Page 1 of 2 12 LastLast
Results 1 to 50 of 70
  1. #1
    mtbr member
    Reputation: Neela's Avatar
    Join Date
    Jan 2010
    Posts
    191

    Pumping up your Car's tires with a bike pump

    Okay guys, I'm having a huge debate with a guy at autozone...Here it is:

    In passing conversation I told him that I was planning on adding air to my car's tires with my bike pump. He immediately told me that was stupid and dangerous.

    Me: Why dangerous. I could see you saying it'll take a while, but it shouldn't be dangerous.

    Him: Your car weighs over a ton. Each tire holds up a quarter of that. There is no way your little bike pump will be able to withstand that weight.

    Me: The weight should be fully represented by the PSI. My bike pump can go to 150+ PSI I think. My car's tires are at 35 PSI.

    Him: You're forgetting about the weight of the car.

    Me: Nope, it's what's driving the PSI.

    Him: That's just the pressure, what about the weight?

    Me: Arghhhh

    Okay, I'm 90% sure I'm right here, but given how adamant he was that I'd hurt myself and/or my car, I thought I'd check with the gang here. Can you spot any flaws in my logic or did I miss something?

    P.S. In terms of how many more pumps, I'm thinking that given equal PSI, volume differences should drive # of pumps (effort). I estimate my tire has say 5-10x the volume of my bike tire, so adding air should take me ~3-5 min of pumping. Does anyone do this occasionally?

  2. #2
    bicycle rider
    Reputation: morganfletcher's Avatar
    Join Date
    Jul 2005
    Posts
    2,710
    He's an idiot. PSI is psi.

    Morgan

  3. #3
    Dropshot Champ!
    Reputation: redmr2_man's Avatar
    Join Date
    Jun 2008
    Posts
    4,743
    lol arguing with someone at autozone is dumb.

    ps, did you buy the lucas oil treatment and the brake squeal stop paste at the counter too?

    psi is psi, I air up slicks with a bike pump when I don't have a compressor handy. It does take noticeably longer though.

  4. #4
    mtbr member
    Reputation: TheMachinist's Avatar
    Join Date
    Feb 2007
    Posts
    1,203
    I did it for a while before I finally plugged a hole in my tire.

    Autozone employees work there for a reason.

  5. #5
    Medium?
    Reputation: Fast Eddy's Avatar
    Join Date
    Dec 2003
    Posts
    6,723
    "What about the weight?" LOL.

    If you want to return to help him, the weight is spread out over the contact patch of the tire with the ground. The lower the pressure, the larger the contact patch. A 4000lb car with 40psi in the tires will have exactly 100 square inches of contact patch distributed over the four tires.

    If you want to drive that car on the beach, you can lower the pressure in the tires to 20psi and get double the contact patch so it won't sink so far down into the sand. We regularly run 10psi in our tires on Pismo. It's almost impossible to get stuck. You're floating.

    Math is beautiful.

  6. #6
    mtbr member
    Reputation:
    Join Date
    May 2005
    Posts
    1,540
    Good one

    On other side it took me forever to just "add" some air with floor pump when I found slow leak in remote location.
    I used to run tubes like you are, but then I got thorn in my wheel.

  7. #7
    mtbr member
    Reputation:
    Join Date
    Mar 2005
    Posts
    1,022
    Quote Originally Posted by Neela
    P.S. In terms of how many more pumps, I'm thinking that given equal PSI, volume differences should drive # of pumps (effort). I estimate my tire has say 5-10x the volume of my bike tire, so adding air should take me ~3-5 min of pumping. Does anyone do this occasionally?
    Bwahahahahah. Good luck there. Unless it's a little 14" skinny skinny snow tire, it has way way more than 5-10x the volume.

    I pumped up a 16" tire from ~10psi up to ~30psi one time with my old Silca Pista pump and it took forever (had a slow leak from a nail and needed to get the car to the shop). There was a bit of danger ... the pump barrel got too hot to touch after a couple hundred pumps.

    I pump up our wheelbarrows tire with the bike pump these days, and anything bigger gets the compressor.

  8. #8
    ballbuster
    Reputation: pimpbot's Avatar
    Join Date
    Dec 2003
    Posts
    12,702

    The only danger....

    Quote Originally Posted by Neela
    Okay guys, I'm having a huge debate with a guy at autozone...Here it is:

    In passing conversation I told him that I was planning on adding air to my car's tires with my bike pump. He immediately told me that was stupid and dangerous.

    Me: Why dangerous. I could see you saying it'll take a while, but it shouldn't be dangerous.

    Him: Your car weighs over a ton. Each tire holds up a quarter of that. There is no way your little bike pump will be able to withstand that weight.

    Me: The weight should be fully represented by the PSI. My bike pump can go to 150+ PSI I think. My car's tires are at 35 PSI.

    Him: You're forgetting about the weight of the car.

    Me: Nope, it's what's driving the PSI.

    Him: That's just the pressure, what about the weight?

    Me: Arghhhh

    Okay, I'm 90% sure I'm right here, but given how adamant he was that I'd hurt myself and/or my car, I thought I'd check with the gang here. Can you spot any flaws in my logic or did I miss something?

    P.S. In terms of how many more pumps, I'm thinking that given equal PSI, volume differences should drive # of pumps (effort). I estimate my tire has say 5-10x the volume of my bike tire, so adding air should take me ~3-5 min of pumping. Does anyone do this occasionally?
    ... is throwing out your back. You can do it, it just takes a while and a metric buttload of pumpstrokes. I had to do it with my mini spare once. I actually keep a floor pump in my car at all times for riding.


    Quote Originally Posted by redmr2_man

    ps, did you buy the lucas oil treatment and the brake squeal stop paste at the counter too?

    I still can't believe they sell something to intentionally make your motor oil foam up. Oil is a way better lubricant than air.

  9. #9
    Sweater
    Reputation: Buzzaro's Avatar
    Join Date
    Jan 2008
    Posts
    1,763
    I think the weight is factored right into the P in PSI. The real danger in pumping up your car tire with a bicycle pump is some sort of repetitve motion injury like carpal tunnel...

    a 30" car tire thats 8" wide with a 16" rim has a little over 4k in^3 and (assuming your not on a niner) mtb has a 21 inch rim and 26" tires roughly 2.25 wide so should have a volume around 400 in^3. Around 10 times the volume, you'd be pumping forever. The MTB tires are probably even a little less, I just figured them with square shoulders more like a car tire....
    All out of S**** and down to my last F***

  10. #10
    mtbr member
    Reputation:
    Join Date
    Mar 2005
    Posts
    1,022
    Quote Originally Posted by Fast Eddy
    "What about the weight?" LOL.

    If you want to return to help him, the weight is spread out over the contact patch of the tire with the ground. The lower the pressure, the larger the contact patch. A 4000lb car with 40psi in the tires will have exactly 100 square inches of contact patch distributed over the four tires.
    It's probably more complicated than that. A tire with 0psi in it doesn't have an infinite contact patch (or a 1000sq in at 1psi), and a run flat tire can maintain a usable contact patch without air.

  11. #11
    Sweater
    Reputation: Buzzaro's Avatar
    Join Date
    Jan 2008
    Posts
    1,763
    Quote Originally Posted by anotherbrian
    It's probably more complicated than that. A tire with 0psi in it doesn't have an infinite contact patch (or a 1000sq in at 1psi), and a run flat tire can maintain a usable contact patch without air.
    Can you ever really have 0 psi?
    All out of S**** and down to my last F***

  12. #12
    Sweater
    Reputation: Buzzaro's Avatar
    Join Date
    Jan 2008
    Posts
    1,763
    Quote Originally Posted by anotherbrian
    It's probably more complicated than that. A tire with 0psi in it doesn't have an infinite contact patch (or a 1000sq in at 1psi), and a run flat tire can maintain a usable contact patch without air.
    Kidding, of course. I thought PSI was the force exerted on the area of the tire by the gas and not the weight of the item being supported. You know, your tire pressure is the same whether the car (or bike) is airborne or on a workstand or lift or whatever.
    All out of S**** and down to my last F***

  13. #13
    No unpermitted erections
    Reputation: Finch Platte's Avatar
    Join Date
    Nov 2003
    Posts
    12,558
    The handle of the pump will blast out the top, killing you instantly.

  14. #14
    mtbr member
    Reputation: EBrider's Avatar
    Join Date
    Aug 2004
    Posts
    3,403
    Don't forget that most car tires have schraeder valves

  15. #15
    MTB skillz = NADA
    Reputation: GrayBeard Pirate's Avatar
    Join Date
    Dec 2009
    Posts
    725
    Quote Originally Posted by Finch Platte
    The handle of the pump will blast out the top, killing you instantly.
    True, BUT...Air is forced out of the tire through the now busted pump so fast that it creates a tear in the Time Space Continuum that sucks your now deceased body into an alternate, but perfectly identical dimension. There you will no longer be deceased and unable to inflate a car tire with a floor pump. It will, however, take you a really really really long time to inflate the tire. By the way you will have no knowledge of your alleged death in this dimension and no one here will have any recollection of you, so....now you have been warned.
    Since I don't like writing, I don't have a blog to pimp. This space for rent.

  16. #16
    MTB skillz = NADA
    Reputation: GrayBeard Pirate's Avatar
    Join Date
    Dec 2009
    Posts
    725
    Quote Originally Posted by EBrider
    Don't forget that most car tires have schraeder valves
    So does my Rockhopper.
    Since I don't like writing, I don't have a blog to pimp. This space for rent.

  17. #17
    Now wr rollin on a Boom!
    Reputation: archtop44's Avatar
    Join Date
    Oct 2006
    Posts
    282
    Done it! 30psi from dead flat on a Corolla; full size tire, 1980 Medai floor pump. Enough to get to a gas station.

    Works great, just exactly like you know it will. Also a helluva lot o' pump strokes, just exactly like you expect. More of a wrist workout than I would care to experience again, especially post bumpy ride.

    Made me buy one of those little cigarette-lighter plug-in emergency compressors, which of course I've never needed in the 9 years since I bought it.=P

    I never knew about that Time-Space Continuum anomaly, though. Who could predict these awesome things?
    "I think it's cool how the best line is also usually the most beautiful line" --Kurt F, Tamarancho, Safety Meeting

  18. #18
    No unpermitted erections
    Reputation: Finch Platte's Avatar
    Join Date
    Nov 2003
    Posts
    12,558
    Quote Originally Posted by GrayBeard Pirate
    True, BUT...Air is forced out of the tire through the now busted pump so fast that it creates a tear in the Time Space Continuum that sucks your now deceased body into an alternate, but perfectly identical dimension. There you will no longer be deceased and unable to inflate a car tire with a floor pump. It will, however, take you a really really really long time to inflate the tire. By the way you will have no knowledge of your alleged death in this dimension and no one here will have any recollection of you, so....now you have been warned.

  19. #19
    mtbr member
    Reputation: grrrah's Avatar
    Join Date
    Mar 2004
    Posts
    4,192
    Should have asked him if he knew how his hydraulic lift/jacks worked.

    Anyways, IF he was right (which he wasn't), you could have just taken the jack out of your trunk, lifted the wheel off the ground and pumped away.

  20. #20
    MTB skillz = NADA
    Reputation: GrayBeard Pirate's Avatar
    Join Date
    Dec 2009
    Posts
    725
    Quote Originally Posted by Finch Platte
    Sorry....its not riding induced insanity.
    Since I don't like writing, I don't have a blog to pimp. This space for rent.

  21. #21
    mtbr member
    Reputation: maleonardphi's Avatar
    Join Date
    May 2006
    Posts
    593
    As long as the car doesn't run over the pump, you'll be fine.

  22. #22
    Medium?
    Reputation: Fast Eddy's Avatar
    Join Date
    Dec 2003
    Posts
    6,723
    Quote Originally Posted by anotherbrian
    It's probably more complicated than that. A tire with 0psi in it doesn't have an infinite contact patch (or a 1000sq in at 1psi), and a run flat tire can maintain a usable contact patch without air.
    As soon as the tire is flat the place where the metal rim contacts the ground begins to have a very high PSI. Since the rim doesn't deform, the equation is no longer applicable..

  23. #23
    Save Jesus
    Reputation: beanbag's Avatar
    Join Date
    Nov 2005
    Posts
    2,731
    you should have bet him for money

  24. #24
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    195
    Quote Originally Posted by morganfletcher
    He's an idiot. PSI is psi.

    Morgan
    I'm going to rule with the AutoZone guy,

    I beg to differ. There are more energy stored in a tire @ 30 psi then a bike tire @ 30 psi.

    A good example, a garden hose flows at 9 gals per minute. That wont move your car or threw your bike accross the street at that volume. Now compare that to a river flowing 9 gal per minute. Your car will wash away in seconds.

    Given the same PSI, more volume means it's more dangerous.

    PV=nRT ... Pressure X Volume = N (constant since it's air) R (constant since it's air) Temperture (constant since it's at the same time)

    Tire Pressure X Tire Volume = Pump Pressre X Pump Volume ...

    I found someone calculated tire volume to be 10 litres. 1 liter = .264 Gallons to 10 litre is 2.64 Gallons

    Floor bike pump = 24 inches tall by 1 inch cylinder: Volume = pi x radius ^ 2 x height = 3.14 x .5 inch x .5 inch x 24 inches = 18.84 cubic inch : 1 gallon = 231 cubic inches : .08 Gallons

    PV = PV ... tire (30 PSI) X (2.64 Gallons of air in a tire) = bike pump (X PSI) X (.08 Gallons of air in a bike pump).

    Bike pump (X PSI) = 30 PSI X 2.64 Gallons / (.08 Gallons) = 990.0 PSI.

    YES, your pump will handle 990 PSI!!! That's safe. Grab the handle tight.

    How does that involve the car's weight .. If your remove the tire off the car, PSI drops down a bit. I know that on my camper, with empty truck bed, tire pressure is at 60 psi, once the 2400 lbs thing is on, it jumps to 80 psi!!!

    So the AutoZone guys is right!!!

  25. #25
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    195
    Quote Originally Posted by Buzzaro
    Kidding, of course. I thought PSI was the force exerted on the area of the tire by the gas and not the weight of the item being supported. You know, your tire pressure is the same whether the car (or bike) is airborne or on a workstand or lift or whatever.
    The weight of an item will cause the tire to deform ... aka flatten the tire. Since the tire can't expand else where (steel belts reenforcement), it will cause the pressure to increase since it now has less volume with the same amount of air molecules. PV = nrt = PV.

  26. #26
    Master of None
    Reputation: presslab's Avatar
    Join Date
    Jan 2007
    Posts
    1,462
    Quote Originally Posted by SunGuy
    So the AutoZone guys is right!!!
    I can't tell if you're joking or not...

    This is the case where a little math knowledge is dangerous.

    If you take all the air molecules out of the tire and cram them into the bike pump volume, then sure, it will be 990 PSI. But you're not. With each stroke you're putting a little bit of air into the tire at a time. Not all at once, or vice versa. Even if the check valve in the pump broke your pump will be at the same pressure of the tire, 30 PSI.

  27. #27
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    195
    Quote Originally Posted by presslab
    I can't tell if you're joking or not...
    I wasn't joking. I believed the AutoZone guy is right in the theoretical world.

    Quote Originally Posted by presslab
    This is the case where a little math knowledge is dangerous.

    If you take all the air molecules out of the tire and cram them into the bike pump volume, then sure, it will be 990 PSI. But you're not. With each stroke you're putting a little bit of air into the tire at a time. Not all at once, or vice versa. Even if the check valve in the pump broke your pump will be at the same pressure of the tire, 30 PSI.
    I have LOTS of math knowledge. If I only took one more upper division course in college, I would have a minor in Math.

    If the check valve fails, it will equalized to 30 psi OVER TIME, BUT with the instantaneous rush of air into the pump handle, it will fly up and hit you in the face, neck or eye!!! or worst .. BALLS.

    Have mythbuster done this yet? This should be a good episode.

  28. #28
    Pedaler of dirt
    Reputation: marzjennings's Avatar
    Join Date
    Jan 2008
    Posts
    902
    Quote Originally Posted by SunGuy
    I'm going to rule with the AutoZone guy,

    I beg to differ. There are more energy stored in a tire @ 30 psi then a bike tire @ 30 psi.

    A good example, a garden hose flows at 9 gals per minute. That wont move your car or threw your bike accross the street at that volume. Now compare that to a river flowing 9 gal per minute. Your car will wash away in seconds.

    Given the same PSI, more volume means it's more dangerous.

    PV=nRT ... Pressure X Volume = N (constant since it's air) R (constant since it's air) Temperture (constant since it's at the same time)

    Tire Pressure X Tire Volume = Pump Pressre X Pump Volume ...

    I found someone calculated tire volume to be 10 litres. 1 liter = .264 Gallons to 10 litre is 2.64 Gallons

    Floor bike pump = 24 inches tall by 1 inch cylinder: Volume = pi x radius ^ 2 x height = 3.14 x .5 inch x .5 inch x 24 inches = 18.84 cubic inch : 1 gallon = 231 cubic inches : .08 Gallons

    PV = PV ... tire (30 PSI) X (2.64 Gallons of air in a tire) = bike pump (X PSI) X (.08 Gallons of air in a bike pump).

    Bike pump (X PSI) = 30 PSI X 2.64 Gallons / (.08 Gallons) = 990.0 PSI.

    YES, your pump will handle 990 PSI!!! That's safe. Grab the handle tight.

    How does that involve the car's weight .. If your remove the tire off the car, PSI drops down a bit. I know that on my camper, with empty truck bed, tire pressure is at 60 psi, once the 2400 lbs thing is on, it jumps to 80 psi!!!

    So the AutoZone guys is right!!!
    Wow, awesome. A for effort, but E for result. You should check out AutoZone's career site, they may be hiring.
    It's not enough that we do our best; sometimes we have to do what's required.

  29. #29
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    195
    Quote Originally Posted by marzjennings
    Wow, awesome. A for effort, but E for result. You should check out AutoZone's career site, they may be hiring.
    Haha, I guess you're one of those people. You walk into a store feeling all smart like you know something and the sales person walks all over you and makes you feel like a dumbass. Then you go home and spent hours reading everything on the internet and come back trying to show you're smarter. HAHA.

  30. #30
    mtbr member
    Reputation: TheMachinist's Avatar
    Join Date
    Feb 2007
    Posts
    1,203
    Quote Originally Posted by SunGuy
    I have LOTS of math knowledge. If I only took one more upper division course in college, I would have a minor in Math.
    Should have taken that last class.

  31. #31
    fc
    fc is online now
    mtbr founder Administrator
    Reputation: fc's Avatar
    Join Date
    Aug 1996
    Posts
    23,326
    Here is the answer. The PSI does not change when a tire is off the car or when loaded by the weight of the car.

    http://ask.metafilter.com/133237/Is-...ght-of-the-car

    Calculations found that it should rise from 30 psi to 30.3 psi when under the weight of the car. But no one can measure any change at all. The primary reason is the air is not supporting the weight of the car. It's really supporting the tire sidewall which supports the weight of the car.

    But.... don't pump your car tire with your bike pump. Your neighbors will laugh at you, your pump will wear out and your arms will fall off.

    fc

  32. #32
    Save Jesus
    Reputation: beanbag's Avatar
    Join Date
    Nov 2005
    Posts
    2,731
    Quote Originally Posted by SunGuy

    I beg to differ. There are more energy stored in a tire @ 30 psi then a bike tire @ 30 psi.

    A good example, a garden hose flows at 9 gals per minute. That wont move your car or threw your bike accross the street at that volume. Now compare that to a river flowing 9 gal per minute. Your car will wash away in seconds.

    Given the same PSI, more volume means it's more dangerous.

    PV=nRT ... Pressure X Volume = N (constant since it's air) R (constant since it's air) Temperture (constant since it's at the same time)

    Tire Pressure X Tire Volume = Pump Pressre X Pump Volume ...

    I found someone calculated tire volume to be 10 litres. 1 liter = .264 Gallons to 10 litre is 2.64 Gallons

    Floor bike pump = 24 inches tall by 1 inch cylinder: Volume = pi x radius ^ 2 x height = 3.14 x .5 inch x .5 inch x 24 inches = 18.84 cubic inch : 1 gallon = 231 cubic inches : .08 Gallons

    PV = PV ... tire (30 PSI) X (2.64 Gallons of air in a tire) = bike pump (X PSI) X (.08 Gallons of air in a bike pump).

    Bike pump (X PSI) = 30 PSI X 2.64 Gallons / (.08 Gallons) = 990.0 PSI.

    YES, your pump will handle 990 PSI!!! That's safe. Grab the handle tight.
    There appears to be a fundamental misunderstanding of physics here. When you connect the pump to the tire, the pressures become equal, not the energy. Saying P1V1=P2V2 is wrong. Gas does not flow from low PSI to create high PSI. The pressure in the pump will not exceed the original PSI of the tire. I feel dumber for having had to explain this.

  33. #33
    CHOCOLATE NASTIES Baker
    Reputation: tsimbu's Avatar
    Join Date
    Jan 2005
    Posts
    1,289
    Quote Originally Posted by SunGuy
    If the check valve fails, it will equalized to 30 psi OVER TIME, BUT with the instantaneous rush of air into the pump handle, it will fly up and hit you in the face, neck or eye!!! or worst .. BALLS.
    WOW...just WOW!

    So imagine this.
    A car on the ground with tires inflated to ~35psi.
    I take the valve out of the valve stem. Air starts rushing out.
    If I put my thumb over the valve stem opening are you saying that this ENORMOUS amount of energy will blow a hole through my thumb?

    Force = Pressure x Area
    35PSI on the 1/2" diameter plunger of the bicycle pump will only exhibit ~ 7lbs of force.
    As for the 1/4 hole of the schrader valve...about 1.7 lbs of force.

    "But what about the weight?!?!?" Ha ha ha
    Master of the unintentional track stand.

  34. #34
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    195
    Quote Originally Posted by beanbag
    There appears to be a fundamental misunderstanding of physics here. When you connect the pump to the tire, the pressures become equal, not the energy. Saying P1V1=P2V2 is wrong. Gas does not flow from low PSI to create high PSI. The pressure in the pump will not exceed the original PSI of the tire. I feel dumber for having had to explain this.
    I did misuse the equation. If you feel dumber, I feel dumbest (or most dumb). Life goes on!

  35. #35
    Master of None
    Reputation: presslab's Avatar
    Join Date
    Jan 2007
    Posts
    1,462
    Quote Originally Posted by SunGuy
    I did misuse the equation. If you feel dumber, I feel dumbest (or most dumb). Life goes on!
    Props to you for admitting your mistake.

  36. #36
    mtbr member
    Reputation:
    Join Date
    Aug 2010
    Posts
    195
    Quote Originally Posted by tsimbu
    WOW...just WOW!

    So imagine this.
    A car on the ground with tires inflated to ~35psi.
    I take the valve out of the valve stem. Air starts rushing out.
    If I put my thumb over the valve stem opening are you saying that this ENORMOUS amount of energy will blow a hole through my thumb?
    Haha. I was so stuck in the math and used the wrong equation, I didn't even think about this.

    I used a friend's tire machine last month to install a set of tires and I had to use my thumb to cover the valve stem after seating the bead. Yes, I still have my thumbs.

    Damn AutoZone guy got me. Homedepot/Lowes guys get me all the time. Yes, I also one of those guys I get out of these stores and spent hours on the internet afterwards.

  37. #37
    mtbr member
    Reputation:
    Join Date
    Oct 2005
    Posts
    46

    bike pump = cross training

    I have and air compressor, but I always use a floor pump if I'm only topping off a few psi.

    Perfect upper body workout for my spindly biker arms!

    You should bring in your mini Zefal to the Auto Zone and tell him you use that - he would

    really be impressed.
    American River Canyon

  38. #38
    aka dan51
    Reputation: d-bug's Avatar
    Join Date
    Mar 2005
    Posts
    5,905
    I've used my bike pump while at a gas station to pump up my car tires; the station didn't have a compressor. And like Francis said, I was made fun of. But at least I got my tire inflated.

  39. #39
    native.
    Reputation:
    Join Date
    Mar 2010
    Posts
    64
    Did the guy at Autozone know which aisle the blinker fluid is? I've been told that since my truck is 19 years old, it needs a topping off...

  40. #40
    fc
    fc is online now
    mtbr founder Administrator
    Reputation: fc's Avatar
    Join Date
    Aug 1996
    Posts
    23,326
    Quote Originally Posted by d-bug
    I've used my bike pump while at a gas station to pump up my car tires; the station didn't have a compressor. And like Francis said, I was made fun of. But at least I got my tire inflated.
    i know my schit

    <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/lzzzGgDi8d0?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/lzzzGgDi8d0?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>
    <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/YKr--HAFW6M?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/YKr--HAFW6M?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>
    <object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/lWsSyGiZbHY?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/lWsSyGiZbHY?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

    there's a ton more on youtubes but let me stop there.

    fc

  41. #41
    fc
    fc is online now
    mtbr founder Administrator
    Reputation: fc's Avatar
    Join Date
    Aug 1996
    Posts
    23,326
    Btw, it is illegal to charge for compressed air in CA gas stations. So although the tire pump machines ask for 2 quarters, you can go inside and ask the attendant for tokens for the tire pump.

    fc

  42. #42
    mtbr member
    Reputation: Jack Burns's Avatar
    Join Date
    Nov 2005
    Posts
    1,092
    Once a volunteer trail worker had a flat when we got back to the cars (from driving like a the devil in rental car up the canyon after a storm - long story) and when we discovered it was flat we were three guys and the lady with the flat, and a bike pump.

    I can't remember how we plugged the leak. Or was the spare flat...

    We pumped up the tire in relay using a floor pump. It took us about ten minutes. I remember that. The fatigue was incredible. That's what I remember.

  43. #43
    mtbr member
    Reputation: BitterDave's Avatar
    Join Date
    Nov 2007
    Posts
    428
    Quote Originally Posted by beanbag
    There appears to be a fundamental misunderstanding of physics here. When you connect the pump to the tire, the pressures become equal, not the energy. Saying P1V1=P2V2 is wrong. Gas does not flow from low PSI to create high PSI. The pressure in the pump will not exceed the original PSI of the tire. I feel dumber for having had to explain this.
    I would listed to beanbag, he's a scientician. I saw him pump up a car tire with a bike pump and nothing bad happened, except that his seat post broke several days later. Draw your own conclusions...

  44. #44
    Gravity's Gone
    Reputation: nankerphelge's Avatar
    Join Date
    Jan 2008
    Posts
    1,384
    Quote Originally Posted by francois
    Btw, it is illegal to charge for compressed air in CA gas stations. So although the tire pump machines ask for 2 quarters, you can go inside and ask the attendant for tokens for the tire pump.

    fc
    I've heard the same thing about those machines here in Pennsylvania. A friend of mine told me that it holds true anywhere in the country - not just PA or CA. I've never tried it though.

  45. #45
    Sweater
    Reputation: Buzzaro's Avatar
    Join Date
    Jan 2008
    Posts
    1,763
    Quote Originally Posted by SunGuy
    I wasn't joking. I believed the AutoZone guy is right in the theoretical world.



    I have LOTS of math knowledge. If I only took one more upper division course in college, I would have a minor in Math.

    If the check valve fails, it will equalized to 30 psi OVER TIME, BUT with the instantaneous rush of air into the pump handle, it will fly up and hit you in the face, neck or eye!!! or worst .. BALLS.

    Have mythbuster done this yet? This should be a good episode.
    You should have taken a details class, the reason retarded explanations make sense is always because there's some detail left out.

    You know the saying: If all else fails....dazzle them with BullS***
    All out of S**** and down to my last F***

  46. #46
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    3,595
    the guy at autozone is correct on the weight if you are planning on lifting the car off the ground before pumping it up with the bike pump.

  47. #47
    aka dan51
    Reputation: d-bug's Avatar
    Join Date
    Mar 2005
    Posts
    5,905
    I bet the opposite thread exists in a car forum somewhere and all the users are saying the bike guy is a dumbass idiot.
    Quote Originally Posted by francois
    i know my schit

    fc
    Nice, the third one is even a Subaru! I really don't see why people get chit for doing it.
    Tire needs air + you have a bike pump = inflated tire.

  48. #48
    singletrack bound
    Reputation: Tone No Balone's Avatar
    Join Date
    Dec 2004
    Posts
    2,498
    This thread brings the "Performance Video" back.....

    "Pumping my tires and lubing my chain"

    anybody?
    Sorrel Seeker !!

  49. #49
    mtbr member
    Reputation: grrrah's Avatar
    Join Date
    Mar 2004
    Posts
    4,192
    For the record, if you pump up to 35psi, you probably are a dumchit. I'd stop at 20 or 25 and roll to a gas station for an air compressor. (unless you are stuck at trailhead or somewhere far)

    next question, how many 16g CO2 cartridges would it take?

    Also thinking about the next Downieville gathering

  50. #50
    fc
    fc is online now
    mtbr founder Administrator
    Reputation: fc's Avatar
    Join Date
    Aug 1996
    Posts
    23,326
    Quote Originally Posted by grrrah
    For the record, if you pump up to 35psi, you probably are a dumchit. I'd stop at 20 or 25 and roll to a gas station for an air compressor. (unless you are stuck at trailhead or somewhere far)

    next question, how many 16g CO2 cartridges would it take?

    Also thinking about the next Downieville gathering
    That's the new Downieville Gathering contest:
    - pump a car tire from 0 to 35 psi
    - every minute that passes, drink a BEER!

    fc

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
  •