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I am a new bike rider.

Over three months, my wheels are a little bit flat. However I am not too sure as to what pressure I should pump them back up to. Currently they show 25 PSI (172 kPa). It is a hybrid bike I use to ride to work.

Is there any way I can check what the pressure should be? And what is the lowest acceptable pressure that is ok for tires?

  • 2
    what is written on your tires walls ? usually manufacturers write down a suggested pressure on the tires; – Max Aug 5 '18 at 21:41
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    What size are your tyres? Are you light, medium or heavy? Do you ride road or offroad or both? – Criggie Aug 6 '18 at 3:16
  • Is there any way I can check what the pressure should be? Use a pump with a pressure gauge. – Andrew Henle Aug 6 '18 at 9:45
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    @AndrewHenle, no that only shows what the pressure is, what it should be is another question addressed well below. :-) – James Bradbury Aug 6 '18 at 11:41
  • @JamesBradbury Well, if you don't know what the pressure is, you can't adjust it to what it should be. The point being - you have to be able to actually measure the pressure. – Andrew Henle Aug 6 '18 at 13:41
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Each type and size of tire has a different pressure range. The range is written or embossed right on the side of the tire.

The actual pressure you choose is dependent on what you are using the bike for, the road surface you ride on and your general preference. A safe choice the middle of the specified pressure range.

Lower pressure will give a bit more comfort, higher pressure gives slightly less rolling resistance. Beware that too low pressure can make the inner tube susceptible to punctures caused by hitting a bump hard (known as 'pinch flats').

  • How is the text formed? Where would it be located? I see writing that says 700c on the side of tire, but other than that I do not see any other writing. I do not own a car either, so I have no idea where any tire writings are – Quillion Aug 5 '18 at 17:38
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    On the sidewall of the tire, often in raised lettering. They can oftentimes be hard to see. A small flashlight or smartphone light can help you find them. If you can find a manufacturer and model designation you can look up the recommended pressure on the manufacturer's website. – Argenti Apparatus Aug 5 '18 at 18:14
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    Yeah, I've never seen a modern tire that did not have the pressure range embossed on the side of it, somewhere. As Argenti says, it can often be hard to find/read, and I keep a small flashlight in my kit specifically for this purpose. – Daniel R Hicks Aug 5 '18 at 18:33
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    And tire pressure can go too high, too. On a rough road, if you're feeling or hearing a buzz or vibration from your tires, you probably would get lower rolling resistance and more comfort from lower pressure. That uncomfortable buzz/noise/vibration is the tire bouncing over the surface instead of rolling over it. Chipseal roads, for example, are really nasty if you're riding a road bike with 700c/23 tires pumped up to 120 PSI/8+ bar. On surfaces like that, 25s at 95 psi/7 bar would not only be much more comfortable, they'd likely roll better, too. – Andrew Henle Aug 6 '18 at 9:57
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    @Quillion it should be something like "Iflate to XX - YY P.S.I." and it is possible it is on one sidewall only and near the rim. Some may have the range in atmospheres (bar) as well. – Crowley Aug 6 '18 at 11:08
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what is the lowest acceptable pressure that is ok for tires?

The lowest acceptable pressure for a tyre on a wheel on a bicycle varies, but will be

  • high enough to not pinch flat on a rock or pothole by letting the rim squid through/around the rubber and hit the ground
  • high enough to not squirm when cornering fast
  • high enough to avoid coming off the rim
  • high enough to stop the tyre sliding around the rim and tearing off the valve

For a 4" fat tyre that might be 5 PSI. For a 2" MTB tyre that might be 20 PSI if tubeless or 35 PSI if tubed. For a road tyre of 28mm that could be 80 PSI, or a 23mm tyre might need 100 PSI to be safe.

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    And tyre pressure has to be checked more often than in 3-months intervals, at least once a week. It's best done with a track pump that has an integrated manometer. A good investment. – Carel Aug 7 '18 at 7:36
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    @Carel You can check it every ride if you know how a well-inflated tire feels, no tools required ;-) – cmaster Aug 8 '18 at 8:37
  • Sea level atmospheric pressure is about 14psi. So I guess tyre pressures are quoted as an amount above atmospheric pressure? – David Richerby Aug 8 '18 at 8:59
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The maximum pressure will be written on the side-wall of the tyre, though it can be rather hard to find as it's just embossed. For a hybrid, I'd probably just pump the tyre up to the point where there's very little give if you squeeze the sidewalls between your thumb and index finger, and not worry about PSI. If you're heavy, though, you'll need higher pressures.

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    The "squeeze test" almost always results in an under-inflated tire. – Daniel R Hicks Aug 5 '18 at 20:27
  • @DanielRHicks Or in over-inflated tires, depending on the one who's doing the squeezing - I always find that my 6.5 bar tires give in way too much when well inflated... – cmaster Aug 8 '18 at 8:41

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