Tubed tires - Why oh why do they leak?

Discussion in 'Hangar Talk' started by Rgbeard, Sep 15, 2021.

  1. Rgbeard

    Rgbeard Pattern Altitude

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    I've never had anyone answer this to my satisfaction yet, and I'm hoping the brain trust here has something to offer.

    Why is it that tubed tires leak so much.

    I add air to our bicycle tires every couple of weeks.
    I add air to the plane tires every couple of months.

    I add air to my auto tires - ummm - never.

    I would think tubed tires would leak EVEN LESS than tubeless but the opposite seems to be true.

    The tube is, in my mind a closed-system with the only in/out to be the Schrader Valve.

    Why oh why? Does the tube itself leak air through the rubber by its nature?
     
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  2. PaulS

    PaulS Touchdown! Greaser!

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    Osmosis. I pump my bike tires before every ride.
     
  3. Mtns2Skies

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    Yes. Everything leaks. Tube is thinner than a tire, so more molecules are able to pass through.
     
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  4. Rgbeard

    Rgbeard Pattern Altitude

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    And Wham - there's the answer I was looking for.

    No one's ever "splained" that to me.

    Thanks.
     
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  5. Dan Thomas

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  6. Tools

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    Hehe... or...

    It’s the Schrader valve. Changed on car every three years max? Changed on bike, NEVER?

    Food for thought.
     
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  7. Coinneach

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    My motorcycle has tubes. They hold pressure just fine.
     
  8. Bill

    Bill Touchdown! Greaser! PoA Supporter

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    Remember, the pressure in a tire changes with ambient temperature. Approximately 1psi pressure change per 10*F temperature change.

    IE, a car tire at 35psi at 85 degrees will have ~32psi at 55 degrees.
     
  9. Lachlan

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    Michelin AirStops in the airplane and the tubed bicycle tires. Can’t bear em.
     
  10. NoBShere

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    maybe there is a leaky valve from time to time. As a mountain biker, when i ran tubes i don't know if i ever had a tube last a full year due primarily to pinch flats. After switching to tubeless years ago, i still need to add air before most rides multiple times per week. btw, i switch the valve every time I replace a tire, greater than once per year.
     
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  11. mondtster

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    You obviously live in a place where ice melt isn’t used on the roads with any regularity. Tubeless tires will leak too due to corrosion on the sealing area and there’s nothing to do to fix it except eventually replacing the rims.

    Some tubes retain air better than others. I have motorcycle and airplane tubes I only service twice a year. I have others that need air every time I use the equipment. The thickness and quality of the tubes seems to be the determining factor.
     
  12. FORANE

    FORANE En-Route

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    Yes, those do make a difference.
    One can buy better valves also. The rated psi varies greatly between valves.
    https://schrader-pacific.com/content/uploads/2020/08/Valve-Core-Brochure.pdf
     
  13. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

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    More of a problem with alloy wheels than cheap steel rims.
    Clean (stainless wire brush), prime (zinc chromate and/or zinc phosphate), paint the inside. Problem solved for a long time.
     
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  14. RussR

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    Never? Do you check them periodically? Someone must be putting air in them - if you take the car in for regular service it may be done then.

    My brother showed up at my house one time with about 10 psi in one of his tires. it was almost rolling on the rim. Yeah, he never put air in them either...
     
  15. flyingbrit

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    I've had automobiles with tube and tubeless tires and never noticed much difference in normal leakage. Get a puncture though and the tube tire will usually deflate very quickly while the tubeless usually deflates slowly.
    There is plenty of evidence that tubeless tires do leak. First, the purveyors of nitrogen fills like to claim that nitrogen leaks slower than air so there must be a customer perception that tires leak. Second, all new cars sold in USA since 2010 or so must have tire pressure monitoring systems. (Thanks Ford and Firestone!).
    Leakage in bike tires is very noticeable because of the high pressure and skinny tires (higher surface area to volume ratio). Heck, if I check my bike tires with a standard pencil type gauge the pressure drops just from the air lost during the measurement.
     
  16. Tools

    Tools Pre-takeoff checklist

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    I’ve aired up my Piet tires, motorcycle front wheel x 2, like twice in ten years. Can’t keep air in a wheel barrel or furniture dolly tire to save my soul... very random.
     
  17. MooneyDriver78

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    Michelin Airstops work fine below 35 psi but my front tire is inflated to 49 psi and will lose air.
     
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  18. mondtster

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    Yep. Unfortunately, alloy wheels are nearly standard issue now.

    Some of mine are so bad that I could fill the tire today and 3-4 days later it would be nearly flat.
     
  19. Charlie Golf

    Charlie Golf Line Up and Wait

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    They're that bad?? :)
     
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  20. PaulS

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    My mechanic fixes alloy wheels with bead issues, he grinds them with a wire wheel, and maybe a grinder on the sealing surface, then uses a sealer compound when he puts the tire back on, works great.
     
  21. MauleSkinner

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    I’ll take “they don’t hold air” for $1000 please. ;)
     
  22. Stewartb

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    Tube are porous. Guys got tired of Bushwheels slowly bleeding pressure so now it's standard practice to add a shot of Stan's No Tubes or Orange Seal tire sealant to new tires. Do it once, problem solved forever.
     
  23. Dan Thomas

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    Except that it will cause more trouble later on. Wire wheels leave tiny bits of iron embedded in the aluminum, starting galvanic corrosion. One of the first things one learns in aircraft maintenance training is that you never use a steel wire brush or Emery cloth on any aluminum. Emery is the black stuff and has iron in it. Aluminum oxide cloth is the stuff to use.
     
  24. PaulS

    PaulS Touchdown! Greaser!

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    It might have been an Emory wheel, I didn't watch that closely. My car is gone but my wife's car was done 4 years ago, still good.
     
  25. mondtster

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    Ive done it many times because I have to. I’d classify it as “it sort of works” but is far better than it would be otherwise.

    The best thing would be is if we could get the .gov to quit destroying our roads and cars.
     
  26. Lachlan

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    Ooof. I’m dummmer’na boxxa innertubez. I mean, what I meant to say is I can’t bear being without them, I can hardly barely bear the cost. Nope. I’m just dumm. :D
     
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  27. A Martin

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    .

    Several things:

    --- we still have our fathers 1950's era CCM bicycle ... has original tires and tubes and original factory air in them ... never leaked (he rode it a lot)
    --- his Cockshutt 40 farm tractor is 57 years old .... has about 5000 hours on it ... front tires and tubes are original with original factory air ... (rear tires have been changed twice from normal wear)
    --- asked my tire professional and he said old school tubes were made from genuine rubber tree rubber , were more flexible and remained sealed unless punctured.
    --- he said modern tires and tubes often leak because of tiny bits of grit in the valve ... especially bicycles because they are low pressure and valve does not seat tight.
    --- he said go to any gas station and you see the air hose lying on the ground and full of grit which gets into your valve .... he said to buy good quality valve stem caps that have a sealing gasket in them (worked for me)
    --- tired of pumping up my kids bikes and my lawnmower tires I bought that rubberized liquid tire sealant and put some in each ... never leaked again .... even stops leaks around the rim .... dont use on cars or aircraft ... can throw balance way off and tire shops refuse to work on them because it is gummy sticky stuff.

    .
     
  28. Daleandee

    Daleandee Pattern Altitude

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  29. Clip4

    Clip4 Final Approach

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    If your maint shop will let you fill from their nitrogen tank (bleed all existing air first and top off with nitrogen, and always refill nitrogen) they hold pressure longer because no O2 molecules. I have also found you get what you pay for with tubes. (Goodyear).
     
  30. MauleSkinner

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    …and worked a lot better for slingshots.
     
  31. martym

    martym Pre-Flight

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    just wrap it with a covid mask, apparently nothing can get through those . . .
     
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  32. A Martin

    A Martin Pre-takeoff checklist

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    Installing tubes is a black art

    ----tube should be properly sized for the tire ... hardly ever done .... too small requires over inflation to get the tube to fill up the space ... if tube not snug tire-tube friction can cause heating ... if tube too large you get folds and creases which causes early cracking.

    --- done properly first bead of tire on rim ... then carefully push tube in , center stem in hole .... gently inflate a bit ... make sure valve stem remains centered .... deflate and repeat ..... this normalizes the tube fit in the tire ..... then install final tire bead .... again gently inflate and deflate to make sure tube is normalized in the space .... then high pressure to pop bead of tire securely to rim .... deflate and inflate again to proper operating pressure and make sure valve stem remains centered in hole. Use a valve stem cap with a sealing gasket in it.

    --- If you have a choice between a slightly small tube or slightly large go with the large .... that way the tube rests against the tire at all times even at low pressure .... plus tube is not overly stretched which would make it more prone to future leaks.

    Most of this is common sense but hardly ever practiced .

    Worse case scenario is stuff the completely flat new tube into tire and inflate ... this can pinch tube under tire bead if not carefull .... and cockeyed valve stems put lots of strain on tube in that area .... so make sure it is centered.

    .
     
  33. A Martin

    A Martin Pre-takeoff checklist

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    BINGO !!!!! ... you read my mind ..... we always used old fashioned rubber tubes for our slingshots ... very stretchy and lasts a long time.

    Then along came surgical rubber hose which is even better.

    We need to get the surgical rubber factory to make our aircraft tubes .... haaa

    My helicopter has skids and never any flat tires to worry about ... except the dolly moving wheels ... always going flat .... filled them with permanent foam that fork lift operators use because they are always running over nails at construction sites.

    .
     
  34. flyingbrit

    flyingbrit Pre-takeoff checklist

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    All good except you did not mention coating the tube with talc to provide "lubrication" :)
     
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  35. SoonerAviator

    SoonerAviator Final Approach

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    My tubeless setup on my mtb seems to hold air pretty well. I might have to add a bit of air once every 3-4 weeks but they generally seem to hold up well. I'd attribute most of the air loss I do get from having some fairly old tires on it. Need to get a new set, but I haven't been riding it hardly at all this summer.
     
  36. Dan Thomas

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    The absence of oxygen should also help tube life. No oxidation. And nitrogen from a tank will have no moisture in it.

    But. Air is already 78% nitrogen. Paying for straight nitrogen seems dumb.
     
  37. Clip4

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    Never said pay for it.
     
  38. Getonit

    Getonit Pre-takeoff checklist

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    The true problem is you are leaving the summer air in through the winter and vice versa. Get that correct and nitrogen molecules leaking won’t make any difference.
     
  39. Stewartb

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    The reason new cars use nitrogen in tires is to maintain more consistent tire pressures through temp changes, because tires get hot as you drive. I don’t have that problem in my airplanes.

    What do airliners use? They go from sea level to 35,000’ and back with regularity. That’s a different problem to manage.
     
  40. Chip Sylverne

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    Quit with the negative waves, man.