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  1. #1
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    Tire Pressure - Using Less Than Sidewall Markings?

    What are your opinions on using less tire pressure than the range indicated on the tire sidewall?

    As an example, I'm using 26" x 2.24" 52/54 52-559 WTB Mutano Raptor Tires with a sidewall marking of 35-65 PSI. The tire is mounted on a 21 mm rim. The actual mounted tire width is 2.0" which is about 51 mm.

    I just mounted these tires and haven't had time to experiment with the tire pressure yet.

    The total weight of me, my backpack and the bicycle is around 230 lbs.

    One of the online tire pressure calculators suggests using 21 PSI in the front tire and 36 PSI in the rear tire:
    https://docs.google.com/spreadsheet/...Gc&hl=en#gid=0

    This tire pressure calculator suggests using 35 PSI front and 38 PSI rear:
    Recommend Tire Pressure Vittoria

    This calculator suggest using 34 PSI Front 37 PSI Rear
    MTB tech

    I've never paid much attention to the pressure range on the sidewall and have just adjusted the pressure by the way the tires feel on the road, and then once I've determined what I like, measured the pressure for future reference.

    What about the rest of you?

    Scott Novak

  2. #2
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    Tire Pressure - Using Less Than Sidewall Markings?

    Never look at the sidewall, use what works for you and your weight.

  3. #3
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    Terrain usually dictates my tire pressure.

  4. #4
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    Depending on your weight I'd start closer to 30psi. Don't ever use the liability markings on the side to dictate what pressure you run.

  5. #5
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    Tire Pressure - Using Less Than Sidewall Markings?

    Quote Originally Posted by Scott Novak View Post
    What are your opinions on using less tire pressure than the range indicated on the tire sidewall?

    As an example, I'm using 26" x 2.24" 52/54 52-559 WTB Mutano Raptor Tires with a sidewall marking of 35-65 PSI. The tire is mounted on a 21 mm rim. The actual mounted tire width is 2.0" which is about 51 mm.

    I just mounted these tires and haven't had time to experiment with the tire pressure yet.

    The total weight of me, my backpack and the bicycle is around 230 lbs.

    One of the online tire pressure calculators suggests using 21 PSI in the front tire and 36 PSI in the rear tire:
    https://docs.google.com/spreadsheet/...Gc&hl=en#gid=0

    This tire pressure calculator suggests using 35 PSI front and 38 PSI rear:
    Recommend Tire Pressure Vittoria

    This calculator suggest using 34 PSI Front 37 PSI Rear
    MTB tech

    I've never paid much attention to the pressure range on the sidewall and have just adjusted the pressure by the way the tires feel on the road, and then once I've determined what I like, measured the pressure for future reference.

    What about the rest of you?

    Scott Novak
    Read the pressure sticky thread to the top of the forum.

    I rarely use as much as the minimum number on the sidewall.
    mtbtires.com
    The trouble with common sense is it is no longer common

  6. #6
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    Pressure is so subjective, I mean I have a pump that read 10psi less than my pressure gauge, then I got a new pump that read the same as my pressure gauge. Which was right? I have no idea but I calibrated the new pump with the guage settings and moved forward.

    That said I usually feel that if you are touching your rim to an obstacle once a ride you are close to your prefect pressure. Kinda like setting up suspension, if you aren't bottoming your suspension once a ride you aren't using your suspension to its full potential. The best bet is to just reduce your standard pressure 2psi each ride, you might notice a point where I becomes poorly performing or you might notice a point where all of a sudden performance is so much better. The best reason to track tire pressure vs. the pinch and feel way is so that you can always have a predicable performance envelope that you can rely on.

    I have had rides where I flatted and forgot a pressure gauge and so I just pumped up my tire and rode off and had a hair crazy ride because I was 10psi over what I usually ride. Although I suspect this has more bearing on those of us that ride with no suspension vs. suspension bike folks but I still bet it is noticeable with suspension, just maybe less extreme.
    Try this: HTFU

  7. #7
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    Tire Pressure - Using Less Than Sidewall Markings?

    I'm 225 pounds and run 28-30 psi on 2.35 tires. Never pinch flatted.
    Riding slowly since 1977.

  8. #8
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    Re: Tire Pressure - Using Less Than Sidewall Markings?

    I'm 175 lbs and run 60psi on my sb8's and it seems to work fine for me. Gets a little "thin" on traction in the mud but anything less and i feel like I'd bottom the tire out and dent/taco the rim.

  9. #9
    Formerly of Kent
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    You must hate being comfortable, having traction, or riding fast.

  10. #10
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    I kinda figured that most of you would be ignoring the minimum pressure on the sidewalls. But I thought I'd be on the safe side and ask just in case one of you knew of any particular problems using less than the recommended air pressure.

    My tire gauge was allegedly about 2% accurate when new. Of course It hasn't been calibrated, so who knows how accurate it still is.

    I dropped the pressure to 33 PSI front and 38 PSI rear and that seemed to improve the ride as well as make it more stable on the ice ridges.

    Last night with higher pressure in rear tire, my passage over icy spots was a bit hairy as I could feel the rear end sliding around on the ice. Tonight the ride over the ice gave me a secure feeling. I was still cautious over the ice, but it felt stable.

    Just in case someone hasn't seen these links yet:

    Useful tire information:
    Tech Info | Schwalbe North America

    Rolling Resistance versus Tire Pressure:
    Rolling Resistance | Schwalbe North America

    Scott Novak

  11. #11
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    Re: Tire Pressure - Using Less Than Sidewall Markings?

    The only one of those 3 that's a problem for me is the traction.

  12. #12
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    dont worry, traction is so overrated.

    you dont seriously run 60psi offroad do you?

  13. #13
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    Re: Tire Pressure - Using Less Than Sidewall Markings?

    Just be cautious of too low a pressure, I paid for running about 18 psi up front when trying to rail a corner... rolled the bead right out of the tire. Didn't pop the tube though... somehow. I weigh about 210 with gear... i think running ardent 2.25 up front ( don't love it in front... ). I want to go back to that low, but would need to go tubeless prob.

  14. #14
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    My pump w/gauge can't be correct. If i pump it to 30lbs then the tires are too hard. I probably let out another 5lbs and this is where i usually ride with tubes. No issues.

  15. #15
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    Another way that I try to determine optimum street pressure is to look at the tires and see how much is contacting the road. Sometimes the dust on the road will mark the contact area on the tire. Sometimes wet pavement will do the same thing.

    I'm a bit more concerned with rolling resistance on the road, as I'm often making 15-20 miles trips. Off road, or when the road is ice covered I worry more about traction.

    Scott Novak

  16. #16
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    It's entirely OK to stop for a minute and adjust your tire pressure if you ride on and off the road. If you're meticulous with tire pressures, you might make some adjustments anyways because of temperature differences.

    As for the topic, I'm with everyone else: complete disregard to what the sidewall says. I'm light enough not to worry about exceeding anything.

  17. #17
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    Everybody that rides with suspension is carrying a combo shock and tire pump,right?
    Sorry,I just thought about throwing that in the mix in case somebody needs to adjust something during the ride.
    ...Or you could use 2 pumps and/or cartridges, right? LOL
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  18. #18
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    Actually, pressure varying with temperature is a good thing around here.

    When it gets colder there is more likely to be ice on the roads and with the lower tire pressure your traction will improve. It's a somewhat self adjusting mechanism.

    Scott Novak

  19. #19
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    In my experience living above 60th parallel north, the temperature rising above zero only means water on ice (= even more smooth and slippery) and if it's dry, going below zero doesn't make roads more slippery than they already are. Once water is frozen, the temperature (and tire pressure) could drop quite significantly, but at that point lower pressure will not do anything for you except increase rolling resistance. For commuting I keep the tires inflated so that the pressure is higher than I prefer indoors, so outdoors it drops to what I like. For trail riding during winter I set the pressure just before actually beginning the trail. Usually just the commute to the trailhead is enough for the air in the tires to cool down sufficiently.

    EDIT: long story short, the temperature could vary a lot without affecting traction, or the relationship could be inverse.

  20. #20
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    I too have never paid much attention to the minimum sidewall ratings. I do now. I had an incident a few months ago that left me with a broken saddle and a black eye. Running Bontrager 29-4 Team Issue 2.3 tire up front. High TPI count and light for a tire with large knobs that size - about 800 gm. Very supple casing and great grip on hard-pack and loose-over-hard. I had been progressively reducing the pressure each ride, and was down to 24 psi (6 psi below the minimum) and I railed into a hard-pack bermed turn. The tire rolled under, and I went over the bars and over the top of the berm. Tire never burped, just rolled under. It was like hitting a rock, but there were no rocks in the berm. This is a trail I have been riding for years, so it wasn't a new turn or unfamiliar territory. Just too low an air pressure for the circumstances. If you have ever pole-vaulted, that was the sensation. The tire rolled under, much like the pole flexing and bending down. Then the energy is released as it snaps back and a-flying we will go. Unfortunately, I did a face-plant. First time in almost thirty years of mountain biking. So be careful.

    Quote Originally Posted by Scott Novak View Post
    I've never paid much attention to the pressure range on the sidewall and have just adjusted the pressure by the way the tires feel on the road, and then once I've determined what I like, measured the pressure for future reference.

    What about the rest of you?

    Scott Novak

  21. #21
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    Re: Tire Pressure - Using Less Than Sidewall Markings?

    Quote Originally Posted by bigfruits View Post
    dont worry, traction is so overrated.

    you dont seriously run 60psi offroad do you?
    Yes I do. When I run lower psi, I keep bottoming the tire out and smacking the rim. Feels too slow... And when I say I have a problem with traction, I'm really only talking about uphill mashing in sloppy conditions and the rear tire slips.

  22. #22
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    JPhoyle, sounds like you had a too narrow rim for such a wide tire. Sidewall markings can't predict that - if you use a narrow enough wheel, you can roll the tire under even with the tire pumped up to recommended range.

  23. #23
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    My impression is that the ice seems to get slipperier as the temperature drops. But this may be because the tire tread compound becomes harder and less tractive. So a further drop in pressure might help with the traction. But I can't say that for certain as I haven't done any careful testing to back this up. I should pay closer attention to my tire pressure next winter.

    I think it's safe to say that many, if not the majority of people riding off road are using the minimum approved rim width for their tires. Couple that with using very low tires pressures and you may just have a recipe for disaster. People often get by for quite a while using bad practices. But eventually that worst case situation comes up and bites them in the ass.

    Scott Novak

  24. #24
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    Tire Pressure - Using Less Than Sidewall Markings?

    Quote Originally Posted by JPHOYLE View Post
    I too have never paid much attention to the minimum sidewall ratings. I do now. I had an incident a few months ago that left me with a broken saddle and a black eye. Running Bontrager 29-4 Team Issue 2.3 tire up front. High TPI count and light for a tire with large knobs that size - about 800 gm. Very supple casing and great grip on hard-pack and loose-over-hard. I had been progressively reducing the pressure each ride, and was down to 24 psi (6 psi below the minimum) and I railed into a hard-pack bermed turn. The tire rolled under, and I went over the bars and over the top of the berm. Tire never burped, just rolled under. It was like hitting a rock, but there were no rocks in the berm. This is a trail I have been riding for years, so it wasn't a new turn or unfamiliar territory. Just too low an air pressure for the circumstances. If you have ever pole-vaulted, that was the sensation. The tire rolled under, much like the pole flexing and bending down. Then the energy is released as it snaps back and a-flying we will go. Unfortunately, I did a face-plant. First time in almost thirty years of mountain biking. So be careful.
    I run really low pressure without problems most of the time. Certain loose fit rim and tire combos are problematic. I had a bad roll off once and a face plant too. It was one of my worst crashes and it all happen in my driveway!

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