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  1. #1
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    Tire Pressure. Rider Weight. Tire Width.

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    Not sure how accurate this is, but found this guide to tire pressures versus rider weight and tire width:

    Tire Width=20: Pressure(psi) = (0.33 * Rider Weight in lbs) + 63.33
    Tire Width=23: Pressure(psi) = (0.33 * Rider Weight in lbs) + 53.33
    Tire Width=25: Pressure(psi) = (0.33 * Rider Weight in lbs) + 43.33
    Tire Width=28: Pressure(psi) = (0.33 * Rider Weight in lbs) + 33.33
    Tire Width=32: Pressure(psi) = (0.17 * Rider Weight in lbs) + 41.67
    Tire Width=37: Pressure(psi) = (0.17 * Rider Weight in lbs) + 26.67
    So long as the wheels are still turning, life is good.

    Battswebb

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  2. #2
    Join Date
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    Probably a reasonable starting point, which is all a chart like that can ever be. Tire pressure is part of the suspension, and just like setting up any other suspension component, final numbers are going to depend on terrain, riding style and personal preference.

    Kind of interesting though that I like very stiff fork springs in my moto, and I also like my bici tire pressure high ...
    Speed comes from what you put behind you. - Judi Ketteler

  3. #3
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    I like my pressure a little high, too. This will really help me on my cross bike, though. I've been putting it somewhere in the middle of the numbers listed on the sidewall.
    So long as the wheels are still turning, life is good.

    Battswebb

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  4. #4
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    Sep 2013
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    Montreal, QC
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    On my 23mm it should be around 120 but I find it too stiff/bumpy. So I asked husband to drop it and at 110 it is much better. If it was not riskier for flats, I'm sure I'd drop it to 100-105.

    On the 25mm (gatorskin) I keep it as 105. Just good.

  5. #5
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    I just pump my tires up to 100 psi (Gator skins, 23 mm)....
    2016 Specialized Ruby Comp disc - Ruby Expert ti 155
    2010 Surly Long Haul Trucker - Jett 143

  6. #6
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    Quote Originally Posted by azfiddle View Post
    I just pump my tires up to 100 psi (Gator skins, 23 mm)....
    Ha! My Cross bike has 35 mm tires on it. The chart doesn't include that listing, so I decided to use 33.67, which is between the values listed for 32 and 37. More or less. Did I mention I've been approximating the pressure? I've been setting it at 60-65 ish. The result of the above calculations means that I should have inflated the tires to...60.

    Sigh. so much for that.
    So long as the wheels are still turning, life is good.

    Battswebb

    Pinarello Quattro~CAADX~ Zurich Lemond
    Specialized Romin Saddles

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  7. #7
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    My Surly LHT has 26 x 1.5 inch tires that say 70 psi max. It's so new I've only pumped up the tires twice and I can't remember for sure, but I think I put them at 65. That would come out to something like 40??? That seems kind of low....
    2016 Specialized Ruby Comp disc - Ruby Expert ti 155
    2010 Surly Long Haul Trucker - Jett 143

  8. #8
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    Maybe you should just put it on the minimum listed for that tire? You must be petite, then.
    So long as the wheels are still turning, life is good.

    Battswebb

    Pinarello Quattro~CAADX~ Zurich Lemond
    Specialized Romin Saddles

    Surly Krampus!

  9. #9
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    Dec 2010
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    Boise Idaho
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    Pretty much like any chart - a suggested guide. As we all know, rider size, tire width and road condition oh and air temperature will all come into play.
    We were riding rough jeep trails and one of our friends took a nasty crash, the bike hermit felt his tires and immediately let out at least 10 psi if not more. Our friend had a much happier ride once the pressure was reduced, was an ECR with wide tires and he had them at about 35psi and they should have been at about 20 psi for the road.

    I am terrible about not pumping up my Gilles Berthoud tires before a pavement ride and then having to stop and add air
    Sky King
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  10. #10
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    Muirenn- I estimated- but I weigh a little over 120 at the moment. (sadly, up about 10 lbs from when I got to my goal on weightwatchers a few years ago).
    2016 Specialized Ruby Comp disc - Ruby Expert ti 155
    2010 Surly Long Haul Trucker - Jett 143

  11. #11
    Jolt is offline Dodging the potholes...
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    Quote Originally Posted by azfiddle View Post
    My Surly LHT has 26 x 1.5 inch tires that say 70 psi max. It's so new I've only pumped up the tires twice and I can't remember for sure, but I think I put them at 65. That would come out to something like 40??? That seems kind of low....
    I have similar tires on mine, and have pumped them up to just about 70.
    2011 Surly LHT
    1995 Trek 830

  12. #12
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    Not that it has to be this exact, but 35 mm wheels would be:

    Tire Width=35: Pressure(psi) = (0.17 * Rider Weight in lbs) + 34.17

    (Note to self since these are the wheels on my cross bike, 34.17 being halfway between the numbers used to calculate 32 and 37 mm tires ).

    Actually, I mainly posted because I like knowing how those numbers on the sides of tube boxes are calculated. It's good to be able to do things without relying on answers from other people. Never meant this as an absolute guide. Plus, there are probably new riders on here that were just given some arbitrary number when they bought their bikes, and I thought the info could be useful.
    Last edited by Muirenn; 06-04-2014 at 04:13 AM.
    So long as the wheels are still turning, life is good.

    Battswebb

    Pinarello Quattro~CAADX~ Zurich Lemond
    Specialized Romin Saddles

    Surly Krampus!

  13. #13
    Join Date
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    I think it is an excellent post and appreciate the info

    Quote Originally Posted by Muirenn View Post
    Not that it has to be this exact, but 35 mm wheels would be:

    Tire Width=35: Pressure(psi) = (0.17 * Rider Weight in lbs) + 34.17

    (Note to self since these are the wheels on my cross bike, 34.17 being halfway between the numbers used to calculate 32 and 37 mm tires ).

    Actually, I mainly posted because I like knowing how those numbers on the sides of tube boxes are calculated. It's good to be able to do things without relying on answers from other people. Never meant this as an absolute guide. Plus, there are probably new riders on here that were just given some arbitrary number when they bought their bikes, and I thought the info could be useful.
    Sky King
    ____________________
    Gilles Berthoud "Bernard"
    Surly ECR "Eazi"
    Empowering the Bicycle Traveler
    biketouringnews.com

  14. #14
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    Jun 2010
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    For touring, would you add in the weight of the load plus rider weight? So a 140 lb rider carrying 40 pounds of gear would be calculated at 180 lbs?
    So long as the wheels are still turning, life is good.

    Battswebb

    Pinarello Quattro~CAADX~ Zurich Lemond
    Specialized Romin Saddles

    Surly Krampus!

  15. #15
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    If it were me I'd pick something in between, especially on a hardtail/road bike, since in that case luggage is unsprung weight, while the rider's arms and legs provide some suspension.
    Speed comes from what you put behind you. - Judi Ketteler

 

 

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