked the tires recently and found the rear tire nearly flat. Pumped to up to 40 psi and checked it in a few days, down to about 20 psi. Aired it up again to 40 psi, after five days still at 40 psi. Is it a problem (maybe intermittent) with the valve core? Any opinions and advice appreciated.

 

[6zfshdb]

Your avatar picture looks like a Pedego Boomerang. If so, it uses the same tires as my Pedego Platinum Interceptor. I have 3 of these bikes. Two were shipped with Slime in the tubes and the third without. The Slime tubes hold pressure for months with no noticeable loss. The tires without the Slime loose about 5# per week. The Pedego tubes are thinner than others I've used and some air loss is normal. In your case however, losing 20# in 5 days is excessive. Since the tire appears to be holding after re inflating, it is likely there was debris in the valve which cleared itself. Keep checking to be sure. Use a valve core tool to make sure the core is seated properly. You might also consider adding Slime to your tubes to minimize the issue in the future.

 

[AHicks]

Another vote for Slime. It's easy, cheap, and it works....

 

[MadAmos]

Temperature changes can also be a factor.

 

[Sierratim]

I agree, check the valve core first. I'd pull it, but a bit of Si grease on the gasket, and reinstall with a good amount of finger torque.

If the tire still loses air after a few days, I'd check the tube. The simplest way is to remove it and pump it up. Slowly run your hands over it feeling for a leak. If nothing, hold it close to your face and repeat on all sides. If still nothing, immerse the inflated tube in a bucket of water and watch for bubbles. Be patient, very slow leaks can take a few minutes to form bubbles. In this case, you'll need some weights to hold the tube under water while you go do something fun.

Once you've found the leak, follow any one of a number of online repair videos. I personally like the Park Tool series;

Not all leaks can be patched such as those too close to the valve stem, those too close to an existing patch, etc. It's OK to install a new tube in these instances.

 

[rich c]

Schrader or Presta? I filled a tire with a Presta and the next day it was flat. Found out the valve has a retention nut on it and that had come loose. Soapy water is your friend for tire problems.

 

[darksky]

It's a Schrader. Thanks to all for your advice.