4

I ride a Trek road bike with 25c tires. The recommended pressure on the tire is 100-130 psi. Before I ride I inflate the tires to close to the max pressure no problem and my pump works fine. But after riding around even for just an hour or so, the pressure in both tires is usually down to 80-90 psi. The tires and tubes are brand new so I wouldn't expect them to have any leaks.

Is this normal? Is there anything I can do about it? I live in a major city and most of the roads I ride on regularly are pretty bumpy -- could that be contributing to the problem?

Edit for more details: The tires and tubes are 700x25c Vittoria Rubino Pro, they're both very new (<1 month old). The bike is a Trek Domane AL3 and it's about 4 years old (link is to a newer model, my bike is older). I had been using 28c tires until I just replaced them recently, which is why I never had this problem before (the pressure range for 28c is 80-100 psi).

7
  • 1
    Hi, welcome to bicycles! No, this is not normal. Can you give us some more details that might help get some suggestions? (e.g. What kind of tires, how old they are?) If it's a new bike you should take it to the shop to have them look at it; otherwise there's definitely something that can be done, it's a matter of figuring out what.
    – DavidW
    Apr 12 at 23:01
  • 3
    What about temperature? If you inflate your tires inside the house and then go out where it's 20 degrees cooler the pressure will go down. Apr 13 at 0:58
  • 1
    Don't assume that new tubes are perfect. Sometimes a whole batch is is iffy. Welcome to Bicycles.SE - you know how things work around here.
    – Criggie
    Apr 13 at 3:00
  • 2
    Are you using the valve correctly? Try dunking the tube in a tub of water (bit by bit if it doesn't entirely fit) and watch for bubbles. How are you measuring the pressure? Some pumps steal air from the tire to equalize their internal pressure which could account for the rest of the drop after temperature.
    – MaplePanda
    Apr 13 at 4:25
  • 3
    Thanks everyone for the helpful suggestions and warm welcome. Just pumping up the tires outside rather than inside seems to have taken care of the problem.
    – Adam
    Apr 14 at 18:42
2

When it comes to loss of pressure, the tires shouldn't be the problem unless they have a puncture damaging the tube, in which case it would be more or less a constant loss (not stopping at 80-90 psi) and each time you have a puncture the damage would be different, as well as how the tube reacts. Bicycle model and size of the wheel shouldn't matter.

It could be an issue with the valves, then (I assume your tubes have Presta valves given the high pressure). Presta valves have to be loosened to inflate the tube and then manually closed (screwing the tip on the valve core with the fingers), because they don't always seal by the action of inner pressure like Schrader valves do. That's how the design of Presta valves work and it's normal, but some brands hold more pressure than others with a loose tip. So it could be that the valves are not closed or at least not tightened enough. Simple, but... well it does happen to me all the time!

Or as mentioned in the previous answer, it could be that the valve cores are not mounted properly. They could be loose or have dirt on the o-rings, and in that case the solution would be cleaning and tightening them, or changing them.

1

I recently built a wheelset for Tannus tire liners and studded tires. Then I noticed that both tires lose pressure quite quickly but one of these lost it in a very alarming manner (15% of gauge pressure loss per day).

For the tire that lost pressure not as quickly as the other, I estimate it was caused by the Tannus tire liner compressing due to the high pressure placed on it. Wait three weeks and the pressure loss has reduced to that of an ordinary tire. So it appears the Tannus liner is compressed about as much as it will compress.

For the tire that lost pressure quickly, the cause was mainly a loose Presta valve core. I didn't make it loose, it was that way straight out of the factory. I tightened it with an adjustable wrench and the quick pressure loss reduced to that of an ordinary tire.

So, moral of the story: if you buy an inner tube with a removable valve core, you can't expect the valve core to be fully tightened straight out of the factory.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.