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Road Bike Tubes

Old 01-28-19, 12:56 PM
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bleucheddar
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Road Bike Tubes

My road bike seems to need daily air or something. I'm very new to all of this. My road bike tires always seem to be a bit flatter the next day, but not completely flat. These tires are 27x1 1/4 and the tires (not tubes) say "high pressure" on them. Am I simply not filling them up all the way in the first place? They are brand new gum wall tires and tubes from Amazon.
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Old 01-28-19, 01:04 PM
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It's normal for bicycle tires to lose a bit of air pressure overnight. The greater your tire pressure, the faster it leaks out. Many riders routinely top up their tires before every single ride.
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Old 01-28-19, 07:51 PM
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Originally Posted by Retro Grouch View Post
It's normal for bicycle tires to lose a bit of air pressure overnight. The greater your tire pressure, the faster it leaks out. Many riders routinely top up their tires before every single ride.
+1
It's on a curve.. eg. maybe 5% a day for argument's sake.. 100 to 95, to 90, to 86, to 82 to 79.. diminishing in absolute PSI lost per day..
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Old 01-28-19, 08:05 PM
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The OP's comment "Am I simply not filling them up all the way in the first place?" stands out to me. If you don't know how much air pressure there's in the tires to begin with how can you know how much has been lost? A simple air pressure gauge is low cost and easy to use. Get one, and for the pressure range the tires need.

To go further. Bike tires are designed to be used at a pressure that is generally stated on the tire's side wall. Without a gauge who knows... Andy
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Old 01-28-19, 08:09 PM
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Originally Posted by Andrew R Stewart View Post

To go further. Bike tires are designed to be used at a pressure that is generally stated on the tire's side wall. Without a gauge who knows... Andy
Caveat.. Vittoria has really odd PSI sidewall markings on their road tires vs. everybody else
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Old 01-29-19, 08:18 AM
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Old 01-29-19, 08:59 AM
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Originally Posted by Retro Grouch View Post
It's normal for bicycle tires to lose a bit of air pressure overnight. The greater your tire pressure, the faster it leaks out. Many riders routinely top up their tires before every single ride.
Fick's Law. Plus a little of Le Châtelier's principle. Fick's law says that the stuff will diffuse out. Le Châtelier's principle says that it will keep going until the pressure is eventually equal.
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Old 01-29-19, 11:06 AM
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There are a number of variables in play. Lightweight tubes lose pressure more readily than standard tubes. Latex tubes lose pressure more readily than butyl rubber tubes. An undersize width tube will lose pressure more readily than an appropriate width tube. Tubes inflated with CO2 cartridges will lose pressure more readily than tubes inflated with ambient air.
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Old 01-30-19, 03:33 PM
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Temperature also can have an effect if the bike is stored in a cold location, particularly at this time of year (in North America).

-Will
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Old 02-01-19, 10:47 AM
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Originally Posted by Random Tandem View Post
Temperature also can have an effect if the bike is stored in a cold location, particularly at this time of year (in North America).

-Will
The lower temperature will slow down the diffusion so that the pressure drop is much less.
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