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  1. #1
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    Which has a bigger impact?

    So I was sitting here looking at tires and reading reviews about rolling resistance of different tires. Seems as many people cannot agree on what rolls better or worse. There is the classification of XC tires roll better than DH tires, we all can agree on that. What I have noticed is some people say they have a DHR2 and it rolls great then the next review says it rolls slow. So is that a compared to what they are used to before, or does it have something to do with another factor?

    I have 4 different sets of wheels for 2 different bikes. I picked them up and gave them a spin and I noticed that the wheels I feel less tired on have the longest spin time. So the least amount of bearing drag. That got me wondering if bearing drag plays just as much of a roll as the knob height on a tire to effect rolling resistance. Then in that case, which is more important, having a great rolling wheel, or a great rolling tire? Can you run fast XC tires on slow bearings and have more rolling resistance then a trail tire on super smooth rolling bearings? Is that a factor in maintaining speed that seems to get glazed over by marketing hype of having higher P.O.E (points of engagement)?

    I would love to hear what everyones thoughts are on this. Are we all searching for that holy grail tire for the bike but overlooking the main part they spin on?

  2. #2
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    There seems to be an awful lot of variables going on with regard to determining rolling resistance. Hub drag for example... so, on the stand, relatively unweighted, one hub spins longer than another. What happens when rider weight is added to how a hub spins. A "looser" hub might spin better unweighted, but not with a rider on board. What happens when a quick spinning, poorer tolerance hub has to spin under power from the chain? My final take on RR from hub drag is that it is a non-issue when on the trail.

    Tires. I'm a bit of a tire junky and will change tires often because they are not worn out, but just because I want to try something different. Point is, I've got a lot of time on different tires. Tires do seem to play probably the biggest role in RR, __but__ it appears to be highly dependent on the trail surface. For example, on a smoother, drier track something like a 2.3 DHF 3c out back will be noticeably slower than say a Spec Ground Control 2.3, or a Nobby Nic in Pacestar. One a wet, rooty, rough, slick trail, or a loamy trail, I've found the difference in RR to be much less (not to mention loss of trail control on the "faster" tire). Speaking of the DHR2, I've got a lot of time on that tire - in 2.3 and 2.4 WT, and in DC and 3c flavors. I've found there are times it rolls fast, and other times quite slow. Overall the DC is faster, but only noticeably so on a faster, smoother type of trail. Once things get slick and chunky, the difference in RR may not be enough to warrant loss of grip with the faster rolling DC.

    IMO

  3. #3
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    ^ I'd agree with all that, good post. I will add something as simple as +/- 2-5 psi can also make a big difference.

    At 230+#'s I out roll everybody over 30 years of riding on any bike and across many sets of wheels and their corresponding bearings.
    Last edited by WHALENARD; 3 Weeks Ago at 04:24 PM.
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  4. #4
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    I'm sure there are others on here with much more experience on the subject, but my limited experience has been that high roller tires are not worth it if you lose grip, or put another way, if you need grip. The sweet spot for decent grip and rolling resistance seems to be between 2.35 to 2.50 (I have not tried 2.60 yet, that will be my next tire). I don't notice a difference in rolling resistance between a knobby 2.50 and a hybrid (high roller) 1.95. Maybe there is, if you timed it, but I don't feel a difference on pavement or dirt. Now for handling, yes, on pavement the 1.95 handles way quicker and better. But I don't feel much difference in rolling. Until a road biker blows past me on his skinny tires lol. I have a 2.8 high roller and it's noticeably slower even though it says high roller. And the grip is not quite as good as a Maxxis DHF 2.5, rolling resistance worse.

    What is the bottom line on all this? If you are doing hardpacked flowing trails, sure, try a high roller. If you need grip, or back tire climbing ability in loose dirt conditions, don't worry about rolling resistance, try a 2.5 or 2.6 with plenty of knobs, like a Maxxis tire. They seem to roll just fine to me. I always envision people talking to themselves like "I crashed bad 5 times this month, but when I didn't crash I was 2 minutes faster on my favorite 90 minute loop!" Was that 2 minutes really worth potentially ending your MTB future? In other words, don't sacrifice grip for a slightly better rolling speed. Crashes can really suck. Also a lot of people are obsessed about unsprung (wheel/tire) weight on their bikes. If adding a 1/2 pound of good, knobby, grippy front tire to your bike drastically cuts down on crashes, then that 1/2 pound is totally worth it, no matter what the weight weenies say.
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  5. #5
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    DHRs are DH tires and roll like crap. They hook up great.
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  6. #6
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    I may have my head up my ass on this but for me, 2.3 3C DHR2s can be reasonably fast to draggy as hell, depending on rim width. On Enve 24 ids, they were lightning quick, but had a death zone on the transition in corners until the bike was leaned over far enough for the side knobs to kick in. On 27 id We Are Ones, MUCH slower and draggy, but no death zone and stable and grippy AF.

    Both wheel sets had DT Swiss 240s with the standard 18 tooth star ratchet.

    And yeah - I know. How could 3 mm make that much difference? Not sure. But that is what I observed. Maybe there were other differences I am unaware of that led to the differences in feel.

  7. #7
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    Honestly for me...for tires within the same segment...I can't really tell much of a difference. I pretty much just set my tire pressure and go. I'm not a heavy rider and not super hard on tires...so I'll go with the lightest ones I can get away with...within a model range.

  8. #8
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    There are so many variables the only place to get reliable data would be in an extremely controlled environment like a lab. Soil conditions, tire pressure, rim width, rider weight, new tires/worn tires, the list goes on. Not to mention perceived experiences and personal biases throwing off the whole thing.

    Bearings are pretty cheap. Any time I need to replace one I can easily justify the extra $4 to get an ABEC 5 bearing or an Angular Contact instead of a standard bearing. IMO there is no need to jump to something like a ceramic bearing when good bearings are available at 1/8th the cost.

    Few people spend any time "maintaining" their bearings. Cartridge bearings have largely taken over and allow people to be lazy and completely neglect their stuff until it needs to be replaced for a whopping $7. Honestly I largely do that myself unless I have to address an issue.

    My question to the OP is why do you ask? Racing? Just curious?

    When it comes to tires I almost always favor grip over rolling resistance. But I should add that I'm 205 lbs and a pretty strong rider. I don't like sliding around or losing traction because I overwhelm the tires. I feel I can easily overcome the minor increase in rolling resistance of a slightly more aggressive tire. I've tried, and continue to run very low pressures for my size. Occasionally I get unlucky and will cut a tire and dent a rim, but generally I keep my pressures low in search of more grip.

    The only time I run a faster tire is for XC racing, and it's not all the time, just when I can get away with it. So for me it's good bearings and grippy tires.
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  9. #9
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    Just another variable to add to the equation. If I have a front tire that I can really trust grip wise I can always put a faster rolling tire on the back. With a given rear tire and I put a faster rolling tire on the front and don't trust it I will hate the back tire, then put a tire on the front I trust the same back tire will be perfectly fine. So-front for grip and adjust rear accordingly. The front tire I will choose for the worst conditions I might find, not for the best conditions on a given trail/area/or time of year.

  10. #10
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    I do race but in the old man slow class. So it mainly was just a hmmm I wonder moment. As I felt the different wheels vastly different without weight on them. Seeing as I do not have all the fancy watt roll down drums and all that to put a number on it I was wondering if anyone had any thought on the subject.

  11. #11
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    Most tires i dont feel them peddling but I do notice that some tires require me to peddle more, that they rob me of momentum. So a DHR will tire me out on a long ride faster than an Aggressor. The Assegai would slow me down even on the front. I was peddling on some down hill spots I normally dont. I keep my hubs well lubed and replace bearings so never have a draggy hub.

  12. #12
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    I don't race, but I keep track of times via Strava for the purpose of determining what gear (and how it's utilized - like pressures, for instance) is the fastest. I've been doing so for a long time.

    I'm 66 and ride with my 28 year old son. I want to be able to do that for as many years as I can. I don't mind if he waits on me for short periods of time on the downhills because at those speeds, waits tend to be short. But, I don't want him waiting long periods on the uphills. That's my motivation for keeping track of the data.

    For my application, tires make the biggest difference. An even bigger difference was going from 27.5 to 29, though. In that case, going from the stock 29x2.3 DHR2/DHF that seem to come on every new bike to 29x2.35 Nobby Nic Addix improved my times by 10 to 12% consistently. The impact on descents by changing tires was considerably less. Being 5% slower on a 15 minute downhill just doesn't have the impact of being 10% slower on a 2 hour climb.
    Last edited by MSU Alum; 3 Weeks Ago at 08:10 AM.

  13. #13
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    Normal loaded hub drag is way way less than mtb tire rolling resistance. Even on skinny high pressure road bike tires hub drag is still a small fraction, a few Watts compared to tens of Watts for the tire.
    Do the math.

  14. #14
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    I think there's two competing elements to it, the hysteresis losses of the tread and casing as it deforms during rolling and the losses as the tread pattern interacts with the ground.

    The first is easily measured, and I'm probably the one who you saw post that the DHRII rolls competitively on a flat surface because the Germans tested a bunch of trail tires and it did pretty good (for an aggressive tire).

    But the second is harder. For example, if there is soft ground then the tread blocks sink in and have to be pulled out, both causing losses. This would be a function of the shape, size, and height of the tread as well as the properties of the ground. That's really hard to test.

    Maybe the best strategy is to restrict your tire candidate pool to the ones that test fast on a drum, then pick from experience the one that seems to do the best on the tread interaction part for your area.

    I think I'm basically in agreement with Miker J's perspective.

  15. #15
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    Quote Originally Posted by Schulze View Post
    , the hysteresis losses of the tread and casing as it deforms during rolling
    This is by far the biggest thing for me. The best example for me was some (6 tires i got on clearance) 1000g geax tires i had with tissue paper sidewalls and a dhr-esque tread. They were super fast. Crazy fast. They folded over and blew up pretty fantastically too, so it's not surprising that tires like that don't really exist.

    My wheelset with DH DHF/DHR rolls very well on smooth surfaces when i crank the pressure up to 40psi.
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  16. #16
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    Varies with trail surface. On softer surfaces, knob height makes all the difference. On smoother, harder ones, compound does. Because I ride mostly on loose over soft(think pine straw over relatively soft dirt between the roots and rocks), a tire with lower tread rolls very fast, but also loses traction easily. So I can actually ride, particularly corner, a lot faster on slower rolling tires.
    Up to a certain point, I can literally rank how fast my tires of similar size and sidewall construction allow me to ride(corners and downhills, anyway) by weight, since it goes up the bigger the knobs get. The heavier they get, the faster I can ride them.
    How fast they roll, though, is the exact opposite.
    It's mostly constant up and down where I ride, and long climbs are rare.
    Strictly a matter of perspective(which is often lacking in these discussions), but RR tests don't do much for me, personally.

    I don't trust any of those "roll down" tests, either. You can control the results, or just screw them up, by having your weight shifted forward or back a bit with your feet and pedals in the exact same position.
    Which tire will win if I do a roll down test?
    Whichever one I want...

  17. #17
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    For a tyre that's really suited to standing climbing on a single speed, I'm really surprised (and pleased) how well Ground Control Gripton 2.3's roll.
    Much better than the pre-gripton versions, and better than Ikon's/Ardent Races.

    Not as good as the Sawtooth, but they corner better

  18. #18
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    With hubs, unless the bearings are blown up or way over pre-loaded, you’re talking about tiny differences. Particularly when loaded with a bike + person. Portions of a watt.

    With tires, you’re dealing with much larger differences.




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