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  1. #1
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    Mountain Biking UK Dec2012 issue has a powertap hub test...

    of three identical weight carbon hardtails, 26"/650B/29er tired, on the same course, using the powertap to keep the power output of the rider in check as he does laps on a course. The bikes were a Felt Six Pro, Felt Nine Team, and a KHS SixFifty 609. They used water bottle ballast to get the bikes to the identical scale weights, and all ran Schwalbe Hans Damf 2.35 tires pumped to 25psi.

    The course has a 3.3km uphill followed by a 3.7km downhill for a 7km total lap. The climbs were done with the power kept to an average of 227 wats (+/- 2 watts) and the downhill with no restriction on power, just on tire grip.

    On the uphill section, the 26er scored 13:54, the 650B 13:41 and the 29er 13:39, and the downhill they were 7:58, 7:47 and 7:44 respectively. So overall the 26er was 21:52 for a lap, the 650B was 21:28, and the 29er was 21:23.
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  2. #2
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    This is very interesting. Thanks for your post. I'm surprised that the 27.5er was closer in time to the 29er that the 26er.

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  3. #3
    just some guy
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    That's cool. Next they need to perform a series of tests under different trail conditions - wide open, tight switchbacks, etc etc.

  4. #4
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    Now I am not a Dr. but I would say that is purty damn Scientific there!!!! Nice Post DeeEight!!

  5. #5
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    Good job!

    Interesting!
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  6. #6
    Killer of Chains
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    I'd be interested to see pictures of the track in question. A rocky, rooty track may give more advantage to the 29er, while a smoother, flowly trail with jumps and drops may allow the 26/27.5 to catch up.

    It'd would also be great to see the amount of movement in the steering or forces involved. I would venture to say that again, depending on the trail condition, we would see some interesting results. Likely the 26/27.5 would have lots of movement with not much effort, except in areas of rocks/roots, and the 29er would have lots of force required in technical or "jumpy" terrain.

  7. #7
    Axe
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    ..well, usually to get to the same weight one would need to have smaller tires on larger wheels. Everything else being really equal 26" should have been lighter - or with a bigger tire..

  8. #8
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    Axe the OP said they used Ballasts in the Water Bottle to even the weight..........I have been trying to download the issue on the ipad but it won't download for some damn reason....

  9. #9
    Axe
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    Quote Originally Posted by OneEyedHito View Post
    Axe the OP said they used Ballasts in the Water Bottle to even the weight..........I have been trying to download the issue on the ipad but it won't download for some damn reason....
    That was my point. They artificially increased weight on smaller sized bike. Hans Dampf on 26" is half a pound of weight less (90g per tire, 40g per rim) than on 29.
    Just pointing this out - since we are doing a "scientific" comparison and stuff.

  10. #10
    just some guy
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    Quote Originally Posted by Axe View Post
    That was my point. They artificially increased weight on smaller sized bike. Hans Dampf on 26" is half a pound of weight less (90g per tire, 40g per rim) than on 29.
    Just pointing this out - since we are doing a "scientific" comparison and stuff.
    I get it; to even out the bike weights as they did they were 'weighting', as it were, the test results towards the larger wheel sizes.

  11. #11
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    Quote Originally Posted by talabardio View Post
    I get it; to even out the bike weights as they did they were 'weighting', as it were, the test results towards the larger wheel sizes.
    No this is inaccurate.....the smaller wheels were able to retain their lighter weight per wheel which makes a bike faster than a bike with heavier wheels, irregardless of a water bottle as a ballast or a top tube that weighs more between the bikes.....the lighter 'unsprung weight' is an ADVANTAGE on climbs and descents based on their methodology....acceleration and DECELERATION are both at an advantage for a lighter wheelset which in turn for what we do on a bike makes for a faster ride.

    I finally got the issue to download and here are a couple of keys quotes that stood out to me:

    "While there was no clear winner there was a clear loser: the 26in bike was the slowest on every single lap"

    This is a pretty good article regardless of the camp each sits in......
    Attached Thumbnails Attached Thumbnails Mountain Biking UK Dec2012 issue has a powertap hub test...-650b-article-1.jpg  


  12. #12
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by Axe View Post
    That was my point. They artificially increased weight on smaller sized bike. Hans Dampf on 26" is half a pound of weight less (90g per tire, 40g per rim) than on 29.
    Just pointing this out - since we are doing a "scientific" comparison and stuff.
    Trying to "equalize" the test by making the bikes the same weight may seem like a good idea, but it is not valid for the real world. Part of the performance differences of the wheel sizes is the weight, not only in the tires, rims and spokes but the frames and forks. Nobody in a race is going to add weight to their bike because others have heavier bikes.

    Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.
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  13. #13
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    Quote Originally Posted by OneEyedHito View Post
    No this is inaccurate.....the smaller wheels were able to retain their lighter weight per wheel which makes a bike faster than a bike with heavier wheels, irregardless of a water bottle as a ballast or a top tube that weighs more between the bikes.....the lighter 'unsprung weight' is an ADVANTAGE on climbs and descents based on their methodology....acceleration and DECELERATION are both at an advantage for a lighter wheelset which in turn for what we do on a bike makes for a faster ride.

    I finally got the issue to download and here are a couple of keys quotes that stood out to me:

    "While there was no clear winner there was a clear loser: the 26in bike was the slowest on every single lap"

    This is a pretty good article regardless of the camp each sits in......
    Wheels that can accelerate and decelerate faster does not mean the bike will always be faster. There are times when a wheel that maintains its speed is faster than one the decelerates easily, and not just on the flats or downhills. It is the whole package matters.
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  14. #14
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    Quote Originally Posted by shiggy View Post
    Trying to "equalize" the test by making the bikes the same weight may seem like a good idea, but it is not valid for the real world. Part of the performance differences of the wheel sizes is the weight, not only in the tires, rims and spokes but the frames and forks. Nobody in a race is going to add weight to their bike because others have heavier bikes.

    Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.
    Agreed. The weight savings from 29er to 650b has the potential to make this "experiment" even closer.

    Then again...the 29er rider's light weight spandex get-up may equalize this equation...

  15. #15
    Axe
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    Quote Originally Posted by shiggy View Post
    Trying to "equalize" the test by making the bikes the same weight may seem like a good idea, but it is not valid for the real world. Part of the performance differences of the wheel sizes is the weight, not only in the tires, rims and spokes but the frames and forks. Nobody in a race is going to add weight to their bike because others have heavier bikes.

    Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.
    Well, they did accurately measure that a larger diameter tire has less rolling resistance and better grip.

    It does not address that you can fit more suspension with a smaller wheel, decrease weight and increase stiffness, fit smaller people etc. But all of that is difficult to test head to head.

  16. #16
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    Quote Originally Posted by Axe View Post
    Well, they did accurately measure that a larger diameter tire has less rolling resistance and better grip.

    It does not address that you can fit more suspension with a smaller wheel, decrease weight and increase stiffness, fit smaller people etc. But all of that is difficult to test head to head.
    My point is you test the wheels size/bikes for what they are and as they will be used rather than trying to make them identical in every other aspect.

    MBUK presented this as a "real world" test. The bikes should be real world, too (they were close0. The only results presented is elapsed time. The Powertap meter was used only to have the rider maintain the same pedaling effort for each test ride. They measured that the larger wheeled bikes were faster. We can only theorize that it is because of differences in RR and grip as those factors were not directly measured.

    This test was about wheel size, not suspension design, frame geometry, fit, or riding style.
    You would not do it with a 29er rigid singlespeed, 120mm travel 650B and a 26" downhill bike. That would be interesting but useless for a wheel size comparison.
    Let the "shootout" articles discuss the pros and cons of the different bike models and their intended use.

    But I MUCH prefer real world testing to isolated lab tests despite the ambiguities.

    The full lap charts, rather than just the averages, are here: Does wheel size really matter? - BikeRadar Magazines
    There is a fairly large deviation from lap to lap.
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  17. #17
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    Hmmm, interesting. Good thread. Gotta give out some rep.

  18. #18
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    I understand what they are trying to do equalizing all the bike weights which then isolates it down to just the wheel differences. It makes some sense to see it this way which is interesting but I agree with Shiggy, it's not a real world test and should be like he mentioned in post #12

    Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.
    Since the 29'er wouldn't probably change in this test (being the heaviest) the other 2 would incrementally get a little closer I assume. Maybe the 26'er would close the gap on the 650? So terrain related also. Some places the 29'er will kill the other 2 and vice versa. All I know is 650B is the Swiss Army knife of wheel sizes IMHO.
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  19. #19
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    Interesting review, but the variability is huge looking at the charts. The sample size is too small. We really need to see something like this over a 3-6 month trend.

  20. #20
    Axe
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    Quote Originally Posted by shiggy View Post
    But I MUCH prefer real world testing to isolated lab tests despite the ambiguities.
    I do like lab tests - for what they are. When they actually measure fork or frame deflection, or tire energy losses, in isolation, in a controlled environment etc. Sometimes it is quite illuminating.

    Is it mentioned there how tall the test rider is?

    ...Personally - after trying my friends 650b bike, and agreeing that it does make a lot of sense, I did not change my Nicolai to 650b. Preferred to keep 170mm on both ends, not 160mm, running a beefier tire and wheel for the same weight. Just feels more fun for this format and for my size. If I make a shorter travel, at around 140mm, lighter bike in the future, that I will setup with 650b. If I build a new hardtail or ~100mm full suspension, I would go with 29. Just my take on it.

  21. #21
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    Quote Originally Posted by Axe View Post
    I do like lab tests - for what they are. When they actually measure fork or frame deflection, or tire energy losses, in isolation, in a controlled environment etc. Sometimes it is quite illuminating.
    But potentially not completely transferable to how it performs on the trail. Tire lab tests usually run the tire on a 1-1.5 meter diameter steel drum and hold the wheel in a firm vertical position. The closest I have come to riding a bike like that is on a wind trainer.

    Any lab test needs to accurately reflect real world performance. That means conducting both types and comparing the results. Then adjusting the lab test procedures to have their results more closely match the actual performance.

    Formula 1 race teams do this all the time. Recalibrating their wind tunnels and simulators to match the results they get on the track. Each team spends tens of millions on lab testing and they still get it wrong and go in directions that do not work in the races.
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  22. #22
    Axe
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    Quote Originally Posted by shiggy View Post
    But potentially not completely transferable to how it performs on the trail. Tire lab tests usually run the tire on a 1-1.5 meter diameter steel drum and hold the wheel in a firm vertical position. The closest I have come to riding a bike like that is on a wind trainer.
    But somehow my real world experience correlates quite nicely. Tires measured low do in fact roll better..

    In some sense weighting your bike on a stand is a lab test. And on a local fireroad climb I use for training/timing - 10 extra pound on a bike pretty much mean to me I have to ride it a gear lower. But then, extra 10 deg of temperature has the same effect on me.

    One can't just use such a test, run by one particular rider, and then publish a article proclaiming a "clear loser". That seems like bollocks. At the very least they should not have artificially make the weights equal. They are not.

  23. #23
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    Quote Originally Posted by Axe View Post
    But somehow my real world experience correlates quite nicely. Tires measured low do in fact roll better..

    In some sense weighting your bike on a stand is a lab test. And on a local fireroad climb I use for training/timing - 10 extra pound on a bike pretty much mean to me I have to ride it a gear lower. But then, extra 10 deg of temperature has the same effect on me.

    One can't just use such a test, run by one particular rider, and then publish a article proclaiming a "clear loser". That seems like bollocks. At the very least they should not have artificially make the weights equal. They are not.
    Simply weighing a bike is not a performance test. Doing something to measure the effect of a given weight change is.

    MBUK's test did use a very limited data pool. I would have liked to see at least twice as many laps and thrown out the fastest and slowest lap and/or any lap with some sort of issue. If they used additional riders, each of them would have to ridden the same number of laps. I would have then used the averages of each rider for the overall results.

    But within the results of the test they did perform (the procedures of which were mostly OK) there was a "clear loser."
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  24. #24
    Axe
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    Quote Originally Posted by shiggy View Post
    Simply weighing a bike is not a performance test. Doing something to measure the effect of a given weight change is.
    I said a "test", not a "performance test". It is a clear test with very exact implications.

    Quote Originally Posted by shiggy View Post
    But within the results of the test they did perform (the procedures of which were mostly OK) there was a "clear loser."
    I think there was not, precisely for the reasons you have mentioned. "Clear loser" implies statistical significance and broad implications of the result.

  25. #25
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    Quote Originally Posted by Axe View Post
    I said a "test", not a "performance test". It is a clear test with very exact implications.

    I think there was not, precisely for the reasons you have mentioned. "Clear loser" implies statistical significance and broad implications of the result.
    Your weight "test" (a misuse of the term, as "performance test" is redundant. Weighing something is just a measurement.) is making a bigger assumption than the MBUK test. "Implication" means it have not actually been tested or proven, just suggested from other data.

    At least MBUK has actual, if incomplete, data. But within the results of the test they did perform (the procedures of which were mostly OK) there was a "clear loser," even if we find flaws in the test.

    You can not have it both ways.
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