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  1. #1
    Senior Member rando's Avatar
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    tire pressure question

    I have 26X1.5 nimbus slicks on my Trek Mtn bike that I use for a commuter. it says 50-80 psi on the sides but I have been pumping them up to 90 psi for the past three months and I love the way they ride. my question is, how much can I pump these babies up before they become unsafe? I've heard people say that you can inflate way beyond what is on the side of the tire but does anyone have any experience or advice on this?
    "Think of bicycles as rideable art that can just about save the world". ~Grant Petersen

    Cyclists fare best when they recognize that there are times when acting vehicularly is not the best practice, and are flexible enough to do what is necessary as the situation warrants.--Me

  2. #2
    These go to 11. DavidLee's Avatar
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    Have a look here.

  3. #3
    Senior Member ken cummings's Avatar
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    Yes you can way overinflate tires. I have seen it done several times, they go Bang. One lady had Slime (tm) in her tire and got sprayed with goo. Yhe other times were with a 4 man record attempt trike using 200 PSI in the tires. Blowoffs during each run. Since there were 4 tires on each axle, no problem. People have been killed by blowoffs of giant mine truck tires. As Sheldon Brown say it does not help much. I run my 50-80 PSI tires at 80-90 as I am big and carry heavy gear.
    This space open

  4. #4
    Senior Member godspiral's Avatar
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    when you look at the bottom of your rear wheel, should you see a small amount of deflection? Can you measure optimal pressure by the amount of squish you put on the wheel?

  5. #5
    Walkafire
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    Quote Originally Posted by rando
    I have 26X1.5 nimbus slicks on my Trek Mtn bike that I use for a commuter. it says 50-80 psi on the sides but I have been pumping them up to 90 psi for the past three months and I love the way they ride. my question is, how much can I pump these babies up before they become unsafe? I've heard people say that you can inflate way beyond what is on the side of the tire but does anyone have any experience or advice on this?


    Forget the tire... I would be more worried about your WHEEL (Rim).

    Depends on how "old" the rim is, if it is fairly new, then go for it. I have split out a rim which I believe was to pumping up the tires over the rated psi.

    Just keep an eye on the side walls of the rim, and go for it. No need to pump up the front that high, you want traction there!


    ** Note: I ran into a Tire Rep from Conti, he told me the way they rate their tire pressures are (basically): They inflate to Blowout, then divide by half and there is the rating. Simple but true.
    So if a tire is rated at 80 psi, means most of the test tires blew out at 160 psi.

  6. #6
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    Mostly it depends on the bead of the tire. What kind of bead do they have?

  7. #7
    Portland Fred banerjek's Avatar
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    Quote Originally Posted by Walkafire
    Forget the tire... I would be more worried about your WHEEL (Rim).

    Depends on how "old" the rim is, if it is fairly new, then go for it. I have split out a rim which I believe was to pumping up the tires over the rated psi.
    A few years ago, I just happened to be riding on overinflated 26X1.5 nimbus slicks on my hybrid. On this particular day, it was especially hot which increased the tire pressure even more.

    When the rim split, it caught immediately on the front brakes and made the wheel instantly stop moving -- an inconvenient thing to happen when you're moving right along. I was lucky enough not to be injured, but having an unrepairable situation more than 12 miles from home was a real PITA.

    I like to ride with high pressures, but I never overinflate. If you want more than 80psi, switch tires. You might want to drop to a narrower width if you're looking for speed.

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