26" vs 29" Long Report- Mtbr.com
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  1. #1
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    26" vs 29" Long Report

    This is from www.cyclingnews.com



    Dave Harris' 26 vs. 29 inch challenge
    By Steve Medcroft

    Dave Harris contemplates the 26in vs 29in conundrum
    Photo: © teamhealthfx.com
    Twenty six or twenty nine inch wheels - which is the better format for cross country mountain biking? Endurance racer Dave Harris (Team HealthFX) decided to settle the question for himself by putting two of his own bikes to the test at the 24 Hours in the Old Pueblo (February 18 and 19, 2006). Armed with a Trek Top Fuel and a Salsa Dos Niner, Harris used a Power Tap integrated hub system to gather data about his performance on the mostly rolling desert course in Oracle, Arizona (about thirty miles Northwest of Tucson).

    He got the idea to do the comparisons two years ago. "I'm a competitive racer and I take it seriously," he says. "Once I turned to racing endurance events, you can't help but notice the popularity of two-niner bikes; the Fisher team (Nat Ross and Cameron Chambers) do really well with them. I got intrigued. I looked around for some research to see if the claims I heard about their performance was true but all I found was an abstract from a study which provides no information about the conditions under which the study was performed and ravings on two-niner forums. But it's like going to the Catholic Church and asking if God exists so I bought two last year to figure it out for myself."

    Harris says that after several months of riding he worried that he wasn't gaining in performance. "As an engineer [Harris works for a Virginia-based engineering consulting firm], I needed objective evidence to support what I was feeling" Which was? "I just didn't feel that my two-niners were as fast as my Fuel. They're more fun to ride but I was getting the sense that I was going slower." Which was a paradox. "Since that went against everything everyone said, I knew I couldn't just trust my perception. Since I've been training by power for a long time, I set up a 29in inch wheel with a Power Tap hub and decided to test my bikes side by side."

    Harris says that although his was not a fully-funded scientific test, he took the experiment seriously enough to set the bikes up in similar ways. "Both bikes weigh 25.5 pounds," he says. "They both have Specialized Fast Trak tires." Because a two-niner wheel has a ten percent larger circumference than a two-sixer and front and rear cogset combinations would have produced different gear-inch measurements, Harris even tried to normalize the drivetrains. "I put a smaller middle ring on the Dos Niner."

    The 24 hours in the Old Pueblo wasn't the first time Harris had done side-by-side comparisons of power measurements from his two bikes. In the first test - on a relatively smooth forest service road (a constant climb) in January - he gave the Fuel a slight edge. In early February, on a 3.2-mile competitive mountain bike loop at McDowell Mountain park in Fountain Hills, Arizona, he declared the competition a tie After careful analysis of some minor differences in the power meter readings between the two bikes (recorded five days apart) after the second test, he chalked up the better readings from the Fuel as his just 'feeling' better during the Fuel test run. Old Pueblo, with its constant conditions and multiple laps of data to analyze, seemed like a better laboratory for his experiment.

    The day after he finished the Arizona 24-hour epic, Harris sat down with the power data from his daytime race laps (although he traded the lead with ultimate winner Tinker Juarez into the night, vision problems caused Harris to sit out the early morning hours so he dismissed night laps from the test) and created some scenarios on his computer.

    "There were a lot of different ways to look at the data," Harris said about how he broke down the results. "But people have enough difficulty understanding power in general so I kept it simple and looked at lap time versus average power." Simply put, he wanted to kow how much power was required to drive each bike around the course and if there was a difference between the bikes.

    Based on that data, Harris concluded that his Salsa required more average power to achieve the same lap times over the same terrain in the same conditions as his Trek (175 watts for the Fuel, 188 for the Dos Niner). He says that by his measure, if he rode both bikes at the same power output (presumably a limitation of his physique and fitness), Harris calculates that his two-niner lap times would be about two minutes slower. "I think I can attribute some of the difference to the power required to accelerate each bike," he says. But adds, "I can only base this on impressions. And my impression, my sensation, is that Dos Niner does not accelerate as fast as the Fuel."

    Harris says he realizes that his test was about his performance on his bikes and not in indictment of the two-niner format. "I haven't tested the bikes on descents and technical, rocky terrain," he adds. "I think that if I do, the Dos Niner will shine on rocky terrain." But for now, the experiement at the 24 Hours of Old Pueblo has him wondering if anyone's looking to buy a Salsa Dos Niner with a Power Tap hub.

    Forty year old Dave Harris is an ultra-endurance mountian-bike racer based in Durango, Colorado. He won the West-coast based Endurance 100 endurance series last year and plans to mount a serious challenge for the Trans-Rockies co-ed title with teammate Lynda Wallenfels. He writes a blog on his team's Web site at teamhealthfx.com.

  2. #2
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    Questioning!

    Now I need something at least as good to tell me 29" wheels are faster. I luv'em, no doubt. but 2 min. per lap? Give me some objective data and I'll be grateful. But this stuff is pretty good.


    Let's see, in the trans-iowa if it takes 30 hours and you can save 2 min. per hour then the 26 wheel could give you ONE HOUR by the finish. See? Now that I've sold off all of my 26" stuff....

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    I could be wrong but isn't that course pretty much connected service/county/BLM/pavement? Little to no sudden stops, turns, quick accelerations, etc. If this is the case I'd be running a super lightweight cyclocross setup with some fattie Tufo's.

    Look at the records on the GDR...the most recent on 29"ers.

    If I were that heavy into racing (read sponsored and had multiple bikes and a large budget with a full time paid mechanic) I'd have an arsenal of rides. For instance, the Winter Park MTB series. I'd do that on a 26"er (20 miles about max for the Expert races) - but on the longer endurance stuff where you are riding long doubletrack for hours on hours and don't have the sudden ups, downs, etc. I'd ride the 29"er probably all the time for the long stuff.
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    Quote Originally Posted by ftp13
    "They're more fun to ride but I was getting the sense that I was going slower."
    Hmm... I think he's onto something here. Maybe wheel size doesn't matter after all, and we ought to all just slow down!

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    it seems to me that a test like that should be done on two more simillar bikes like two rigid singlespeeds with similar gear inches. I think that the technology that is put into the trek is a bit of an advantage. What kind of wheels were used in the testing? What kind of suspension did the trek have? If we had a pure bred carbon fiber FS race bike in 29" format I wonder how would the times compare? I appreciate the objectivity done in this study but I would like to see some kind of tests that could be done under stricter guidlines.
    what the fu#k is the internet?

  7. #7
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    whoa. that dude is a freak! cool that he did that, but there are some obvious issues...

    i wonder how consistent of power he needs, even staying on the same bike, for each lap.

    also, i always thought that power was only one part. if you use the brakes less on a DH, you go faster. power is all important only if you are pedalling all the time, like in a TT or something.

    isn't it lap times that are important? he never mentioned that.

    those bikes are sort of different, too. wonder what the pwer numbers are for a bunch of different 26ers...

    does the powertap work on all size kegs? isn't watts a sketchy part of LA?

    that dude's camp must have been quite the party between laps! good to see people out there enjoying themselves.
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    Quote Originally Posted by 2melow
    I could be wrong but isn't that course pretty much connected service/county/BLM/pavement? Little to no sudden stops, turns, quick accelerations, etc.
    Okay.

    You're wrong.

    There is zero pavement, some fire roads, and alot of very twisty singletrack thru the cacti. So twisty in fact, that one needs to accelarate out of tons of corners that are quite tight and loose.

  9. #9
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    If the course is the same for both bikes, which makes it a fair test, then it takes the same amount of energy no matter what wheel he is riding. Right?

    A perfect situation to compare the bikes would be the same course for both. Then lap times would be all that is needed to tell the difference.

    Why did he need to do that powertap hub thing and change gears and what not? Just freaking ride the bikes and look at your time. It is not scientific, but it is simple.

    Is there a 29" version of the Specialized Fast Track tire? Is that the one time deal where they had a few hundred Specialized 29er tires left over?

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    Quote Originally Posted by Quasi
    If the course is the same for both bikes, which makes it a fair test, then it takes the same amount of energy no matter what wheel he is riding. Right?

    A perfect situation to compare the bikes would be the same course for both. Then lap times would be all that is needed to tell the difference.

    Why did he need to do that powertap hub thing and change gears and what not? Just freaking ride the bikes and look at your time. It is not scientific, but it is simple.

    Is there a 29" version of the Specialized Fast Track tire? Is that the one time deal where they had a few hundred Specialized 29er tires left over?
    Nope, too many variables between laps. lap times will always flucuate depending on how you feel. Power output however is quantifiable, if lap times were virtually identical yet one bike required more power to do that lap you have taken the rider out of the equation.
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    Quote Originally Posted by Quasi
    ...Is there a 29" version of the Specialized Fast Track tire? Is that the one time deal where they had a few hundred Specialized 29er tires left over?
    Where have you been? Yes there is and no it is not.
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    Agreed. Even with the same bike there were a couple sets of laps at about the same power level and a 1-2 minute time difference.
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    standards

    I could be mistaken, but I don't remember anybody making this big of an issue over efficiency and speed when full suspension XC bikes were introduced. As I recall, it was always sort of accepted that, "yeah, they're going to weigh a bit more, and yeah, they might not be as snappy off the start, but overall you'll appreciate the comfort and control and their ability to swallow the bumps." I don't see how 29ers are any different, really. But the 29er contingency is either choosing to, or being asked to, take the position that their bikes have no shortcomings, yet they provide all these benefits! Hell, that's the Holy Grail of bike design -- is it really fair to expect the 29er to deliver everything? Is it at all reasonable to assert that it does? Personally, I choose to accept these six propositions and be done with it:

    1) A 3-inch-larger wheel diameter will make a significant improvement in ride quality and momentum, but probably not a miraculous improvement.

    2) A 3-inch-smaller wheel diameter will have some drawbacks, but they probably aren't devastating drawbacks.

    3) Bigger wheels maintain momentum and roll over things better.

    4) Smaller wheels are easier to spin and to turn.

    5) A 29er is a really good idea for tall people, and is a pretty darn good idea for a bunch of other people, but it might not be for everybody.

    6) The 26er has served its purpose well for 30 years, and will continue to be a viable and sensible option for many riders, but not all riders.

    It just doesn't seem that hard for me to acknowledge their weaknesses while I enjoy their strengths. I mean, they're different bikes, right? They're going to be different! I completely fail to see why anyone even has to take sides on this.
    Last edited by Joe Sausagehead; 03-03-2006 at 11:35 PM.

  14. #14
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    Quote Originally Posted by Joe Sausagehead
    I could be mistaken, but I don't recall anybody making this big of an issue over efficiency and speed when full suspension XC bikes were introduced. As I recall, it was always sort of accepted that, "yeah, they're going to weigh a bit more, and yeah, they might not be as snappy off the start, but overall you'll appreciate the comfort and control and their ability to swallow the bumps." I don't see how 29ers are any different, really. But the 29er contingency is either choosing to or being asked to take the position that their bikes have no shortcomings, yet they provide all these benefits! Hell, that's the Holy Grail of bike design -- is it really fair to expect the 29er to deliver everything? Is it at all reasonable to assert that it does? Personally, I choose to accept these six propositions and be done with it:

    1) A 3-inch-larger wheel diameter will make a significant improvement in ride quality and momentum, but probably not a miraculous improvement.

    2) A 3-inch-smaller wheel diameter will have some drawbacks, but they probably aren't devastating drawbacks.

    3) Bigger wheels maintain momentum and roll over things better.

    4) Smaller wheels are easier to spin and to turn.

    5) A 29er is a really good idea for tall people, and is a pretty darn good idea for a bunch of other people, but it might not be for everybody.

    6) The 26er has served its purpose well for 30 years, and will continue to be a viable and sensible option for a lot of riders.

    It just doesn't seem that hard for me to acknowledge the weaknesses while I enjoy the strengths. I mean, they're different bikes, right? They're going to be different! I completely fail to see why anyone even has to take sides on this.
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    Taking sides

    Quote Originally Posted by Joe Sausagehead
    I completely fail to see why anyone even has to take sides on this.
    If you could save 2 minutes per hour of racing with the same power output, that would be HUGE! I dig the big wheels, really feel good on'em, but 2 minutes per hour is HUGE! I don't wanna look like a gorilla on a tricycle anymore but 2 minutes is HUGE! Is it true? I don't know for sure but if it is, it's HUGE!

    On the other hand, if 2 minutes per hour doesn't matter, then it just doesn't matter.

    Heh, maybe a guy should train on his 29 and race his 26

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    2 minutes per hour, I've finished mid-pack dozens of times with such time on the winner. I onder how much a world class athlete would lose on a department store bike rather than his super trick racing machine. Probably about the same :-)

  17. #17
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    nothing has been proved...

    Quote Originally Posted by Fastskiguy
    If you could save 2 minutes per hour of racing with the same power output, that would be HUGE! I dig the big wheels, really feel good on'em, but 2 minutes per hour is HUGE! I don't wanna look like a gorilla on a tricycle anymore but 2 minutes is HUGE! Is it true? I don't know for sure but if it is, it's HUGE!

    On the other hand, if 2 minutes per hour doesn't matter, then it just doesn't matter.

    Heh, maybe a guy should train on his 29 and race his 26
    I think that it's foolish to make any conclusions based on this "study". Dave Harris is clearly a very competent bicycle rider and probably a damned fine coach and sports fitness technology user. But he hasn't designed a study to describe the difference across a broad range of terrain, rider size, bicycle type, tire pressure, etc. Nor has he controlled all the causal factors that could be affecting his outcome. Nor has he subjected his work to peer review. Etc. Etc.

    Here's what he said about the data he produced and based conclusions on (from this thread):

    Quote Originally Posted by hairball_dh
    Thanks for the lesson, but I'm not a new scientist. My question is simple: which bike is faster for me, my Dos or my Fuel? Add to that question the constraints of differing types of terrain. Note I said *my* bikes, and for *me*. I have no time, funding, or even inclination to do such studies for the masses. I want to know what is faster for me, and where.
    He's really pretty much hostile to critism. That ain't science, that's a guy with a couple powertaps going out and looking at what data they give him, writing it up to look like science, then some idiot sports journalist reporting on it as science.

    Now, are his findings complete bunk? I dunno. I think that on certain terrain, a good consistent pebbly surface for example, the little-wheel bike might very well more efficient. And I think maybe that on a really tough technical course, the bigwheel might be.

    Not meaning to be insulting. I don't think this fellow is dumb, and I think he did a fine job of testing his own curiosity in a situation that was important to him. But it's wrong to pass it off as science. And it's always wrong for a journalist to elevate junk science and help pass it off as real science.
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    Energy Storage

    Mr. Harris does not give a full bike build list, but we can rather safely presume that his complete 29er wheelset (with tires) is heavier at the rim. If that is so, then at any given ground speed there is more energy stored in his 29er wheels- and that is energy the rider must supply every time he accelerates the bicycle. It would explain the discrepancy in required power he measured. It is NOT the same as simple rolling resistance, where the bigger wheel still rules. Once up to speed, your 29er requires less energy to keep it there than its 26" equivalent. So which of those two factors predominates depends on the course, in some places they will just cancel each other out entirely. Really though, Harris' experiment is not so surprising, he appears to be simply confirming long-known velo-physics that a heavier bicycle wheel accelerates slower (i.e. requires more energy) than a heavier one. He is also fair enough to comment on where the bigger wheels should have an advantage though he didn't test there.

    What I'm taking home from this is weight at the rim is still very important to overall performance- same as it ever was! That, and remember to use the 29er's added cornering grip and better balance to carry a little more speed through turns. Slow down less, accelerate less.

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    I think it's more important how you handle wheel weight. Can't handle it, light is what you need.
    I bet really heavy wheels can be built (of just weight added) and two equally strong riders all at once start lapping very differently.
    Really, the 29 vs 26 weight increase IMO is hardly worth discussion about, a factor so small it's effect cannot be measured in the wild. In an XC race situation, if you apply yor usual out-of-corner sprinting power to just the 300-350g of added weight in dragless wheel form, after a couple seconds you have it past safe tafe-off/landing speeds for airliners. 10s to Mach 1?
    See what happens of you apply the same sprinting power to a yourself+bike a couple seconds, you barely hit jogging speeds :-) That's how minute the wheelweight difference is. If you go from 26" folding to wire tires, you're often there already.

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    C'mon Now

    I totally agree there are guys who can push heavier wheels- stronger riders, of course. Now give that stronger rider a lighter wheelset- he will accelerate faster, every time. The same thing happens with a motorcycle, a car, whatever. Same power + lighter wheels = faster acceleration. Physical laws apply that go beyond "I think", "I bet", "IMHO".

    Harris himself acknowledged that there are places where the 29er wheels would be advantageous, so maybe we can admit that a lighter wheel is quicker to accelerate. It is after all the truth. Let's not hurt our own credibility.

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    I meant, one will be able to get the most from the heavy wheels in preserving momentum and such, they other will just have the added weight bothering him everywhere.
    If you take every corner the same on both 26" and 29" bikes, one bike is being used improperly.
    With equal power at my disposal, I wouldn't know how to get around a lap as fast on a 26" bike as with 29". I could when I just had my first 29" bike, but now that I have found the required 29" riding style for my case, no looking back. And I get to cruise so often when in a agroup with 26" riders. Get to brake a lot on descends too. Really I need to be riding on my own to not feel held back. On climbs and straight, obviously, only my fitness is a real factor, and I suck there.

  22. #22
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    I agree here.

    Quote Originally Posted by Cloxxki
    I meant, one will be able to get the most from the heavy wheels in preserving momentum and such, they other will just have the added weight bothering him everywhere.
    If you take every corner the same on both 26" and 29" bikes, one bike is being used improperly.
    With equal power at my disposal, I wouldn't know how to get around a lap as fast on a 26" bike as with 29". I could when I just had my first 29" bike, but now that I have found the required 29" riding style for my case, no looking back. And I get to cruise so often when in a agroup with 26" riders. Get to brake a lot on descends too. Really I need to be riding on my own to not feel held back. On climbs and straight, obviously, only my fitness is a real factor, and I suck there.
    There is a different skill set required to get the most out of a 29"er. Just like any other category of bike. You need to be able to apply the skill, and the power to get the fastest lap times. Power meters do not measure such data.
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    If you have 2 riders of similar weight, they could follow each around a lap, but keeping a bit of distance so they can apply their own riding style to the fullest, while still setting an identical pace and lap time. Even if they are the same weight and set the same time, likely they won't use the same everage power. Especially the guy riding behind might have an edge to ride economically. Cruise longer, corner harder, accelerate less, pick smart lines, etc. If they take turns at this, while keeping pace very similar, interesting data will be gathered.
    After riding both bikes, most likely one rider or rider/bike combo will turn out to be the most efficient around the track, while weight was not a factor. Identical twins or team mates are the best test subjects, as no-one else can be paid enough to wear matching outfits that minimize air drag differences.

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    I wonder why the results on the Fuel vary so much.

    He had a group of four laps (4, 11, 12, 13) with times between ~65min (12) and ~67:30 (11) and power from ~182 (13) to ~192 (4).

    The lap with the highest power output is third fastest (4).
    The lap at the lowest power is second fastest (13).

    Why was the Fuel 2 minutes faster on lap 12 at slightly less power than it was on lap 4 (3% faster, 0.5% less power)?
    Why was it 30 seconds faster (0.75%) on lap 13 with ~5% less power than it was on lap 4?

    The power and time difference between lap 12 (fastest) and lap 11 (slowest) are both ~3.7%
    All said, the results are hardly conclusive. Too many other variables. The only thing that is certain is both of his laps on the Dos were slower than most of the Fuel laps.
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    I view this as an apples and oranges situation. The Dos Niner is a soft tail. The Trek Top Fuel is a full suspension bike. There are other factors at work here other than simply wheel size. There's too many variables. The study is meaningless.

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    Horses & Courses

    While riding today, the mind began wondering: just what sort of trail or course would most hobble a typical 29er? I think it's a tight venue where you're always either accelerating or braking hard on a smooth surface with traction not limiting, and where turns are configured to minimize the carrying of corner speed. Basically, a place where none of the usual 29er advantages come into play and the upper hand simply goes to machines with less rotating weight to start and stop, the 26" bike. You could actually make a rudimentary form of this course in a parking lot just for kicks! Even better, then use stick-on wheel balancing weights to make the 26" wheels heavier and repeat the contest- the 29er should now win. Shock! Horror! Or how 'bout mtb drag races? I'll bet the 26 nails every holeshot, with the 29er owning trap speed honors.

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    Quote Originally Posted by Maxrep
    I would echo TomP's thoughts.

    PowerTaps, really folks, they are just toys. One powertap is only comparable against itself, with its own margin of error based on its accuracy, or lack there of. Trying to compare TWO separate units is just wishful thinking. I have owned three $1600 Kettler ergo racers and a $6000 Velotron. Their own wattage measurements will always vary from unit to unit. So, if you think a powertap hub, bouncing around on a mountain bike, is more than a training toy, you are mistaken.

    I get the feeling that Harris would have found the 26 inch bike faster riding a straight cobblestone road!

    With the extra grip afforded by the 29 inch tire, a racer also has the luxury of moving to a tire style that has a lower rolling resistance than what might be chosen if he was racing on a 26 inch tire.

    It;s pretty funny that you go on about the inaccuracies of a power measuring device( +/- 1.5% by the way) which has actual quantifiable data but then talk about complete specualtive things like tire style and rolling resistance like they are fact. You do the congregation...er forum proud.
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    Questions

    First off Dave is a fine racer. When his test first came up on this board a month ago I read his web page and had some questions. Ever jump on your favorite bike and just go faster? I'm not familiar with a Power Tap but wouldn't the Stomp Test be affected by chain lenght? Would the full suspension soak up some of the power in the Stomp and give a lower reading? All in all I really don't need the numbers to tell me which I like better but I wonder, if the numbers say A is faster Than B If you believe the formula is correct you can ride A (More Spirited) and make it that way. I will wait until Niner releases the new FS and do my own test 29ST vs.29FS. Won't be using a 26 cause my body already told me which I like better.

  29. #29
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    But..

    If the 29er moves 10" further on one revolution of the crankset how can it be as much as 2 min slower when it carrys better momentum with 10% taller gearing?

    PS; please explain the above as if im 3, thats 3 beers in...

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    Quote Originally Posted by jrm
    If the 29er moves 10" further on one revolution of the crankset how can it be as much as 2 min slower when it carrys better momentum with 10% taller gearing?

    PS; please explain the above as if im 3, thats 3 beers in...
    If the gearing (gear inches) are the same - his reason for changing the middle ring - one rev of the cranks yields the same for distance traveled for both bikes.
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    Powertap accuracy?

    Say, about those powertaps and the 1.5% accuracy that is claimed. Is this between units or they are within 1.5% of themselves? What I mean is if I run absolutely identical runs, will my unit be up to 1.5% different? Or if I run and identical run to you, will our different powertaps be within 1.5%?

    And if it's not between units then what is the difference between units? Because if it's >2% then maybe the fuel just got the higher-reading hub.

    On the other hand, the data is better than "29" wheels should roll faster" and "26" wheel accelerate faster" and "29" wheels are better on the tougher terrain <than a 26" dually?>".

    Maybe we should ask him to do some runs then rebuild the wheel really quickly and do some more runs. Probably several times (rebuilding) would be best. <-sarcasm!

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    The real bottom line here is regardless of how much energy Dave used, on this day on this course he was faster on his 26" wheel bike, and two of his 3 slowest laps were on the 29er, for whatever reasons.

    In a race there are no bonus points for amount of energy (not) used. Time/distance is all that matters.
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    That's a good point

    excellent point, I seemed to miss it until now. Maybe a lot more 24 hour lap races and just looking at the times only would be a decent measure for a guy and his 2 bikes. But for now I guess the 29" softtail will have to be behind the 26" dually on that course for that guy.

    Quote Originally Posted by shiggy
    The real bottom line here is regardless of how much energy Dave used, on this day on this course he was faster on his 26" wheel bike, and two of his 3 slowest laps were on the 29er, for whatever reasons.

    In a race there are no bonus points for amount of energy (not) used. Time/distance is all that matters.

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    impressions

    1. the issue of powermeter accuracy between units is a good one.

    2. isn't a trek fuel a fairly advanced piece of bicycle engineering application - and ( sorry to say ) softails in general and aluminum ones in particular just a kinda . . i dunno . . . . hacked together concept from the git-go? if we left the wheeelsize out of it, would anybody find this result at all surprising ?? i certainly wouldn't.

    3. 2 minutes is huge. no racer who is at all paying attention would need a powermeter to tell them one bike is 2 minutes faster than another, over and hour or so lap. 2 minutes is basically and obviously riding away, one from the other, and you could literally just watch how fast the trees ( cactus ) are going by on each lap to tell the difference. if 26ers were in fact - or 29ers were in fact 2 minutes faster over a closed course the world would know about it by freaking now, and it would not be a debatable subject. it would be like debating whether or not aero-bars are faster for time trialling on the road at 25 mph - just not at all in question. the difference a disc wheel and aero-spoke front gives you on the road is around 2 minutes over an hour- does anybody need a powermeter to tell them that a disc/aero-spke wheel set is faster for TT use? the answer is no - a bike inherently 2 minutes faster than another will FEEL like a rocket ship underneath you, me, or anybody and would not require further discussion on the matter one bit.



    ad this all together and what is my impression ? a guy was out goofing off in the desert with some powertaps. he seems like a nice enuf guy, could easily be any of our racer-buddies. i bet he rides his fuel pretty smooth. and an aluminum soft-tail today is a sorta weird concept for a bike just as it has always been that might be fun to ride if you like that sorta thing, but a smooth-ridin guy as fit as you on a fuel will beat you if you race him on it. thassit.
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    Most likely the 29er has a higher center of gravity. This meant Dave had to take turns slower than on his 26er. Presumably, he had to increase power to make up for this time loss. The larger, heavier wheels require more watts on ascents and acceleration. Plus there are plenty of other variables. What about those tires? Do they really offer the same amount of grip and rolling resistance? How much energy is lost using the more compact crank compensating for the larger wheels. Some valid points have been made in this thread. All this article makes clear is that Dave was faster on his 26er and his dos niner w/power tap is for sale. It's really just a story about Dave Harris, not 26 vs. 29".

    IMO, if someone is serious about racing then he should have one of each bike. A few days before each race, check his times on each bike and then use the fastest one on race day. It's fair to say that some courses favor the 26" wheel, others the 29" wheel.

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    P. S.

    ya know, on review . . . . . . . if a guy was of a suspicious nature . . . . . . . . . . . . . . i hate to say it but i do think on balance there could be reason to at least slightly suspect that this dude was - perhaps, just perhaps - a wee bit less than perfectly objective about this test goin' in. re-read my point # 3 above, and think about it. in fairness, i will say i work in corrections and basically get liied to everyday all day 40 hrs a week and as a rsult i am am a suspicious a$$ mofo. could well be dude is on the up and up. just sayin' . . .

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    Quote Originally Posted by FastMovingTarget
    Most likely the 29er has a higher center of gravity...
    Not really. The Dos Niner has a lower BB than the Fuel and most of the bike/rider weight is in the rider anyway
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    Quote Originally Posted by Ricky J
    While riding today, the mind began wondering: just what sort of trail or course would most hobble a typical 29er? I think it's a tight venue where you're always either accelerating or braking hard on a smooth surface with traction not limiting, and where turns are configured to minimize the carrying of corner speed. Basically, a place where none of the usual 29er advantages come into play and the upper hand simply goes to machines with less rotating weight to start and stop, the 26" bike. You could actually make a rudimentary form of this course in a parking lot just for kicks! Even better, then use stick-on wheel balancing weights to make the 26" wheels heavier and repeat the contest- the 29er should now win. Shock! Horror! Or how 'bout mtb drag races? I'll bet the 26 nails every holeshot, with the 29er owning trap speed honors.
    I've had similar thoughts. What would a 29"-hating race promotor have to find as a course to piss me off? If he managed to make a course so smooth and tight that I'd feel hampered on my 29" bike, well the 26" standard as an ideal comes in jeopardy too. If it's that tight, what limits me most is the location and width of my shoulders, tall and broad. Especially if trees are replaced with cacti. As a tall dude, I need to ride wider lines around them, and if the room's not there, I need to slow down.
    Build me such a 26"-friendly course, and I'll win the race a 24".
    The only "realistic" thing I can think of it to dig lateral shallow ditches in the course, dug by a showel who's shape would perfectly fit the 29" wheel. But also then, a 24" bike will do better over that than the 26" bike.

    If any of my calculations are right, and air drag would never be a factor for 26 vs 29, the 29"er should win dragraces anyway, because the rolling resistance advantage is larger at any speed than the effect of the weight difference in the wheels. Especially because a rider is so much heavier than a bike. If bikes were Herbies but with equal engines, yes, the 29" would come off the line slower and then start to make up ground and eventually overtake. Throw on a rider, and rolling resistance becomes a much larger factor, the weight difference between the two gets lots behind the comma.
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    Frankly I am not all that surprised at these results. If 29ers were as superior as the 29er crowd would have us believe, the racing world would have adopted them much faster. I think it remains a matter of rider preference and greatly depends on the terrain where the bike is used.

    I do think 29ers are to 26ers what FS is to Hardtail, meaning they offer a smoother ride. But racers don't give a crap about smooth. They only talk in terms of efficiency.
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    What's always been a bad thing for racing 29"er has been that the tires that the 26" forlks are running just don't come in 29". "We" consider the WTB Nanoraptor (decade old tread?) a fast rolling tire with nice grip. Count the 26" Nano's in a big Expert race. The Kenda Karma just hit the market, wondering what effect that one will have, whether it's racey enough to get people scratch their heads any more.

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    So Dave figured out for himself that riding a 26 FS bike takes slightly less power than a 29er softtail on a particular course. Good for him.

    Did everyone already forget Jeremy Horgan-Kobelski and Travis Brown testing 29ers back to back with 26ers, and discovering that they only "felt" slower, when in actuality they were riding faster? Did we already forget that they're planning on possibly riding 29ers in specific NORBA Nats that might suit the big wheels?

    There are plenty of racers who have tested their bikes head to head and come up with different conclusions. Personally, I've made up way more than 2 minutes through climbing technical pitches that others on 26ers had to walk...

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    He seems to be estimating that he will be slower based on power output, but I think you would have to do a least 3 runs each to find a median, then make a comparo.

    Nothing is mentioned about contact patch which is certainly increased on the 29r and therefore gives a little more resistance when pedaling. And because of this increase diameter/contact patch the estimate also does not account for possibly higher speeds on the 29r over rocks, roots, and in corners which may in turn make the 29r faster overall.

    For me I think the trail is a hard place to view "overall" wattage. It's too inconsistant IMO.
    Now maybe Lance can do this, but he uses a wind tunnel because a few gusts of wind can make up for the extra watts needed.
    Maybe that was this case? Maybe he was moving a few miles an hour faster and that extra wind resistance added the extra energy needed??
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    Quote Originally Posted by serious
    Frankly I am not all that surprised at these results. If 29ers were as superior as the 29er crowd would have us believe, the racing world would have adopted them much faster. I think it remains a matter of rider preference and greatly depends on the terrain where the bike is used.

    I do think 29ers are to 26ers what FS is to Hardtail, meaning they offer a smoother ride. But racers don't give a crap about smooth. They only talk in terms of efficiency.
    Im suspect that the big picture lies in the bike industry. Redesigning and retooling is not cheap. May be that the bigboys want to get some milage out of their present 26" process. They don't seem to be talking much about the 9er movement and this may be a good sign since they are not belittling the 29er. To bellittle would make them look foolish when time comes to produce them. I know that If I was a big manufacturer, Ide wait til the light was full green before I put my design to metal and suck all I could out of the present 6er manuf. It just makes good business sense. It seemed to happen the same way when the full-susp movement began. Just a thought.

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    Quote Originally Posted by F5000sl
    Nothing is mentioned about contact patch which is certainly increased on the 29r and therefore gives a little more resistance when pedaling. And because of this increase diameter/contact patch the estimate also does not account for possibly higher speeds on the 29r over rocks, roots, and in corners which may in turn make the 29r faster overall.
    Bingo. This is exactly what I was thinking. The increased contact patch of the 29er is not always good. How often do you lose traction on a 26er? How often are you unable to steer on a 26er? IMHO, neither happen very much. On the other hand, a larger contact patch means (assuming the tires are run at the same pressure) more tire to pull off the ground on every pedal stroke, so more watts. Isn't this why roadies all try to run a thin tires as possible without making the bike completely unrideable?

    I would think that a different type of tire for the 29er, or higher tire pressure on the 29er wheels would cure the problem. Of course, higher tire pressure would mean less shock absorption and less comfort, but racers don't care about that.

  45. #45
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    Tires at the same pressure have the same size contact patch, no matter the diameter or width (within reason). The shape will vary, but not the size (area).
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    This thinner contact patch, I could imagine, seem to make a good center tread more important on a 29" tire to roll well. all the weight of the bike is concentrated close to the middle of the tread.
    Perhaps this works out better for rolling rsistance in some conditions than others?
    Over the whole, larger wheels just roll faster, or shopping carts would be winning monstertruck races.

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    Huh?

    Quote Originally Posted by Maxrep
    In theory, yes. In a comparison of 26 and 29 inch tires with knobbies.....no. The comparison you stated above holds true with slicks, but changes more than slightly for tires with knobs. Lets examine:

    a 150lb rider sitting astride his 26 inch XC pro equipped bike, has 10 knobs on his front tire that are in contact with the ground. This same rider then sits on a bike with 29 inch xc pro tires(just imagine). Now there are 12 knobs in contact with the ground. HUH!!?? The rider did not gain weight, and the tire pressures between the bikes were identical, so what gives.

    The 29er tire has a different angle of attack. The twelve knobs that support it, do not bear quite the same load as the ten knobs supporting the 26er. A 50inch diameter XC pro wheel may have 18 knobs in contact with the ground with the 150lb rider. Each knob would bear a much lighter load than the 26 inch tires ten contact knobs.

    Think on this for awhile. Slicks of differing diameters, more closely adhere to Shiggy's statement about identical contact patches. Once knobbed tires of differing diameters are examined, individual knob load pressures will change with "Angle of attack", causing taller wheels to spread their load over more knobs.

    For this reason, a less aggressive or faster rolling tread style on a 29er can yield the same traction as a more aggressive 26 inch tire, within reason.

    P.S. Before you reply that I am wrong in regards to the knobby contact patch, give it some thought. I am confident there will be a few who will agree .
    Didja actually go air up two tires, same model tread pattern, one in 26" and one in 29"? Same pressure, park 'em in paint and sit the same 150lb rider on each. Same rim profiles even. But by definition, PSI is PSI, that is each square inch of tire contact supports so many pounds of bike/rider. Give it some thought. I am confident there will be a few who will agree. "Knob load pressure" indeed.

    As to angle of attack, see Mastershakes succinct post here:

    http://forums.mtbr.com/showthread.php?t=170411&page=2

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    That is still because of the shape change, not a size/area change. The actual number of knobs in the contact patch (which I did not claim was the same or not) depends on the tread design. For the same tire width the larger diameter should have more center knobs on the ground and fewer edge knobs. On surfaces softer than total hardpack we can be back to full contact of casing and tread.
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  50. #50
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    Quote Originally Posted by Cloxxki
    This thinner contact patch, I could imagine, seem to make a good center tread more important on a 29" tire to roll well. all the weight of the bike is concentrated close to the middle of the tread.
    Perhaps this works out better for rolling rsistance in some conditions than others?
    Over the whole, larger wheels just roll faster, or shopping carts would be winning monstertruck races.
    I don't agree in all cases.

    Larger wheels transmit power to the ground faster (more torque), and they roll over obstacles better because of their angle of attack. Look at dragsters, the big wheels are in back and little ones in front. With your theory, they should have big wheels in front too. The rear wheels are powered through a transmission to the engine, thus they are an optimal size for power transmission. On the other hand the big wheels on monster trucks are there to roll over objects. Put some objects in the way of a dragster and you will find the dragsters running larger wheels up front.

    So big wheels are better at rolling over objects because of their lower angle of attack (any monster trucker knows this) . But they also have a longer contact patch. This means more traction and unfortunately, more drag on the ground. You don't get something for nothing.

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    The front wheels on teh dragster are small mostly because they are not use foranything but keeping the front from dragging the ground :-)

    What I was getting at, the center tread of 29"er gets more action than with 26". Tires might be designed specifically with that in mind.

    Maxrep and Shiggy seem to both be right.
    If soft conditions, when all knobs that tough the trail are more or less fully penetrating, footprint will look much the same. A non-rolling 29" wheel always longer of course. But which will sink deeper at a given speed? And what does that do to RR?
    With soft trails, does the angle of attack, or rather the hub's leverage on the knobs become a factor that lowers rolling resistance, or is that effect cancelled out by the different angular speeds between wheel sizes? Retracting a knob from soft soil costs lots of energy...

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    If we assume it's true that...

    the bigger wheels in fact do take more power to accelerate and go the same speed as 26" wheels then in fact thin & light lower powered climber types probably won't be putting them to good use.

    Conversely, if more powerful guys can get them up to speed and decelerate less (and less often) maybe they can find an advantage riding 29"ers in an endurance race. The more effort to accelerate them thing will be a hard thing for racers to contend with if true. Thankfully I just ride mine for fun, fresh air and exercise.

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    Not the best prints (dirty wet tires on paper toweling).
    Both are Jones XR 2.25 fronts.
    Both mounted on a 22mm wide rim.
    Both inflated to 32psi.
    Both on the same bike with the same body weight applied on a hard smooth surface.
    You tell me which is the 29" and which is the 26".
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    Don't know

    Quote Originally Posted by shiggy
    You tell me which is the 29" and which is the 26".
    Don't know, they look the same! Everybody spouts off about the different contact patch, now that's a pretty big question too. Or maybe not, how much do you figure we can trust the data

    Shig, you are the freakiest tire freak out there, thanks for airing those suckers up

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    Great stuf Shiggy, finally someone that will get his hand dirty!

    Next test please in a bath of consistant clay. :-) Wheels both weighed onto it with ~95lb on it, the average of a wheel for an average rider?
    It will be interesting to see how clay thickness affects any contact path differences.

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    Wel, which is the 29 and which is the 26?

    Make your guess, which is the 26, and which is the 29? Shiggy really hasn't helped with the "amen", but really showed how PSI means PSI. Can't imagine either of those contact patches make a lick of difference, much as Mastershake (earlier link) showed how insignificant angle of attack differences are(n't) between 26 and 29.

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    Quote Originally Posted by Fastskiguy
    Say, about those powertaps and the 1.5% accuracy that is claimed. Is this between units or they are within 1.5% of themselves? What I mean is if I run absolutely identical runs, will my unit be up to 1.5% different? Or if I run and identical run to you, will our different powertaps be within 1.5%?

    And if it's not between units then what is the difference between units? Because if it's >2% then maybe the fuel just got the higher-reading hub.

    On the other hand, the data is better than "29" wheels should roll faster" and "26" wheel accelerate faster" and "29" wheels are better on the tougher terrain <THAN a dually? 26?>".

    Maybe we should ask him to do some runs then rebuild the wheel really quickly and do some more runs. Probably several times (rebuilding) would be best. <-sarcasm!
    Powertap literature says 1.5% accuracy, which means there's a 68% chance the correct value is in the range +/- 1.5%. But that's immediately after calibrating. I would bet that he did not calibrate for every lap and the change in temperature is sure to be big in a 24 hour race and in power tap readings.

    Is 2 minutes important? Check out Glenzx's report of Old Pueblo. Differences of 40 minutes per lap - ignoring the 3:30 lap.

    The data isn't accurate enough to help zealots of either side, 26 or 29.

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    Quote Originally Posted by Cloxxki
    What I was getting at, the center tread of 29"er gets more action than with 26". Tires might be designed specifically with that in mind.
    Yes. That would be interesting. I think when 29er riders look at tires, we should pay closer attention to the center surface. The topography of the center of the tire will affect traction (and also resistance caused by having to extract lugs from the ground) to a greater degree on 29er bikes. Whereas the topography further from the center of the tire will have the same effect on 26er tires. It is all in the tire design. I guess you could design a tire which has a greater contact patch on a 26er than on a 29er -- if you kept the center smooth and put all the lugs toward the edges. Sort of like a Maxxis Worm Drive. I remember how fast those Worm Drives were when I was commuting to work on them.

    Quote Originally Posted by Cloxxki
    If soft conditions, when all knobs that tough the trail are more or less fully penetrating, footprint will look much the same. A non-rolling 29" wheel always longer of course. But which will sink deeper at a given speed? And what does that do to RR? With soft trails, does the angle of attack, or rather the hub's leverage on the knobs become a factor that lowers rolling resistance, or is that effect cancelled out by the different angular speeds between wheel sizes? Retracting a knob from soft soil costs lots of energy...
    I wonder if there is any suction effect as well. On wet trails, I often feel like I my tire wants to stick to the trail like velcro. I noticed this especially with the Exiwolf. I think the Exi is a great dry condition tire but a slow tire for wet conditions.

    In any case, we all agree that the 29er foot print is different (longer), so it utilizes the tread pattern differently. So using the same tread pattern on both 29ers and 26ers will have different effects on each platform. Using the exact same tire on both bikes is a bit like comparing rifle ballistics of two different caliber rifles with the same caliber bullets. Do you want to use the same caliber of bullet in two different caliber rifles to make it a fair comparison? No. You want to use bullets optimized for each rifle. If you want to make a fair comparison between two bicycles with different size wheels, you need to optimize the tire for the platform so that they perform similarly.

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    Quote Originally Posted by shiggy
    Not the best prints (dirty wet tires on paper toweling).
    Both are Jones XR 2.25 fronts.
    Both mounted on a 22mm wide rim.
    Both inflated to 32psi.
    Both on the same bike with the same body weight applied on a hard smooth surface.
    You tell me which is the 29" and which is the 26".
    Nice test. But the fact that you didn't use Bounty towels invalidates the test completely.

    But really, even if the contact patch isn't larger, everybody knows the contact patch is longer (even on smooth tires) and will utilize the tread differently. Try comparing a smooth 20 inch foot print with a smooth 29 inch foot print. The 20 inch tire will bulge along its width more than the 29 incher. It just makes sense.

    Are the 29/26 inch contact patch differences minor? I don't think so. We are talking about riding bicycles for miles and miles here. How many wheel rotations are in a mile? Even the slightest difference will be amplified by how much it reappears.

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    If watts expended...

    are the whole story in cross country endurance racing then wouldn't it be an advantage to go to even lighter and even faster accelerating 24" inch wheels?

  61. #61
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    Area

    Right is 29 is my quess.
    The area of both prints should be the same I think, I expect the 29r to be longer, less wide. Please tell me if I,m wrong.

    ps How would this print look with wheel diameter 290 FEET?

    Quote Originally Posted by shiggy
    Not the best prints (dirty wet tires on paper toweling).
    Both are Jones XR 2.25 fronts.
    Both mounted on a 22mm wide rim.
    Both inflated to 32psi.
    Both on the same bike with the same body weight applied on a hard smooth surface.
    You tell me which is the 29" and which is the 26".

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    Look at Shiggy's Bounty Quicker Picker Upper (tm) shot...

    Quote Originally Posted by Maxrep
    The "Amen" will come from someone who understands. The increase of contact knobbs will be on the order of 10-12%. Additionally, the knobbs on the 29er are in contact with the ground longer than the 26 inch knobbs. This provides a more stable anchor with the soil. The 29er knobbs also do not change their angle of contact with the soil as abruptly as 26 inch knobbs. The result is better traction.

    Suffice it to say, I am right and you are wrong.

    Let me draw you a mental picture: There is a ten foot tall XC Pro next to a 26 XC Pro. All being equal, do the tires still have the same number of knobbs contacting the ground? Still don't get the picture? Keep increasing the size of one of the wheels, but not the width, and let me know when the light bulb comes on!

    I think I count the same lug numbers, looks pretty much the same to me, I couldn't hazard a guess as to which is which.

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    Quote Originally Posted by Maxrep
    The "Amen" will come from someone who understands. The increase of contact knobbs will be on the order of 10-12%. Additionally, the knobbs on the 29er are in contact with the ground longer than the 26 inch knobbs. This provides a more stable anchor with the soil. The 29er knobbs also do not change their angle of contact with the soil as abruptly as 26 inch knobbs. The result is better traction.

    Suffice it to say, I am right and you are wrong.

    Let me draw you a mental picture: There is a ten foot tall XC Pro next to a 26 XC Pro. All being equal, do the tires still have the same number of knobbs contacting the ground? Still don't get the picture? Keep increasing the size of one of the wheels, but not the width, and let me know when the light bulb comes on!
    The tallest XC Pros I know of are Ryan Trebon (6' 5") and Barry Wicks (6' 4").

    Wildly increasing the tire diameter is not needed to turn on the light.
    I am not trying to disclaim that larger diameters have an advantage.

    I understand your theory and agree with the premise. It is what has been said about the difference between the sizes from the beginning. I never claimed this was wrong.

    But it is not an increase of the area of the contact patch, it is not an increase in the number of tread elements on the ground.

    It is a change in the shape of the contact patch (slight). It is a change in which tread elements are on the ground and it is a change in the angle of contact and departure.
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  64. #64
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    umm,

    Quote Originally Posted by shiggy
    The tallest XC Pros I know of are Ryan Trebon (6' 5") and Barry Wicks (6' 4").

    Wildly increasing the tire diameter is not needed to turn on the light.
    I am not trying to disclaim that larger diameters have an advantage.

    I understand your theory and agree with the premise. It is what has been said about the difference between the sizes from the beginning. I never claimed this was wrong.

    But it is not an increase of the area of the contact patch, it is not an increase in the number of tread elements on the ground.

    It is a change in the shape of the contact patch (slight). It is a change in which tread elements are on the ground and it is a change in the angle of contact and departure.

    Amen?

  65. #65
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    Quote Originally Posted by Maxrep
    The "Amen" will come from someone who understands. The increase of contact knobbs will be on the order of 10-12%. Additionally, the knobbs on the 29er are in contact with the ground longer than the 26 inch knobbs.
    So if I ride for an hour the knobs will touch the ground for 66 or 67 minutes? Wow!

    Quote Originally Posted by Maxrep
    Let me draw you a mental picture: There is a ten foot tall XC Pro next to a 26 XC Pro. All being equal, do the tires still have the same number of knobbs contacting the ground? Still don't get the picture? Keep increasing the size of one of the wheels, but not the width, and let me know when the light bulb comes on!
    All things being equal <b> including the weight </b>, the contact patch will be the same. The tire supports you load over a certain amount of contact patch, and the force supporting the load comes from the air pressure of the tire. So do the math - force times area equals pressure. If the force (i.e. the load) and the pressure stay the same, how can the contact patch area vary?

  66. #66
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    I think you are partially right about the resources, design changes, mold/tooling changes - the small custom guys can change and react quickly to market trends though and I still see them driving the business. Smaller companies can do this too without having a big company weighing them down. Look at anyone who can build bikes...these guys are driving the sales at this point - Fisher too since they were "first to market" and will probably always be one up. Kind of like hydration packs...who do you think of first?

    Big guys have too many "internal" struggles to face...and lets face it if companies are testing the water now then they won't have anything earliest until next year. Look at Niner - they are the perfect example of a small company growing fast. They are not held down by big organizational BS like Board of Directors, ROI, Phase reviews, engineering changes, heavy Market Research, etc. etc.etc.etc. One business/marketing guy and one design engineer to keep things simple and a good eye on the market. 4 or 5 frames in a year? Tha'ts pretty huge.

    Look at the hand built bike show coverage pics if you haven't - EVERYONE pretty much had a 29"er in their booth. That tells me the demand is still huge and a growing market. Will the big boys come out w/ 29"ers? Probably, but the volume is pretty low so I would expect to see one model to "test the waters" with.
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  67. #67

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    My take,

    I doubt very seriously that we'll ever see a scientifically controlled test sufficient to satisfy everbody -- strong beliefs seem to frequently trump science anyhow. I have absolutely no doubt that I can accelerate my 26" 22.88 pound Moots Smoothie faster than my nearly equal weight Moots Mooto-X 29er (both built with AM Classic wheels and relatively light tires) I'm 5'10" and 130 pounds with a good spin but not a lot of power. I loose LOTS of time racing or hammering with friends on twisting courses that require a lot of accelerating out of corners when I'm on the 29er. I hang on the 26er. On the other hand, I'll take the 29er any time for technical fun runs. Works for me....but I'd never suggest that it proves jack for the masses.

  68. #68

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    It's gotta be a compromise -- 24" wheels would likely start hurting time because of poor performance in technical sections.

  69. #69
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    interesting to plot those on a l'abbe plot

    and see what the overlap is....


    www.statsdirect.com/help/l_abb__plot.htm


    Quote Originally Posted by shiggy
    I wonder why the results on the Fuel vary so much.

    He had a group of four laps (4, 11, 12, 13) with times between ~65min (12) and ~67:30 (11) and power from ~182 (13) to ~192 (4).

    The lap with the highest power output is third fastest (4).
    The lap at the lowest power is second fastest (13).

    Why was the Fuel 2 minutes faster on lap 12 at slightly less power than it was on lap 4 (3% faster, 0.5% less power)?
    Why was it 30 seconds faster (0.75%) on lap 13 with ~5% less power than it was on lap 4?

    The power and time difference between lap 12 (fastest) and lap 11 (slowest) are both ~3.7%
    All said, the results are hardly conclusive. Too many other variables. The only thing that is certain is both of his laps on the Dos were slower than most of the Fuel laps.
    For a rock steady Gas Tank bag > the DeWidget

    bit.ly/BuyDeWidget

    https://www.instagram.com/drj0n_bagworks/

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