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  1. #1
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    I find tire pressure (40 psi) more fun (trail riding)

    I run 2.1 maxxis pace tires on my 27.5 hard tail (25 lb bike). I weigh 175 lbs. I have maxxis Ikons on order per the advice from another thread. I was out today on hardpack trails and initially has the tires at about 32 psi and I found the bike sluggish and a slog to get around on. I got my pump and went up to 41-42 psi (and also lowered my shock fork psi by 10). The higher PSI was a blast. I could rocket around the trails and found it much more enjoyable. Am I nuts? Everything I read on this forum says that you have to go to 25-30 psi and that higher psi is terrible. I did notice less grip on roots and rocks. There wasn't really more "bounce" since I had lowered the pressure in my front shock. But the higher psi made me willing to ride longer and farther. So am I out to lunch or what?

  2. #2
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    First off, no one talking about ruining psi in the low 20's are riding super skinny tires like yours. A big tire with big rims and low psi will feel the same to the touch as a skinny tire on skinny rims with high psi so talking about psi without knowing the tire and rim size is meaningless.

    Maxxis is notorious for running much smaller than the stated tire width. So those maxxis 2.1" tires are probably more like a 2.0 or 1.9" wide. That is about the width of tire we were running in the early 90's.

    As far as psi, the less volume your tire has the more psi you will need. Since most people are not running 90's width tires and rims, no one is talking about needeing psi above 30. If we were still riding 90's style tires and rims then there would be no way we could run psi in the low 20's.

    Not sure on you rim width, but the skinnier the rim, the less volume, so again you would need to increase the PSI. So if you are running old school tire widths around 1.9" wide on skinny <i20 rims, then you will need to run a similar psi to what we used to run way back in the day 35-45 psi.

    I can tell you the single worst performance robbing aspect of those old school 90's bikes were the skinny rims because they limited the width of tire that could be used and forced us to run tires with small volume which meant we had to run higher psi. Higher psi means more rolling resistance and less traction. This is why wider tire and rims are now popular. We can now run low psi and increase traction while reducing rolling resistance and keep the tire still feeling lively.
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  3. #3
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    It sounds like your rims are 19 or 20mm wide, which means you dont have much choice.
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  4. #4
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    Quote Originally Posted by singletrackmack View Post
    First off, no one talking about ruining psi in the low 20's are riding super skinny tires like yours. A big tire with big rims and low psi will feel the same to the touch as a skinny tire on skinny rims with high psi so talking about psi without knowing the tire and rim size is meaningless.

    Maxxis is notorious for running much smaller than the stated tire width. So those maxxis 2.1" tires are probably more like a 2.0 or 1.9" wide. That is about the width of tire we were running in the early 90's.

    As far as psi, the less volume your tire has the more psi you will need. Since most people are not running 90's width tires and rims, no one is talking about needeing psi above 30. If we were still riding 90's style tires and rims then there would be no way we could run psi in the low 20's.

    Not sure on you rim width, but the skinnier the rim, the less volume, so again you would need to increase the PSI. So if you are running old school tire widths around 1.9" wide on skinny <i20 rims, then you will need to run a similar psi to what we used to run way back in the day 35-45 psi.

    I can tell you the single worst performance robbing aspect of those old school 90's bikes were the skinny rims because they limited the width of tire that could be used and forced us to run tires with small volume which meant we had to run higher psi. Higher psi means more rolling resistance and less traction. This is why wider tire and rims are now popular. We can now run low psi and increase traction while reducing rolling resistance and keep the tire still feeling lively.
    Thanks for the reply. Sorry if I'm being dense, but how does lowering PSI lower rolling resistance? I thought it was the opposite, with a harder tire rolling faster?

  5. #5
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    Lower pressure allows the tire to conform to irregularities instead of bouncing back as the tire strikes them. It's a fine line though, too low and the tire squirms or rolling resistance rises dramatically.

  6. #6
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    Quote Originally Posted by the_joe View Post
    It sounds like your rims are 19 or 20mm wide, which means you dont have much choice.
    I just measured the rims. They are about 30mm.

  7. #7
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    Lower pressure doesn't always mean better.

    I sometimes find around 30 psi to be a much better handling pressure. The tires are designed to have a certain amount of internal support (pressure). If your trails are twisty and windy, higher pressures would allow the bike to roll into corners better. It may also mean that you are able to get your speeds higher, which makes everything easier and more enjoyable.

    Back in the 90's with 26" tubed tires, I ran 28 psi. I currently run ~25 on my Remedy, and ~30 on my Scarp.
    My fat bike, I run roughly 15 psi. People act like I'm stupid for not running 6. Why do I want to feel like I'm riding through oatmeal?

    Low pressure doesn't always = fast.

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    Wide rims don't always mean beastly.

    Sometimes, 100mm travel is the best.
    Sometimes, a rigid means fun and challenge.
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  8. #8
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    I have wider tires, 2.35, so changes how much pressure I need, but I really like mid to upper 20s. Low twenties and the tire is not stable enough in the corners, as I get towards 30 the tires bounce and skip over roots and rocks and becomes difficult to control.

  9. #9
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    Quote Originally Posted by clodiuspulcher View Post
    I just measured the rims. They are about 30mm.
    The inner width is what people tend to go by. My Trek mtb came with rims <17mm inside, and I had to run 30+ psi on 2.2-2.25" tires with tubes just to keep from getting pinch flats. Switching to "i21"(21mm internal) brought that down considerably. On a different frame, now, so it's a different bike, but the exact same tires that I was using 20psi front and 23 rear with on i21 rims are now at 15 and 19psi, respectively, on i29 and i26 rims. The front seems so low it's disconcerting, but every time I put 2-3psi more in, it gets bouncy, and I stop within a mile to drop pressure.
    'Course I've been using the same floor pump all along, and don't have another pump with a pressure gauge to compare it to, so I have no idea if those are my actual pressures. My two shock pumps are 5psi off from each other, and it wouldn't surprise me if my tire pressures are 5psi more than my pump shows. I just know rim width has made a major difference in whatever psi those tires need.

  10. #10
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    All of these tire pressure discussions depend a lot of what tread patterns you run, what kind of dirt or rock surface you have, and of course, tire and rim width, your own weight, your riding style, do you have tubes or not. I get asked a lot by people new to the sport what kind of pressures they should run. I always tell them to pick a pressure where they aren't beating the rim against stuff (usually I look at them, try to guess weight, calculate a PSI, add a couple for safety) and fiddle with it. If that pressure doesn't feel too soft on the trail, let one or two PSI out. If it starts to feel too soft, add a PSI. People have come up with very different pressures when they've come back to me. But that's what makes them happy or confident. So in reality, roll with what you like.

  11. #11
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    All good points above OP, as the saying goes, "Everything is relative" so you comparing your 2.1" tyres on with race thin casings, holds no relation to me riding my 2.35" Tubeless ready tyres, with EXO casing on 29mm internal width rims, on a full sus and that's not taking rider weight into consideration or trail surface. I used to run those sorts of pressures when I started, had too narrow rims, would get pinch flats and tyre would squirm, once I moved to wider rims and thicker casings I could drop my pressures down and grip increased, especially on roots, especially when wet as the tyre could conform around the root.

    In general if you're riding higher speed trails with lot of big, fast corners, you'll want higher pressures as compared to slower, more technical trails.
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  12. #12
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    Quote Originally Posted by OwenM View Post
    The inner width is what people tend to go by. My Trek mtb came with rims <17mm inside, and I had to run 30+ psi on 2.2-2.25" tires with tubes just to keep from getting pinch flats. Switching to "i21"(21mm internal) brought that down considerably. On a different frame, now, so it's a different bike, but the exact same tires that I was using 20psi front and 23 rear with on i21 rims are now at 15 and 19psi, respectively, on i29 and i26 rims. The front seems so low it's disconcerting, but every time I put 2-3psi more in, it gets bouncy, and I stop within a mile to drop pressure.
    'Course I've been using the same floor pump all along, and don't have another pump with a pressure gauge to compare it to, so I have no idea if those are my actual pressures. My two shock pumps are 5psi off from each other, and it wouldn't surprise me if my tire pressures are 5psi more than my pump shows. I just know rim width has made a major difference in whatever psi those tires need.
    I just measured the inside flat part of the rims. On both of my bikes they are about 11mm. So I guess I have <i20 as you said.

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    OP here. How difficult is it to find new wheels with thicker rims that would fit my bike? I assume the axel width is standardized?

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    If you're enjoying your ride more, then the psi is right on It's all personal..sounds like your trails are smooth so no need to worry about lower pressures unless you're losing traction too often. Btw, you're right about rolling resistance.. harder tires will roll quicker but give less traction over bumps etc. That other comment was wrong. You may get through a certain, more technical trail quicker with lower psi but that has nothing to do with "rolling resistance". That's just because the tire conforms to the trail better. Just wanted to clear that up. Anyway, keep having fun out there and make adjustments to what you like, not what the "experts" say. It's definitely all relative.

  15. #15
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    Image below shows internal width (49.9), highly doubt if your rims external width is 30mm that your internal would only be 20mm, that would be 5mm thick sidewalls, highly doubtful unless you're running Vbrakes and even then that's really thick.

    Quote Originally Posted by clodiuspulcher View Post
    I just measured the inside flat part of the rims. On both of my bikes they are about 11mm. So I guess I have <i20 as you said.
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  16. #16
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    Can you tell us what frame and fork you have? That would help in determining what axle widths you have. But don't make changes because someone says you need to..only if for some reason it's holding you back.

  17. #17
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    Quote Originally Posted by clodiuspulcher View Post
    OP here. How difficult is it to find new wheels with thicker rims that would fit my bike? I assume the axel width is standardized?
    There are hundreds of wider rims available these days. There are several axle width and diameter "standards" in the mtb world. Your frame and fork will dictate which axles you need and how wide of rims you can go, so it really depends on what you have.

    In my opinion, running 40 psi on a mountain bike is useless for anything except smooth gravel trails. Lots of people will disagree with me. I'd recommend test riding or demoing a bike with wider hoops to see what theyre all about. Have fun!
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  18. #18
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    Quote Originally Posted by clodiuspulcher View Post
    I run 2.1 maxxis pace tires on my 27.5 hard tail (25 lb bike). I weigh 175 lbs. I have maxxis Ikons on order per the advice from another thread. I was out today on hardpack trails and initially has the tires at about 32 psi and I found the bike sluggish and a slog to get around on. I got my pump and went up to 41-42 psi (and also lowered my shock fork psi by 10). The higher PSI was a blast. I could rocket around the trails and found it much more enjoyable. Am I nuts? Everything I read on this forum says that you have to go to 25-30 psi and that higher psi is terrible. I did notice less grip on roots and rocks. There wasn't really more "bounce" since I had lowered the pressure in my front shock. But the higher psi made me willing to ride longer and farther. So am I out to lunch or what?
    No, you are learning what you like and what you want. Tire pressure is a personal thing that is dependent upon lots of things. I would ride with a guy who would pump up his tires to 40-45 PSI to ride to ride the rockiest trails and ride everything incredibly fast. I was running ~20 PSI on those same trails -with different tires. He could do it and actually liked it better.

    I moved south and the terrain is pretty much flat and hard-packed. I run 45 PSI here but drop down -sometimes to 20 PSI depending upon the terrain.

    Do what you like. Experiment. Don't do what people tell you should be right. Learn and enjoy!
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  19. #19
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    Hasn't been emphasized enough, but rider weight (you plus any clothes and gear you've got on your back) is an EXTREMELY important factor in the equation. The heavier you are, the higher the pressure you'll have to run in your tires to find your sweet spot. What works for me won't likely work for you.

    You do want the tire to deform some around irregularities in the trail. Especially small chattery stuff that suspension usually isn't sensitive enough to absorb. If your trails are lots of hardpack without too many exposed roots, for example, you'll be able to get away with a higher pressure than someone whose trails are through dense forests where the trees have very shallow root systems that get exposed and make for some gnarly root gardens, or someone whose trails have lots of exposed rock (especially if that rock is broken up, and not just smooth slabs).

    My bike has 4" tires on 65mm rims, 110mm suspension on the front and 100mm on the back. I weigh about 180lbs, and am close to 200 all kitted up. Depending on the terrain and conditions, I will run my tires anywhere from 2psi to 9.5psi. That's so extremely different from what you are doing that it's obvious that what I do has absolutely no relevance for you. That also exists to a smaller degree for every other rider out there.

    Here's what I've done to figure out what I like:
    First, I get a separate gauge. I use a Meiser analog one that goes up to 30psi, because it works for my fatbike as well as for my wife's preferences on her 26x2.35" tires on 29mm internal rims. And it's cheap. It stays at home in the workshop.

    Then, I did a little research on tire pressures for my particular setup. I started a little high (it's much less expensive to start too high than too low). I used my gauge to start at something like 12psi for dry trails, I think. That was too hard once I got out onto the trail, so I dropped it until I was happy. If I went too low, I added some air with a pump. Then I checked where I was with tire pressure when I got home. I did this with every new set of conditions or new tire until I had in my head a pretty good idea of what I like under which conditions. So now, when I set my tire pressure before I ride, I have a pretty good idea what I should set it at so I don't have to fiddle as much once I'm on the trail. When I buy new tires, I'll have to reevaluate for the new set. Stiffer or more supple casings will change what I use for tire pressure.

    I even noticed that for 2.2-2.4" tires. I was using light, supple tires at somewhere around 27-31psi for awhile. I got newer tires with MUCH stiffer sidewalls, and I dropped down to around 22-25psi to get the same feel. Same bike, same rider, same trails, same rims, even the same tire brand and tread pattern. Just stiffer sidewalls.

  20. #20
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    40 psi is not outside the realm of possibilities...

    My Ardent Race 2.2 in EXO 3C Maxspeed flavor requires 32 psi to roll how I like.

    My XR4 2.4 team issue rolls best at 24-25 psi.

    My Forekaster 2.35 Exo dual compound is best at 25-26 psi.

    NB, these are all as rear tire setup.

    Up front pressures drop again - e.g. Conti MKII 2.4 Protection is at 18-19 psi. It has 4x layered walls.

    I always go tubed...

    I weigh 245 lb's all kitted up.

    As others have said, the narrower the tyre, the higher pressure it requires.

    This has also been my personal experience.

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    Last edited by targnik; 04-16-2017 at 01:24 PM.
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    Quote Originally Posted by LyNx View Post
    Image below shows internal width (49.9), highly doubt if your rims external width is 30mm that your internal would only be 20mm, that would be 5mm thick sidewalls, highly doubtful unless you're running Vbrakes and even then that's really thick.



    Oh ok, no, the rims are ~30mm then. When you said the inside rim I thought you meant the flat part in toward the wheel spokes.

  22. #22
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    Quote Originally Posted by clodiuspulcher View Post
    Oh ok, no, the rims are ~30mm then. When you said the inside rim I thought you meant the flat part in toward the wheel spokes.
    It sounds like you're fairly new to the sport. What works best for you will change dramatically as the trails you ride and your riding style evolves. I think it's sensible to get the best bike/gear for your local trail systems and set the bike up for that, but always keep in mind that your tastes are going to change as you pack on the miles. Focus on riding your bike, not tweaking your bike.

    On that note, this is a sport with an incredibly long learning curve. It took me >5 years to develop a consistent riding style (and how i ride now is nothing like my first 3 seasons!!!) and then i had to cycle through a bunch of equipment to start to understand tire pressures and suspension set up in a fundamental way. We're all still learning.
    I like cheap stuff that works great and is very sturdy.

  23. #23
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    Quote Originally Posted by clodiuspulcher View Post
    Oh ok, no, the rims are ~30mm then. When you said the inside rim I thought you meant the flat part in toward the wheel spokes.
    It's no wonder you like 40psi on 2.1" tires for rims that wide. 30mm interior width rims work best with wider tires, say 2.3-2.6 or so. With tires that narrow on such wide rims, the sidewall is super straight and the tread squared off. The tire sidewalls have to provide more structural support than usual when set up that way, and will require more pressure to feel supportive enough to avoid rim strikes.

    Your bike probably doesn't corner very well, either. Can't lean it much without running into a hard edge on the tread and eating $hit. You want a nice, round tire profile, so the wider the rim, the wider the tire you want to run on it.

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  24. #24
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    ^^^ word, not a great rim/tire combo
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  25. #25
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    Harold makes some good points on tire pressure and terrain and like many said already, the "right pressure" is the one you choose or experiment with while out riding and testing the areas you prefer unless you are getting pinch flats or banging the rim.

    I rarely ride solo and I prefer riding my own pace, stopping for photos or whatever.. and usually, I fall in as the last position. I have to remind myself that I pick my own line and the rider ahead of me may choose a more technical rooty or difficult part of the trail than I prefer.
    Maybe they are practicing those tech skills or experimenting with tire pressure whereas I might be training my eye to find the easiest path of least resistance and work. (Lazy)
    Keep in mind, every ride can be a level of training and experience that you are adding to your tool box for future reference.

    You can also get/use a better psi gauge for reference sake to check it against the cheaper pencil type gauge or an alternative you can carry with, at least until you get yourself trained on squeezing the tire to estimate pressure.

    Many of the cheap gauges read pretty consistently although not exceptionally accurate. Still, this means you can learn of an offset that enables you check and know the tire ranges such as 15 psi on one gauge may read 12 on the other.... you can still account for that variation.
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  26. #26
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    Some very clear and mature comments being made here. I use tyre sizes at the narrow end of this discussion and find at 2.1" a front/rear combo of 38/42 psi ideal, but factor in my local ride conditions etc as stated above. I also, on the same bike, fit cyclocross wheels with 35mm width and identical brand/tread patterns, and up this to 50/55 psi. Smaller volume, higher pressures, greater speed on the hard pack. This is probably what you are noticing. If I were to go to fatter tyres, I expect that these pressures will need to drop and would decrease them until I found that 'sweet point' balance on my local rides.

    Enjoy your riding.

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  27. #27
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    Shucks, we all ran 40psi and 2.1" tires back in the late 90's. Nobody died. (that I know of) PSI requirement/preference is like any aspect of bike set-up: highly variable depending on terrain, trail surface/quality, rider weight, rider style, tire size and design, etc, etc.

  28. #28
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    Quote Originally Posted by Harold View Post
    It's no wonder you like 40psi on 2.1" tires for rims that wide. 30mm interior width rims work best with wider tires, say 2.3-2.6 or so. With tires that narrow on such wide rims, the sidewall is super straight and the tread squared off. The tire sidewalls have to provide more structural support than usual when set up that way, and will require more pressure to feel supportive enough to avoid rim strikes.

    Your bike probably doesn't corner very well, either. Can't lean it much without running into a hard edge on the tread and eating $hit. You want a nice, round tire profile, so the wider the rim, the wider the tire you want to run on it.

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    Yeah, it didn't corner great. Today I got an ikon 2.35 for the front and put it at 30 psi (with tube). Will be putting an ikon 2.2 on the rear later this week. I'll see how it handles and go from there. I thought about putting a 2.2 ikon on both front and rear, too.

  29. #29
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    One other thing to consider is what are you using to get that number? If it's a gauge on a track pump, is it accurate? I have a really nice Joe Blo TURBO and I thought for sure the gauge on it must be accurate, sadly though, it turns out that it is not, it actually reads about 25-30% higher than the actual pressure, found this out after getting a Topeak Digital tyre gauge and now that's what I use to set pressures - it's no wonder I used to have such great low speed grip and trouble at higher speeds when I thought I was running 23 f/27r and in fact was runbning more like 16 f/ 21 r.

    Quote Originally Posted by clodiuspulcher View Post
    Yeah, it didn't corner great. Today I got an ikon 2.35 for the front and put it at 30 psi (with tube). Will be putting an ikon 2.2 on the rear later this week. I'll see how it handles and go from there. I thought about putting a 2.2 ikon on both front and rear, too.
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    Quote Originally Posted by LyNx View Post
    One other thing to consider is what are you using to get that number? If it's a gauge on a track pump, is it accurate? I have a really nice Joe Blo TURBO and I thought for sure the gauge on it must be accurate, sadly though, it turns out that it is not, it actually reads about 25-30% higher than the actual pressure, found this out after getting a Topeak Digital tyre gauge and now that's what I use to set pressures - it's no wonder I used to have such great low speed grip and trouble at higher speeds when I thought I was running 23 f/27r and in fact was runbning more like 16 f/ 21 r.
    Interesting. Yeah just been using the gauge on my schwinn bike pump. I also have two shock pumps I could use to check the pressure on the wheels. Maybe they are more accurate? Or at least would provide a second opinion.

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    FWIW, I run about 35-40 psi. Yeah I'm crazy, but it works for me. When I started mtbing, I had a bunch of older guys telling me to run 25 or less psi. I ran tubes back then and through a ton of pinch flats. Then I started increasing the pressure to around 30 and it was good. I went to a Santa Cruz demo and was talking with the demo guy. He was telling me about how he didn't understand why everyone was lowering the pressure in the tires and how he ran higher pressure. These demos were tubeless. Since then I have just run higher pressure. Feels faster where it counts. I try to run 30-35 psi depending on the terrain. Overall I haven't noticed that much of a difference in times because as I get fitter I get significantly faster up and down.

  32. #32
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    Quote Originally Posted by clodiuspulcher View Post
    Interesting. Yeah just been using the gauge on my schwinn bike pump. I also have two shock pumps I could use to check the pressure on the wheels. Maybe they are more accurate? Or at least would provide a second opinion.
    Neither is a good choice. You'll notice that most people are talking about pressures in 1psi increments. Fat bikers go to 0.5 or 0.25psi increments at times. Your Schwinn gauge won't be all that accurate. That pump is probably just rebadged cheap stuff anyway. The shock pumps won't be good because they're not meant to measure pressures that low. The lowest I've ever really done on any shock I've had was about 60psi. And even then, the gauge wasn't enough to give me 1psi increments. 5psi increments were about the best I could do, and that's just too vague for measuring tire pressure on a mtb. The scale/resolution of the gauge matters. Those shock pumps have gauges that will read to a couple hundred psi, and your tires are going to be at the very bottom of that. Analog gauges are most accurate in the middle of the range, and least accurate the closer you get to either extreme.

    For regular mtb tires, you're best off if the middle of your analog gauge is somewhere in the 20-50 psi range. I have a separate 30psi gauge that gets used for my fatbike tires (2-10psi) and my wife's mtb tires (probably 17-25psi). It doesn't matter which pump we use, because the pressure gets checked with a separate gauge. It doesn't get used for anything else. My commuter bike's tires will get inflated to anywhere from 45-80 psi and I use the gauge on my pump, but I inflate them with the same pump/gauge every time.

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    experiment with your bike, tires, weight and trails. you'll find what psi u like. don't take blanket statements cuz there are a lot of variables.

    for me lower psi lets me run lighter tires for the same amount of grip, however if i'm going down ALL mountain stuff, i might hit the rim. so i have to have more PSI on those trail days.

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    Quote Originally Posted by Harold View Post
    Neither is a good choice. You'll notice that most people are talking about pressures in 1psi increments. Fat bikers go to 0.5 or 0.25psi increments at times. Your Schwinn gauge won't be all that accurate. That pump is probably just rebadged cheap stuff anyway. The shock pumps won't be good because they're not meant to measure pressures that low. The lowest I've ever really done on any shock I've had was about 60psi. And even then, the gauge wasn't enough to give me 1psi increments. 5psi increments were about the best I could do, and that's just too vague for measuring tire pressure on a mtb. The scale/resolution of the gauge matters. Those shock pumps have gauges that will read to a couple hundred psi, and your tires are going to be at the very bottom of that. Analog gauges are most accurate in the middle of the range, and least accurate the closer you get to either extreme.

    For regular mtb tires, you're best off if the middle of your analog gauge is somewhere in the 20-50 psi range. I have a separate 30psi gauge that gets used for my fatbike tires (2-10psi) and my wife's mtb tires (probably 17-25psi). It doesn't matter which pump we use, because the pressure gets checked with a separate gauge. It doesn't get used for anything else. My commuter bike's tires will get inflated to anywhere from 45-80 psi and I use the gauge on my pump, but I inflate them with the same pump/gauge every time.
    Don't you spill a bit of air each time you put the nozzle on and off, thus making so you can't ever know the exact psi?

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    Quote Originally Posted by clodiuspulcher View Post
    Don't you spill a bit of air each time you put the nozzle on and off, thus making so you can't ever know the exact psi?
    No. That hiss of air is mostly not escaping the tire. That mostly comes from the pump. There are lossless air chucks, too, that cut it down even more if you care that much. Lezyne offers a lossless chuck for example.

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    i also run around 40psi on my MTB's. but considering i run about 80psi on my BMX, it feels pretty squishy...


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    GH Meiser accu-gauge just delivered.

    Just a quick check before a short spin reveals the new gauge and my cheapo digital are spot on at 21 - 25 psi but the tire thought to be at 16 front by digital and was actually 11 and another reading of 16 was 12. It appears my digital isn't accurate in the lower ranges, something I would have guessed.

    I'm on a new bike and leaving the tires as is for now, tubed 27.5 X 2.9 Sidewall indicates a range of 15 - 35 psi.
    I know for sure I want to be at least +2 over tubeless range on the low end.
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    A lot of talk about fatter tires and lower pressure lately.

    People seem to overlook that the tire giving to get better traction is a complete waste of stiffness. Although they may have better traction they lose the stiff steering and cornering so that whatever is gained in traction is lost elsewhere = Why have thru axles and try so hard to make the wheel stiffer if you deliberately let your tires flex 1/2'' either direction? Pointless.

    OP, What you likely feel with higher tire pressure is a tight, stiff precise ride. Having sharp predictable steering can be quite confidence inspiring and make the whole ride feel better.

    Nothing wrong with keeping the tires firm. The tires will give over bumps no matter what, they are rubber filled with air for that reason. I tend to like a pretty firm tire also. I don't like them solid as a rock but I certainly do not like tires that flex much either.

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    Quote Originally Posted by clodiuspulcher View Post
    Don't you spill a bit of air each time you put the nozzle on and off, thus making so you can't ever know the exact psi?


    I can check my tire psi on the car in the 35 to 37 psi range about 3 times and get the same reading on my digital gauge so at least within the .5 lbs increment no, not any meaningful loss.
    On the 4th time, I sometimes get a 1/2 lb lower reading.

    I'll check it out with bike tire ranges I run in the 16 to 30 psi. My other gauge lets me see a broad range of psi on the dial from 0 - 60 so increments of 1/2 psi or even less should be easily identified.
    Some tire chucks/gauges fit on and off so clean there is only a slight pop of the valve, no hissing.
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    Quote Originally Posted by Bigjunk1 View Post
    A lot of talk about fatter tires and lower pressure lately.
    I agree if by "lately" you mean the last 10 years or so, fatter tires combined with lower pressure seems to have been a fairly gradual evolution to me. Skinny hard tires are great on smooth surfaces but wider is much more capable (and faster!) on rough trails IME. I used to run 45psi on 1.95's back in the day because I had to in order to avoid flatting but if I tried to run anything close to that on my current 2.3's I'd be pinballing off of every rock, and not going nearly as fast.
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    Quote Originally Posted by Harold View Post
    No. That hiss of air is mostly not escaping the tire. That mostly comes from the pump. There are lossless air chucks, too, that cut it down even more if you care that much. Lezyne offers a lossless chuck for example.

    Sent from my SM-G900V using Tapatalk
    Guess I'm not doing it right then. I always lose several PSI. so I over inflate with the assumption that it will drop a few psi when I take the nozzle off.

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    I put the maxxis ikon 2.35 (exo, with tube in) on the front today and took it for a 7 mile ride. Had it the front tire in the 33-34 range. Found it a bit sluggish. I pumped it up to 40 and found it more enjoyable. Did some hard turns on a gravel part of the path and didn't wash out.

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    Quote Originally Posted by clodiuspulcher View Post
    Guess I'm not doing it right then. I always lose several PSI. so I over inflate with the assumption that it will drop a few psi when I take the nozzle off.
    If you're using a pump with a long hose to the gauge, the pressure will drop every time you put the chuck on because the air from the tire pressurizes the pump tubing before it reaches the gauge. Hence the pressure drop. Another reason that a separate gauge is useful.

    I don't think the critics of lower pressures for higher volume tires realize that deformation of a tire is directly related to the pressure and its volume. A narrower tire at a specific pressure will deform a similar amount to a larger volume tire with lower pressure. Road pressures for fatbike tires are about 15-20psi. That's very firm and will feel much like a 700x25 tire at 100psi. It's more difficult to see that when you're talking about the differences between a 2.1 and a 2.3. Especially when you consider differences in casing, which on mtb's tend to have a wider range of variability than for road tires.

    It's also not a waste of stiffness elsewhere on the bike. Some compliance is good, and some isn't. It just depends on where it is. Tire flex is one of the good ones that absorbs high frequency bumps very well. Twisting at the axle is not. And thru axles exist because of the forces disc brakes especially put on wheels, not to counter the behavior of larger tires. Flexy frames around the bb are not good. But flexy chainstays can be, depending on your preferences.

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    Just like everyone else is saying the lower the PSI the slower you can go when riding on smoother type of terrain.

    It's finding the balance between rolling resistance and added grip that can make a bike go faster. If you took 2 exact bikes with the only difference between the two being the tire pressure and raced them on paved road the bike with the higher PSI will be faster.

    Take those same two bikes and put them on a trail that has lots of rocks, roots and bumpier terrain the bike with the lower PSI may have the advantage and be faster than the bike with the higher PSI.

    If the OP weighs 175lbs and has 40PSI on 2.1 size tires it sounds like to me his trail is very smooth and hard pack (XC style) which would make him a lot quicker hence why he's having more fun. However, if he should go full speed on a more technical trail I'm almost positive he'll lose traction in a lot of areas and his confidence will diminish and force him to slow down on faster corners.

    It's all about rider weight and trail conditions that dictate what PSI you run.
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    Quote Originally Posted by clodiuspulcher View Post
    Guess I'm not doing it right then. I always lose several PSI. so I over inflate with the assumption that it will drop a few psi when I take the nozzle off.
    I pump up to .25 PSI higher than what I want to compensate for air loss upon releasing the nozzle. But if you are losing "several lbs" then you need a new pump. Or a faster release technique.
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    Quote Originally Posted by clodiuspulcher View Post
    Guess I'm not doing it right then. I always lose several PSI. so I over inflate with the assumption that it will drop a few psi when I take the nozzle off.

    Faster technique like DJ says maybe-

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    Last edited by bachman1961; 04-21-2017 at 06:34 AM.
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    tire pressure depends on

    terrain
    how fast you feel like riding that day
    how much punishment you want to take vs the tire taking some of it

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    You're not nuts....at least not obviously so Run what is most fun, but continue to experiment. You may change your mind.

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    I find I like what ever pressure that's between squirmy and feed back (bounce). This can change wit each tire.

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    As everyone has already said, we all have our preferences. Like the poster above, I find the point at which my tire starts to squirm or burp when I jump. Then I add a couple psi. I do this on all my tire/rim combos. What works for one person doesn't always work for the other. Like the OP, I also ran 2.1 tires with 40 psi when I began.
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    I vary tire pressure with the mission. On my 29er, I'll use mid-20's for a technical ride but run it up to mid-30's to ride rail trails. My 27.5+ FS only gets used in technical terrain, so I'm pretty consistent at about 18 rear/17 front (by my cheap floor pump gauge.)

    I will say that the other day I tried 21/20 on the 27.5+ and it was fine, and I set a PR on a Strava segment which was a pretty hairy downhill. Other than almost hitting a tree, I was sort of in control, so maybe the slightly higher pressures helped. Still, I will likely keep the PSI lower for ride compliance....gotta keep my old bones and joints happy.

    Reality is, the variables are too vast to determine psi on a forum. Go with what works and whatever keeps your rims from becoming intimate with rocks.

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