Advertise on Bikeforums.net



User Tag List

Page 1 of 2 12 LastLast
Results 1 to 25 of 40
  1. #1
    Senior Member stevebiker's Avatar
    Join Date
    Apr 2012
    Location
    Tammany Trace
    Posts
    171
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Why do bike tires lose air?

    My tires lose 20 pounds after a simple 15-mile ride on a paved bike path. It's easy riding. But they always lose air. My girlfriend's bike tires also lose air. All bike tires constantly leak air, right?

    I have Bontreger Hardcase Race Light tires. There's an inner tube, which I would think would keep air in. Unlike car tires, which don't have inner tubes, yet never lose air.

    Why????

  2. #2
    Senior Member
    Join Date
    Mar 2008
    Posts
    4,386
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    A bike tire/ tube is just a fraction of the thickness of a car tire, and it runs on a higher pressure. Air simply seeps through the rubber. The same happens to your car, but at such a slow rate that you'll be well challenged to notice it.

  3. #3
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,466
    Mentioned
    68 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by dabac View Post
    A bike tire/ tube is just a fraction of the thickness of a car tire, and it runs on a higher pressure. Air simply seeps through the rubber. The same happens to your car, but at such a slow rate that you'll be well challenged to notice it.
    +1, the tubes and tires are porous to air and so they bleed. If you've had a balloon go soft in a day or two you've seen the same effect.

    The rate of bleed depends on the wall thickness and exact material, and on the pressure which acts as a driving force. But the rate of pressure drop depends on one other factor, which is the ratio of surface to volume, As the size increases the ratio decreases so it'll take longer for a fatter tube (of the same material and thickness) to lose the same amount of pressure.

    That's why narrow road tires need to be topped off every day or two, while HP mtn tires might go for a week.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  4. #4
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,201
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by stevebiker View Post
    Unlike car tires, which don't have inner tubes, yet never lose air.
    Car tires do lose air, but with a larger volume and lower pressure they lose at a much slower rate than bike tires. Insufficient air pressure is the most common cause of tread wear on cars and trucks.

  5. #5
    It's MY mountain DiabloScott's Avatar
    Join Date
    Sep 2006
    Location
    Mt.Diablo
    Posts
    5,667
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by stevebiker View Post
    My tires lose 20 pounds after a simple 15-mile ride on a paved bike path.
    All bike tires lose air... but that's way more than you'd get from normal permeation, it's a sign of a pinhole leak somewhere. I'd be really surprised if both your tires and both your GF's tires all lost the same amount of pressure in the same ride. I'd also be really surprised if any individual tire didn't lose the same amount of air in the same amount of time whether you were riding it or not.

    Or it could be that you're introducing error when you measure the pressure loss.
    http://diabloscott.blogspot.com/

  6. #6
    Constant tinkerer FastJake's Avatar
    Join Date
    May 2010
    Location
    Madison, Wisconsin
    Posts
    6,121
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DiabloScott View Post
    Or it could be that you're introducing error when you measure the pressure loss.
    +1

    By the time you burp the valve (if applicable) and stick the pump head on you've lost at least 10 pounds on a narrow road tire.

    If you're really losing 20 pounds every 1-2 hours (15 mile ride...) then your tires would be completely flat in a day and you have a slow leak to address,
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  7. #7
    7-speed doomsday prepper ThermionicScott's Avatar
    Join Date
    Aug 2011
    Location
    CID
    My Bikes
    1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX
    Posts
    8,923
    Mentioned
    12 Post(s)
    Tagged
    0 Thread(s)
    It's a conspiracy -- the CO2 cartridge manufacturers are in cahoots with the tube manufacturers. Leaky tubes sell more CO2 cartridges.
    Quote Originally Posted by chandltp View Post
    There's no such thing as too far.. just lack of time
    RUSA #7498

  8. #8
    It's MY mountain DiabloScott's Avatar
    Join Date
    Sep 2006
    Location
    Mt.Diablo
    Posts
    5,667
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ThermionicScott View Post
    It's a conspiracy -- the CO2 cartridge manufacturers are in cahoots with the tube manufacturers. Leaky tubes sell more CO2 cartridges.
    So... Big Rubber is in bed with Big Gas
    http://diabloscott.blogspot.com/

  9. #9
    7-speed doomsday prepper ThermionicScott's Avatar
    Join Date
    Aug 2011
    Location
    CID
    My Bikes
    1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX
    Posts
    8,923
    Mentioned
    12 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DiabloScott View Post
    So... Big Rubber is in bed with Big Gas
    The scales are falling from our eyes.
    Quote Originally Posted by chandltp View Post
    There's no such thing as too far.. just lack of time
    RUSA #7498

  10. #10
    Geck, wo ist mein Fahrrad Rx Rider's Avatar
    Join Date
    Feb 2012
    Location
    Front Range
    Posts
    715
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by FastJake View Post
    +1
    By the time you burp the valve (if applicable) and stick the pump head on you've lost at least 10 pounds on a narrow road tire.
    If you're really losing 20 pounds every 1-2 hours (15 mile ride...) then your tires would be completely flat in a day and you have a slow leak to address,
    so glad you mentioned that, I was going crazy wondering why some tubes "needed" that and others don't. I was blaming my pump for the issue. giant tubes especially need a burp.

    +1 on the leak.

  11. #11
    Kitten Legion Master
    Join Date
    May 2010
    Location
    Portland, Oregon
    My Bikes
    Fuji silhouette, Dawes SST-aL
    Posts
    876
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Gah, no, you guys have it all wrong!

    It's the Bicycle Tire Air Fairies, stealing your air! The more you have protecting your air the harder it is for the Bicycle Tire Air Fairies to take it. There just isn't a such evil little fairy for cars.

  12. #12
    Senior Member DieselDan's Avatar
    Join Date
    Mar 2003
    Location
    Beaufort, South Carolina, USA and surrounding islands.
    My Bikes
    Cannondale R500, Motobecane Messenger
    Posts
    8,522
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Most people never deal with air pressure in their car tires as oil change shop routinely check tire pressures and top off as needed. Then most of those same people raise he!! with bike mechanics because they don't have this air pressure "problem" with their cars.
    Bikes use brakes to stop.

    If your bike has breaks, don't ride it.

  13. #13
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,466
    Mentioned
    68 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by DieselDan View Post
    Most people never deal with air pressure in their car tires as oil change shop routinely check tire pressures and top off as needed. Then most of those same people raise he!! with bike mechanics because they don't have this air pressure "problem" with their cars.
    You're giving the oil change shop rats too much credit, and also car owners. Most people never notice auto tire pressure drop, it's a slow process and they just drive arounf with soft tires, not know or caring.

    There's a big difference between car and bike tires and it isn't the tires. Most car owners don't care about cars. They just want to get from place to place in comfort listening to a decent stereo. But bike owners are different, at least the ones we see on the forum. They're actually dialed into their bikes, and concerned about every creak or click, and notice things like soft tires.

    Also soft tires are harder on the engine, something that's easier to notice when you're the engine.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  14. #14
    Senior Member
    Join Date
    Jan 2012
    Location
    Spokane, WA
    My Bikes
    Specialized Sequoia Elite/Motobecane Fantom Cross Team Ti/'85 Trek 520
    Posts
    2,244
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by stevebiker View Post
    My tires lose 20 pounds after a simple 15-mile ride on a paved bike path. It's easy riding. But they always lose air. My girlfriend's bike tires also lose air. All bike tires constantly leak air, right?

    I have Bontreger Hardcase Race Light tires. There's an inner tube, which I would think would keep air in. Unlike car tires, which don't have inner tubes, yet never lose air.

    Why????
    I have the same exact tires as you do. Mine are 700x32c sized. I lose about 10 pounds over a month in them. I don't know why but I lose very little in those tires.

    On my other bikes say with 700x23c sized tires, I will lose about 20 pounds within a week or so.

  15. #15
    Senior Member
    Join Date
    Mar 2012
    Location
    NE oHIo
    My Bikes
    Specialized, Trek, Diamondback, Schwinn, Peugeot
    Posts
    280
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I used to be in rubber chemical research and did a lot of testing on componds.

    Tubes are made from Butyl rubber. Its typically impervious to air and holds pressure well. Tubeless tires have a ply of butyl so they can hold air, becuse the other compounds in the "carcass" cant hold air.

    I thnk the older product was made a LOT better than what we have now. Materials in todays product seem to be poor. All you can try is another set of tubes and see what leaks the least. Dont overlook the obvious like a leaky valve. That you can do something about.

    -SP

  16. #16
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    3,239
    Mentioned
    47 Post(s)
    Tagged
    0 Thread(s)
    They want Equality, and will always leave their high pressure job, until,
    they become equal with the outside .. . levelers !

  17. #17
    MIKE is my name! puchfinnland's Avatar
    Join Date
    Mar 2012
    Location
    finland,baltimore
    My Bikes
    hans lutz, , puch mistral ultima,2x Austro Daimler Smoked chrome Ultima,Austro Daimler Mixte,Austro Daimler 531 mixte, flying arrow,F Moser,
    Posts
    2,870
    Mentioned
    11 Post(s)
    Tagged
    0 Thread(s)
    "old tubes are better"

    this is interesting, I have a bike from the 50's and inside tubes are some super soft red tubes, dont know the material but they hold air just fine, 60 year tubes super soft- something has changed.
    My name is Michael, and I am a recovering bike addict, It has been 11 months since I purchased a bicycle for myself..
    (Im bound to fall off the wagon again, its just a matter of time)
    Lord help me!

    "Some cream crackers, a glue *** and a little imagination can turn any domestic cat into a fearsome Stegosaurus."

  18. #18
    Senior Member
    Join Date
    Mar 2008
    Location
    Port Townsend, WA
    My Bikes
    xtracycle, electric recumbent, downtube folder and more
    Posts
    982
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You just need fatter tires. I lose about 5 lbs a month in my tires on my Xtracycle, they are 1.95 running at 60 psi with extra thick inner tubes. I don't care about weight on the Xtra.

  19. #19
    Senior Member Hendricks97's Avatar
    Join Date
    Dec 2011
    Location
    Columbus, Ohio
    My Bikes
    All City Nature Boy, Salsa Ti Fargo, Kona Electric Ute
    Posts
    311
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I ride my Pugsley just about every day, and checked the tires this morning after about a week and a half. I was running 11 in the front and 13 in the back. This morning, it was 7 in the front, and 17 in the back????

  20. #20
    Senior Member rydabent's Avatar
    Join Date
    Apr 2010
    Location
    Lincoln Ne
    My Bikes
    RANS Stratus TerraTrike Cruiser
    Posts
    4,164
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Also some tubes just hold air better than others. We are told that there are less than 5 manuf world wide of bike tires. However I have found that Bontrager tubes seem to leak down less than other brands.

  21. #21
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,466
    Mentioned
    68 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by rydabent View Post
    Also some tubes just hold air better than others. We are told that there are less than 5 manuf world wide of bike tires. However I have found that Bontrager tubes seem to leak down less than other brands.
    Some things are repeated so often that people start believing them as fact. The 5 tire factory myth is one of these.

    There are many more than 5 tire/tube makers. It doesn't matter if you count multiple factories owned by one company as one, there are still plenty more than 5 or 10. However it is true that there are more brands than actual makers. Bontrager is one example. They don't have a factory and their tires and tubes are made by one (or more) of the major producers.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  22. #22
    Senior Member
    Join Date
    Sep 2007
    Posts
    8,611
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by stevebiker View Post
    My tires lose 20 pounds after a simple 15-mile ride on a paved bike path.
    Slow leak (or you are letting air out when you check).

  23. #23
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,466
    Mentioned
    68 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by njkayaker View Post
    Slow leak (or you are letting air out when you check).
    +1, normal bleed is 5-20#s per day or less. Significantly more than that is a leak. Most of these stable, slow leaks are at the valve.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  24. #24
    Senior Member Noize4's Avatar
    Join Date
    Jul 2012
    Location
    Nashville
    My Bikes
    Trek 2.1 Apex, Cannondale Quick 4
    Posts
    190
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I call shenanigans on modern cars riding around with flat tires, unless the owner is just lazy. Most all cars made in 2007+ have TPMS, and even if the tires are uniform, will warn you at 29psi or so. I typically need a cold winter to lose appreciable tire pressue, and never lose a measurable amount for months at a time in my car.
    '12 Trek Madone 4.6
    '12 Giant Escape 0

  25. #25
    7-speed doomsday prepper ThermionicScott's Avatar
    Join Date
    Aug 2011
    Location
    CID
    My Bikes
    1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX
    Posts
    8,923
    Mentioned
    12 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Noize4 View Post
    I call shenanigans on modern cars riding around with flat tires, unless the owner is just lazy. Most all cars made in 2007+ have TPMS, and even if the tires are uniform, will warn you at 29psi or so. I typically need a cold winter to lose appreciable tire pressue, and never lose a measurable amount for months at a time in my car.
    Nobody said "modern."
    Quote Originally Posted by chandltp View Post
    There's no such thing as too far.. just lack of time
    RUSA #7498

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •