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  1. #1
    One more step forward... WJordan's Avatar
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    Air pressure and inner tubes

    Hey guys, I'm 383 pounds and have 26x2.125 tires and 26x2.125/2.35 inner tubes. What air pressure should I use??

    Also, I found I had a flat tire when I went to ride today. Took the tube out and found I had a very tiny split in a seam of the tube.
    Finding the split in the seam gave me a thought. A guy running a local bike shop told me to run 70 air pressure.
    Will, my thought is, because it's in the seam, do I need heavy duty inner tubes or do they even make a heavy duty tube?

    Thanks for any help!
    Last edited by WJordan; 05-14-11 at 11:04 PM.

  2. #2
    Nigel nfmisso's Avatar
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    the recommended tire pressure range is on side wall of the tire. There is a constant battle between Marketing, and Legal over what those numbers should be. Marketing wants as high as possible, Lawyers want no "booms" by a safe margin.

    Typically, I run 5 to 10 % over what is the max recommended on the side wall. For example, on my hybrid I run 70 psi; even though the max recommended on the side wall is 65 psi.

    Inner tubes do not really make a difference.

    Make sure that your rim tape is protecting the tube from all the sharp edges.

    There are "thorn resistant" tubes which are much heavier.

    A seam failure sounds like a manufacturing defect; or the tube is old. Oxygen and UV light degrade the inner tube (and tire) material; so it could just be old.

  3. #3
    Senior Member magohn's Avatar
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    My road tires state 8.5 BAR - I run at around 7.75BAR. I have had two "explosions" of the inner-tubes at higher pressures. One was when I was trying to hit the 8.5 target and the tube blew out like a gunshot next to my ear (I was pumping the tire at the time) - my ear rang for hours afterwards. The second incident was when I was riding uphill and again, the tube exploded and actually blew out the side of the tire. Im a little paranoid on tire pressures now

  4. #4
    One more step forward... WJordan's Avatar
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    Thanks for the reply back, guys! But a bit confused. Pressure stamped on tire says 40 psi. Even if I went up 10% like you say nfmisso, when I park my big ole' butt on my bike, the tires are going to flatten out, right???

    Dang! I can very well understand being paranoid magohn!

    I need to go correct my weight as I made a mistake. Should have been 383.
    ~When I grow up, Gonna get me one of them there fancy road bicycles~


  5. #5
    Nigel nfmisso's Avatar
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    You may want to take another look at your tires; they usually have a pressure range, rather than just one number on them. For example my hybrid's tires (Bell brand from Wal-mart; 26 x 1.75) state 40 to 65 psi.

    When I started on that bike 2 years ago, I was about 400lbs; now about 330lbs. Never got the tires all the way to flat with me on it though I did break spokes - and now I build my own wheels.

  6. #6
    One more step forward... WJordan's Avatar
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    I will have another look. Thanks!

    BTW: Congrats on the weight loss! I'm trying to work on a low carb diet now.
    ~When I grow up, Gonna get me one of them there fancy road bicycles~


  7. #7
    Senior Member zandoval's Avatar
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    You probably already know this but spraying the rim tube and inside of the tire with armor all before mounting will help the tube sit in place properly and help prevent tube pinch...

    BRAVO for getting going at 383 - I remember how hard it was for me to get going at 283...

    Keep those tires pumped up firm what ever you do - If not you could experience wheel as well as tube failure...

  8. #8
    Uber Goober StephenH's Avatar
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    The pressure relates to both the size of the tire and the weight capacity. But for example, most car tires are run at 30-40 psi and hold up 3,000 lbs quite well due to being larger tires. The pressure rating will depend on how the tire is built, and is not the same for all size tires. Bike-shop tires may have a higher rating than Walmart tires, ask and see. If a bike tire is run without enough pressure the usual symptom is a pinch flat where the tube is pinched between the tire and rim and squishes a hole in it. You can't really judge by the way a tire looks, or you'll get paranoid and forever be thinking your tires are squished too much. If they're working okay, they're fine. Tires supporting a 300# rider are going to be squished more than those supporting a 150 lb rider.

    The tube is not intended as a structural component, but just as a bladder. I suspect most "BLAM" tube failures are really an issue of the tire coming off the rim and letting the tube blow out at that point, rather than the tube just letting go itself.
    "be careful this rando stuff is addictive and dan's the 'pusher'."

  9. #9
    One more step forward... WJordan's Avatar
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    nfmisso, I did go look at the tires again. They only have stamped 40 psi. Nothing like # to # psi.

    zandoval, thank you for that info. I have never heard that and will give it a shot.
    I'm just starting a diet. Got to as it's starting to effect me now that I'm getting older. Started riding about a month and a half ago. Joined a gym a week ago and weighted at the gym three days ago. Knew I was a big ole' boy but shocked me to learn much as 383. I know losing this weight will be maybe the hardest thing I've ever had to do, but have to give it my all.

    StephenH, I agree, I keep watching how flattened the tires look with me on it and I have to break that habit and let the air gauge tell me what I need to know. But when I look at the tube, I really feel it is a bad product this time because the pinch or split is in the seam.
    Oh well, It happened, it's fixed and have to see if it does it again anytime soon.

    Thanks everyone for your comments!!
    ~When I grow up, Gonna get me one of them there fancy road bicycles~


  10. #10
    Nigel nfmisso's Avatar
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    it maybe time to look for some different tires. There are literally thousands of choices out there. Currently; I have Bell, Specialized, Kenda and Michelin on different bikes.

    What kind of surfaces do you ride on? With that information, we can make several specific suggestions for you.

    Take a look at this tire:
    http://www.specialized.com/us/en/bc/...ItemId=0&eid=0
    80 psi on 1.95in (50mm) is plenty to support guys our size, and should fit your current rim.
    Last edited by nfmisso; 05-15-11 at 09:07 PM.

  11. #11
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    For our weight, you should be running them at least the max psi. Generally, for those size tires, that will be 65 psi. I normally run my front at 70 psi and the rear at 80 psi as the weight on a bike is generally distributed about 40% front, 60% rear.
    Old steel makes me squeal!

  12. #12
    One more step forward... WJordan's Avatar
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    nfmisso, It has crossed my mind already about some different tires. Thanks for the link. I will have a look!
    I'm only planning to ride on pavement. Asphalt and concrete.

    Arvadaman, It would scare the crap out of me to push 80 psi in my tires. LOL
    I'm running 70 psi in mine and I noticed I got seriously nervous wondering, 'will this tire blow up in my face' ?????
    ~When I grow up, Gonna get me one of them there fancy road bicycles~


  13. #13
    Nigel nfmisso's Avatar
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    On my commuter (27 x 1); I am running 125 psi on the back and 95 psi on the front

  14. #14
    Senior Member cyclist2000's Avatar
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    OP What brand and model tire are you using?
    I don't do vintage, I bought them new, rode them, kept them. Now they are just old bikes
    http://www.flickr.com/photos/bustercrb/sets/72157623483647522/

  15. #15
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    I seem to remember reading somewhere that for optimum results (comfort and speed) the tire should squash 15% when you sit on the bike. Get someone to watch from the side whilst you sit on the bike (holding onto a wall or something).
    Colnago CX-1 Record 11sp. Carbon Epic Expert 29er

  16. #16
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    Quote Originally Posted by nfmisso View Post
    There is a constant battle between Marketing, and Legal over what those numbers should be. Marketing wants as high as possible, Lawyers want no "booms" by a safe margin.
    So true. Back in the 90s there was a Philadelphia edition of Interbike. A friend of mine and I got passes and attended one day. At one point, we talked with a rep from Continental. To our surpise, he told us that the max. pressure stamped on the side of the tire was only 50% of what the tire was engineered to withstand and that the legal department was the driving force behind the lower figure appearing on the tire.

  17. #17
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    I researched this about 2 months ago. These are the best articles I could
    find on the subject. For everyone above 180 lbs it says you should run
    them at max inflation.

    http://www.bccclub.org/documents/Tireinflation.pdf

    http://www.michelinbicycletire.com/m...rpressure.view
    http://www.michelinbicycletire.com/m...essuremtb.view

    Also see the following thread:

    http://www.bikeforums.net/showthread...ight=inflation
    Old steel makes me squeal!

  18. #18
    Nigel nfmisso's Avatar
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    Quote Originally Posted by cyclist2000 View Post
    OP What brand and model tire are you using?
    Bell Kevlar on the front; Specialized Armadillo on the rear.

    The Armadillo is HEAVY, and has a noticeable negative impact on acceleration; but it has very low rolling resistance and is incredibly tough.

  19. #19
    Senior Member zandoval's Avatar
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    Quote Originally Posted by StephenH View Post
    ...The tube is not intended as a structural component, but just as a bladder...
    Technically true and debatable - Further I am not really sure what mathematical ratios apply for strength of a wheel increasing or decreasing with tube pressure...

    I do know that when my tires are pumped up to reasonably higher pressure my wheels are in fact more stable - Two times I have had to re-true my wheels after riding them with low pressure - You can feel the difference immediately by simply testing different pressures in your driveway - When I was slogging my 286# on my old FUJI with old wheels I had to make sure I maintained pressure to the point I would check the pressure half way through my ride - But these are personal lessons learned for a touring FUJI road bike - I do not know if this applies to Mountain bikes or other styles - I did a search and found many threads in this forum about tire pressure but not any specifically to tire pressure increasing wheel strength - Might make a good future thread...

  20. #20
    Nigel nfmisso's Avatar
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    Quote Originally Posted by cyclist2000 View Post
    OP What brand and model tire are you using?
    Front is a Bell Kevlar from Wal-mart (other places have it also).
    http://www.amazon.com/Bell-Sports-In...6138838&sr=1-6

    Rear is a Specialized Armadillo.
    http://www.specialized.com/us/en/bc/...jsp?spid=58015

  21. #21
    Nigel nfmisso's Avatar
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    Quote Originally Posted by zandoval View Post
    ......Two times I have had to re-true my wheels after riding them with low pressure .......
    This an indication that the spokes had insufficient tension, and were not adequately stress relieved after tensioning - not really due to tire pressure.

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