1. The most important thing about buying a new bike is to make sure it fits. The only way you'll know if the bike is right for you is to size up the bike and make sure that the bike's geometry matches your body's geometry. Ask questions and do some research.
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2. If possible, try to find a shop that will let you demo the bike on real dirt. Five minutes in a parking lot won't cut it. You wouldn't buy a car without a real world test drive, and a bike should be no different.
3. Don't belive the hype. Just because your favorite rider or best friend rides a certain bike, that doesn't mean that's the best one for you. Have an open mind and be realistic about your needs and ability.
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  1. #26
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    Quote Originally Posted by DennisF View Post
    006_007, your test sounds scientific enough to me. You confirm my belief that it is unlikely that rolling resistance due to tire/tube interaction is significant or occurs at all. BUT, if you tried the same test at say 30 back /25 front PSI with tubes and 25/20 without, over some roots and other uneven trail surfaces, I would expect to see an improvment. The tire conforms to the trail surface rather than bouncing over it. There is a whitepaper by Schwalbe where they tested this, and my seat-of-the-pants experience agrees. I also believe that the tires get better traction. It is definately more comfortable!
    .
    I dunno, my experience is that less tire pressure means the tire is going to conform to irregularities on the trail more meaning more surface area contacting which equals more resistance........

    It may feel more stable and provide more traction though - but more traction is an INCREASE in resistance no?

    I give up. I am just gonna ride my damn bike

  2. #27
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    Increased traction doesn't necessarily mean increased rolling resistance. Traction stops the tire from slipping, but rolling is a different thing.

    When going over irregularities, a tire without a tube will conform to the changes more easily, so it's more noticeable than on hard and smooth surface.

    006_007, my observation could be placebo, because if the effect was as big as I perceive, it should be easily replicated in an empirical test. However, I think if you rolled as far with a tubeless setup - which is lighter and thus has less freewheeling effect - you already witnessed a lower rolling resistance. (Whether this can be noticed when riding is a different thing entirely.)

  3. #28
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    Quote Originally Posted by Saul Lumikko View Post
    Increased traction doesn't necessarily mean increased rolling resistance. Traction stops the tire from slipping, but rolling is a different thing.

    When going over irregularities, a tire without a tube will conform to the changes more easily, so it's more noticeable than on hard and smooth surface.

    006_007, my observation could be placebo, because if the effect was as big as I perceive, it should be easily replicated in an empirical test. However, I think if you rolled as far with a tubeless setup - which is lighter and thus has less freewheeling effect - you already witnessed a lower rolling resistance. (Whether this can be noticed when riding is a different thing entirely.)
    Traction and rolling resistance are different, though not exclusive. A smooth tire at 60 psi will roll better and have less perceived "resistance" than a smooth tire at 30 psi. Add in an actual tread pattern, trail surface irregularities, and fluctuations in rider weight and strange things start to happen. A softer tire will have more rolling resistance, since there is more tire material in contact with the ground. This will occur with or without tubes. You will also gain traction, as there is a larger contact patch. However, a different tread pattern may offer more traction at a given psi without impacting rolling resistance.

    Hence a difference between 2" tires and 2.3" tires

    I looked into tire mechanics a while back, and you would not believe how much science and engineering is behind upper-end tread patterns...they are not just the marketing department saying "looks cool to me"...there's work put into the design.

  4. #29
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    Karidne, I spent about $50 going tubeless. You can subtract from that $10 because otherwise I would have had to buy a spare 29" tube. The difference in how it rides is small. If it were just a matter of weight savings, even on the wheels, is it worth $50? For recreational riding, no. For racing or if you just enjoy going fast, probably. I did one race last year for bangs, enjoyed it, and plan to do three this summer. Seeing you are more into racing than I am, depending on your financial sitution, it would probably be a good thing for you. As things go, $50 isn't a huge amount of money to spend in this sport.

    That's assuming you can do it for $50 on your bike. I don't know anything about Specialized or your bike other than that they are very popular around here

    One thing, though. If you go tubeless, you don't want to have to rely on the LBS to maintain your setup. You need to know how to mount tubeless yourself. So do the conversion yourself. It isn't difficult. Getting the bead to seat enough to hold air using a hand pump is a bit of a black art at first, but not difficult after you do it once. I keep a Schrader adapter in my toolbox so I can use a compressor if I ever need to or am just lazy.

    As for new wheels, I am a relative noob, but let me share this. My old bike is a steel '98 Schwinn Mesa weighing in at around 30 lbs. I brought it at a thrift store. It still had its factory tires. I replaced them with tires from the LBS and saved 11 oz per wheel! It rode like a different bike. Pedaled easier, accelerated and stopped easier, handled better, was more responsive. A HUGE difference.

    A guy at the race had the same bike I had, a Superfly AL elite, but his had I9 wheels. He let me ride it around the start/finish area, and it was NICE. I'll bet the difference on the trail is substantial. So I plan to spend the $$$ I didn't spend on a carbon frame and get some really nice wheels sometime . You benefit from more than just weight savings, you know. A good wheelset will be stiffer and the hub will have more engagament points. Also look into thru-bolt if you don't already have thru-axle.
    Last edited by DennisF; 11-17-2012 at 05:19 AM.

  5. #30
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    It may feel more stable and provide more traction though - but more traction is an INCREASE in resistance no?
    Actually, the opposite is true, at least if we look at overall efficiency. Consider this extreme example:. You are pedaling up a hill, but the back tire is spinning and you are not moving at all. You are getting 0% efficiency. All of your energy is going into warming up the environment and tearing up the trail . You get a wider tire or let some air out of yours, and it now climbs the hill. You are no longer at 0% efficiency -- you are infinately better off! So in reality, the less slipping and sliding you do, the less work you do.

    The Schwalbe paper I mentioned a couple of posts ago claims that additional rubber on the road does not add to rolling resistance. The reason to go with narrow tires on a road bike is weight savings, but mostly lower wind resistance. It sounds like heresy based on everything I have read and been told with respect to cars, but just thinking about it logically, I see no reason why road molecules and tire molecules merely touching each other is going to generate heat.

  6. #31
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    The Schwalbe paper I mentioned a couple of posts ago claims that additional rubber on the road does not add to rolling resistance. The reason to go with narrow tires on a road bike is weight savings, but mostly lower wind resistance. It sounds like heresy based on everything I have read and been told with respect to cars, but just thinking about it logically, I see no reason why road molecules and tire molecules merely touching each other is going to generate heat.

    I know, its seems counter intuitive to think lowering tire pressure doesn't slow you down. I get the increased traction, larger contact patch, but everything I ever heard says higher pressures equal less resistance. I guess I'm just going to have to try it.

  7. #32
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    Because then you get your "cool-guy club" card.

    Ok, not really. The main purpose is flat prevention and the ability to run lower pressures w/o pinch flatting. If you are have tubeless-ready rims/tires, it will be a bit lighter than a tubed set-up. If you convert with a rim strip, it will be marginal in terms of weight reduction.
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  8. #33
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    Rolling resistance.

    It may be the wrong choice of words to choose to describe the speed in which you travel with high pressure vs low pressure. If you are on pavement or smooth, hard packed dirt, higher pressure will require less energy to cover the same distance when compared to lower pressure. If you are on a surface with a lot of bumps, lower pressure will require less energy to cover the same distance compared to higher pressure.

    Think of it this way. The shortest distance between two points is a straight line. A straight line is the most efficient path between two points.

    Now, picture a bike from a side view and imagine a chart of the Axels' paths while riding a smooth road at 60 psi. In that scenario, higher pressure or lower pressure results in a straight line. Now, imagine putting a bunch of roots and rocks along that path and chart your axles' paths with 60 psi and also 25 psi. the 60 psi path will look like a heart beat monitor and the low pressure will look like a sound wave. Every time you change your axles' paths abruptly, you are loosing energy/efficiency.

    If you have 100% energy devoted to moving the bicycle forward, any movement in any direction other than forward reduces your energy devoted to moving forward and converts it to energy in a different direction. It's the same reason we use suspension. It's all about energy efficiency.

    There is a point of diminishing returns. It's all about trade-offs. That's why no one answer is best in every situation.
    No, YOU don't understand. You're making an ass of yourself for all of eternity.

  9. #34
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    I have a dolly that i use to move stuff with. Usually, with the tires aired up, i strap something on it and push it along. Not much effort. The other day, the tires were lower than normal and squished about 1/4-1/2 its total sidewall height with the same thing on it. It took a bit of effort to roll this around. I doubt it was due to the added tread on the pavement. Probably more the "flattening" of the contact point. But, lower pressure does add to rolling resistance.

    I'm sure that low pressures (big reason to go tubeless) has its traction benefits. But, there must be a rolling resistance added by doing it. Is this resistance noticed on a rocky trail while ascending or descending? I don't know. Does the resistance outweigh the traction benefits? Everyone has to make that decision for themselves.

  10. #35
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    Quote Originally Posted by jetboy23 View Post
    I have a dolly that i use to move stuff with. Usually, with the tires aired up, i strap something on it and push it along. Not much effort. The other day, the tires were lower than normal and squished about 1/4-1/2 its total sidewall height with the same thing on it. It took a bit of effort to roll this around. I doubt it was due to the added tread on the pavement. Probably more the "flattening" of the contact point. But, lower pressure does add to rolling resistance.

    I'm sure that low pressures (big reason to go tubeless) has its traction benefits. But, there must be a rolling resistance added by doing it. Is this resistance noticed on a rocky trail while ascending or descending? I don't know. Does the resistance outweigh the traction benefits? Everyone has to make that decision for themselves.
    This is not accurate for bicycle tires. Do not assume that lower air pressure results in higher rolling resistance. That is ancient thinking. Roadies used to believe that a tire with 120 psi would have less rolling resistance than a tire at 100 psi. This has been proven to be wrong.

    Lower pressure does not add to rolling resistance.

  11. #36
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    I went tubeless because i kept geting flats.

  12. #37
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    A roadie (135lb lightweight) on rock hard tires at 120psi or rock hard tires at 100psi? Neither are going to deform (flatten) the contact patch with pressures that high with so little volume. Air up that road tire to 50psi and there will be a difference in rolling resistance. If there wasn't, they would only use 50psi. Mountain bike tires have much more volume and are used at much lower pressure. A "flatter" tire is going to roll slower. Mountain bike, car, trailer, dolly, hula hoop, and even a roadie tire. I can feel the difference with my legs between a 45psi tire and a 30psi tire.

  13. #38
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    Quote Originally Posted by DavyRay View Post
    This is not accurate for bicycle tires. Do not assume that lower air pressure results in higher rolling resistance. That is ancient thinking. Roadies used to believe that a tire with 120 psi would have less rolling resistance than a tire at 100 psi. This has been proven to be wrong.

    Lower pressure does not add to rolling resistance.
    On a road bike, you gain some speed by this small drop in pressure because the bike is not bouncing "over" every single surface irregularity, much like how a suspended bike is faster over rough terrain that a fully stiff frame.

    On a mountain bike, a drop in air pressure after a certain point will increase your rolling resistance, and the amount of work required to move the bike a certain distance. The key is finding a tire's "butter zone", or the point at which the tire is most efficient in passing over the majority of surface irregularities (like the average size of gravel on a trail). The trail type matters, too (DH rock garden vs. flowing singletrack).

    However, there are exceptions. As I found out from experience and a following thread post on this website, a tire with tall, knobby tread, when inflated to a high psi, will squirm around more than at a lower psi, and therefore have more rolling resistance at high psi's than at lower psi's (I had WTB mutanoraptors inflated to 45-50 psi while riding on wet concrete...almost killed me). Squirming is a loss in tire efficiency.

    Jetboy's on the right track with this...though again, you do gain some speed in not bumping over every grain of sand (drop from 120 to 100 gives you this little bit of cushion).

    Again, finding the "butter zone" for a specific tire is key.

  14. #39
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    Quote Originally Posted by CSC View Post
    On a road bike, you gain some speed by this small drop in pressure because the bike is not bouncing "over" every single surface irregularity, much like how a suspended bike is faster over rough terrain that a fully stiff frame.

    On a mountain bike, a drop in air pressure after a certain point will increase your rolling resistance, and the amount of work required to move the bike a certain distance. The key is finding a tire's "butter zone", or the point at which the tire is most efficient in passing over the majority of surface irregularities (like the average size of gravel on a trail). The trail type matters, too (DH rock garden vs. flowing singletrack).

    However, there are exceptions. As I found out from experience and a following thread post on this website, a tire with tall, knobby tread, when inflated to a high psi, will squirm around more than at a lower psi, and therefore have more rolling resistance at high psi's than at lower psi's (I had WTB mutanoraptors inflated to 45-50 psi while riding on wet concrete...almost killed me). Squirming is a loss in tire efficiency.

    Jetboy's on the right track with this...though again, you do gain some speed in not bumping over every grain of sand (drop from 120 to 100 gives you this little bit of cushion).

    Again, finding the "butter zone" for a specific tire is key.
    Good. The fallacy is that some people believe that higher pressures always result in less rolling resistance. The actual results are what matter. Tire width plays a part in this. A 20mm wide tire at very high pressure has to deform the same amount as a 25mm tire at lower pressure. The shape of the contact patch is different. The 20mm casing has to deform over a longer distance to support the riders weight, so it has a larger deflection amount than the 25mm wide tire.

    Riding on rock-hard tires feels efficient, but that is just a feeling.

  15. #40
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    Here's an interesting read: Tech FAQ: Again, bigger tires roll faster!
    No, YOU don't understand. You're making an ass of yourself for all of eternity.

  16. #41
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    They told me bathing in boiling water would be fatal, so I dropped the temperature below zero and it froze. I still didn't get the bath.

    That's what I think when I read stuff about lower pressures increasing rolling resistance. Well of course the rolling resistance will be higher, if you're riding flattened 2.35 mm mud tires on smooth pavement. What happens on the trail is vastly different.

  17. #42
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    Quote Originally Posted by Saul Lumikko View Post
    They told me bathing in boiling water would be fatal, so I dropped the temperature below zero and it froze. I still didn't get the bath.

    That's what I think when I read stuff about lower pressures increasing rolling resistance. Well of course the rolling resistance will be higher, if you're riding flattened 2.35 mm mud tires on smooth pavement. What happens on the trail is vastly different.
    A flat tire on or off road does increase rolling resistance. I guarantee it.

    A flattened mud tire may be faster at getting through mud than a pumped up tire, but it still has more rolling resistance than when inflated to its "Goldilocks" psi.

    And what does any of this have to do with tubed vs tubeless, anyway?

  18. #43
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    Quote Originally Posted by CSC View Post
    A flat tire on or off road does increase rolling resistance. I guarantee it.

    A flattened mud tire may be faster at getting through mud than a pumped up tire, but it still has more rolling resistance than when inflated to its "Goldilocks" psi.

    And what does any of this have to do with tubed vs tubeless, anyway?
    Thank you.. ... I do like Butter zone though

  19. #44
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    Quote Originally Posted by wmac View Post
    Here's an interesting read: Tech FAQ: Again, bigger tires roll faster!


    The comments section of that article is better then the article itself. Good reading nonetheless. Thanks.

  20. #45
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    CSC, you are right. Rolling resistance is rolling resistance. The terrain doesn't magically change the rolling resistance physics. Running lower pressure is higher rolling resistance regardless of the terrain. The same bike with the same rider with the same tires is going to have lower rolling resistance at 40 psi vs 25 psi regardless of terrain. The difference is the energy expended to make it from point a to point b on various terrain with 40 psi vs 25 psi. Running lower tire pressures is an argument of efficiency, not rolling resistance. The reason this is relevant is because you can run lower pressures, when necessary, with a tubeless setup compared to a tubed set up. Running lower pressures is not more efficient on every trail.
    No, YOU don't understand. You're making an ass of yourself for all of eternity.

  21. #46
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    So how low can one safely run with tubed slimed tires?

  22. #47
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    Quote Originally Posted by Z4good View Post
    So how low can one safely run with tubed slimed tires?
    You could in theory run them flat (no air...) on a smooth surface...assuming you did not cut the wall of the tube with your rim or something on the ground.

    In practice, you would have to have enough air to press and hold the tire bead to the rim...in the neighborhood of 15-20 psi, to be safe. I have ridden on less than 20 psi...not great, but possible. Tubeless allows you to glue the bead to the rim, so you might get lower psi on the tubeless set-up, but things would start getting sketchy.

    EDIT: I mean, no one would run 15 psi tubeless, right?

    The whole issue is how low can you go and not have the tire pop off the rim or compress and get lacerated by the rim? Tubeless gives you a bit more flexibility.

  23. #48
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    Quote Originally Posted by KAriadne View Post
    Let me add my question to this thread:

    I'm looking for ways to make my bike lighter, will going tubeless help?

    Some details, if you want them:

    I've been riding this bike (2011 Stumpjumper Comp 29) for 1 1/2 seasons. Other than putting some nifty grips on it and some knobbier tires, it's all as it came from the from the factory.

    This year was my first season of racing (Sport class). I weigh 125 lbs. I've never had a pinch flat. I have had 2 punctures this year (same trail, different days). I usually run 24-26 psi. A certain trail is easier at 22-23 psi. Often, I just squeeze my tires, decide "good enough," and go ride. I like The Captain Control tires.

    Husband does most of my bike maintenance (but the local shop does stuff that needs a tool he doesn't have and things he doesn't have time to do). He expects me to do more and more of my own bike work. That would include going tubeless since he has no interest in fussing with it.

    I already know I'm converting from 3 X 10 to 1 X 10. I'm looking for other ways to lighten the bike. Right now it is 25 lbs. Guy at the shop is recommending new wheels.
    Check your rims first. My 2012 SJ FSR Comp 29 came taped stock so all I had to do was buy valves and sealant.
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  24. #49
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    Quote Originally Posted by Z4good View Post
    So how low can one safely run with tubed slimed tires?
    Depends on your weight, riding style, terrain type, tube type and tire type. I experiment and run different psi on different trails in different conditions.

    On pavement or hard packed, smooth, single track, I run max psi according to sidewall. A lot of people recommend running as low psi as possible. Not sure I recommend that for every trail unless your goal is to have the most traction and the most comfortable ride possible. You can find out your minimum PSI by going to the roughest section of the trail and doing multiple passes and lowering the pressure by 2 psi each pass until you can feel your rim very lightly "kiss" a rock/root. If there are any rocky downhill sections, use that as your experimentation run. If you don't pinch flat, raise the psi by 1 and that should be your minimum.
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  25. #50
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    I can't believe all the back and forth about rolling resistance and the theory of it. Stop reading this crap, convert them to tubeless, run lower pressure than your are used to, and go for a ride. Then you can make your own opinion of whether or not you think it works. This reminds of me of all the theorizing that goes on about 29ers, whether they roll over things easier, whether they climb easier, whether they are faster, blah blah blah. Just buy one and ride it. If you like it, great, if you don't, sell it and go back to your 26er.
    Geologist by trade...bicycle mechanic (former) by the grace of God!

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