29er: Climbing Fire Roads

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  • 29er: Climbing Fire Roads
  • Premier Icon charliemort
    Subscriber

    I’ve heard this too, and my 29’er Salsa Fargo sure as hell feels faster up fire-road type stuff than my 26’er Yeti 5 (but a lot of variables there beyond wheel size), but can’t say it makes sense to me either

    Premier Icon wwaswas
    Subscriber

    Extra rotating weight of the wheels keeping momentum up if your pedalling isn;t as smooth as it could be?

    Could just be down to suspension design, if the Gyro tends to stiffen up under pedalling load it’ll make it more efficient at turning pedal strokes into forward motion.

    franki
    Member

    I guess it’s the larger diameter wheel rolling better.(Not a very scientific answer, I’ll grant you.)
    I’ve got similar 26″ & 29″ singlespeeds and the difference on long climbs is quite clear.

    trail_rat
    Member

    your in aberdeen right ?

    you know the wind has died down – you probably had a tailwind on the gyro and got back on the trance now when there is no wind….

    asterix
    Member

    perhaps we should change all the powerstation flywheels for bigger ones so we could magically generate more electricity for the same amount of fuel/cost πŸ˜‰

    Purely how it feels to me, but my 29er seems to have a less ‘spikey’ power transfer than my old 26er (which kinda felt on-off-on-off), meaning that power transfer through the pedals feels smoother with more ‘supplese’. That then feels like the power strays on all the way through the pedal rotation.

    Does that make sense?

    Premier Icon wwaswas
    Subscriber

    asterix is really backing up what I was saying – the flywheel effect of a larger/heavier wheel will smooth things out. You don’t gain power (obviously) but it may make the transfer more effective.

    In the same way they don’t put flywheels the size of a 10p on car engines.

    I would imagine this thread is going to go the same way as all the other 26 v 29 threads, even though it is asking about one particular set of circumstances.

    I don’t think we will ever know the answer until someone does some back to back tests on otherwise identical bikes with PowerTaps or similar.
    In fact, considering the marketing budgets of the big manufacturers, it’s surprising none of them have done this to prove that their new bikes really are better than their old ones.

    Or have I missed it somewhere ?

    Premier Icon jameso
    Subscriber

    I don’t think we will ever know the answer until someone does some back to back tests on otherwise identical bikes with PowerTaps or similar.

    Thehy have, it’s just non-conclusive as it’s far to variable to have any meaning really. And there is no ‘better’. Just a different feel, pros-cons.

    And we all know 29ers were designed and popularised by fire-road lovin’ yanks right? )

    Premier Icon Capt. Kronos
    Subscriber

    I have found this too – you get upto speed and the thing just keeps on rolling. I am more knackered at the end of a ride, but I have done it much faster!

    mattbibbings
    Member

    I don’t think we will ever know the answer until someone does some back to back tests on otherwise identical bikes with PowerTaps or similar.
    In fact, considering the marketing budgets of the big manufacturers, it’s surprising none of them have done this to prove that their new bikes really are better than their old ones.

    Or have I missed it somewhere ?

    They haven’t done this because they all still sell all the wheel sizes. Simple.

    Thehy have…

    I did miss it then. Have you got a link to it ?

    ormondroyd
    Member

    You’re probably not having to reaccelerate the wheel as much over small bumps, but really, 2lbs is not a lot of difference. It’s less than a litre of water in a camelbak, for instance.

    …far to variable…

    I think you are missing the whole point of doing such a test.
    The idea is to eliminate all the variables as far as possible, apart from the obvious one of wheel size.

    GEDA
    Member

    Maybe it is the gearing. The same gearing is essentially higher on a 29er.

    asterix
    Member

    but, in the end, you don’t have any more input power so you can’t go any faster can you

    like CaptKronos says “I am more knackered at the end of a ride, but I have done it much faster!”. OK there you have it, a certain bike might tempt you to push harder and if so then you may go quicker, but you have had to put more effort in. If you don’t put more effort in then there isn’t some magical gain to make

    Steve-Austin
    Member

    Have you found you are more attractive to women when riding the 29er?

    Premier Icon roverpig
    Subscriber

    Yes, I know, another flipping 29er thread. Surely we’ve done this to death by now. Unfortunately I can’t find the answer to this specific question though, which relates to sped up long draggy fire road climbs.

    Following a four day test on an Orange Gyro I’ve been getting back on my 26″ Trance and going back over some of the same trails for comparison. I wont bore you with all the details. Suffice to say that there are advantages and disadvantages to both. Neither are better, it’s just a case of picking the best set of trade-offs for you. But the one thing that is bothering me is the extra speed of the Gyro climbing simple fire road climbs. We’re not talking technical climbs (where traction would be a key) or even excessively steep ones (where the size of the bottom gear might come into play), but boring fire road slogs.

    How can a bike that is 2lb heaver (with virtually all of that extra weight being in the wheels) be faster up a relatively smooth climb? It doesn’t make sense and I’m tempted to dismiss it as just being a case of me pushing a bit harder. But I wanted to check that there wasn’t actually some known technical reason that I’m overlooking.

    GaryLake
    Member

    Maybe it is the gearing. The same gearing is essentially higher on a 29er.

    That’ll be a factor on the steep stuff where he will be mashing the granny ring with no ratios left to grab at, but assuming he’s in the middle of the gear range on a simple fireroad it won’t.

    I’d put it down to purely ‘feel’, now that feel might make you go faster of course. I’d expect the Gyro feels like it has more momentum, feels smoother, and therefore it’s easier to keep your head down and the power on.

    I do find it easier to keep my rhythm and cadence strong and consistent on the 29er which probably counts for something. On a 26er I always feel a bit stabby and short on Torque, which probably leads me to generally be less efficient and probably slower.

    Roverpig, can I be the first to say, buy the effing bike already! πŸ˜‰

    Have you found you are more attractive to women when riding the 29er?

    Tsk, this is a given…

    michaelmcc
    Member

    Answer is simple, its cuz 29ers a better πŸ˜› .. thread closed.

    Premier Icon christhetall
    Subscriber

    One of the key aspects of 29ers is that they are faster over less challenging terrain, which is why they are so popular for XC racers.

    Simple flywheel physics – harder to accelerate, but better at maintaining momentum (there used to be a good article on the subject on chevin cycles website, but it seems to have disappeared)

    Back in day TDF riders would drill holes in their bike frames to make them lighter, but didn’t use smaller wheels

    Premier Icon zippykona
    Subscriber

    On my climb on the way home I’m always in a higher gear on my 29. It feels like im going slow but obviously not.

    Wozza
    Member

    I wont bore you with all the details. Suffice to say that there are advantages and disadvantages to both. Neither are better, it’s just a case of picking the best set of trade-offs for you.

    About the most sensible thing I’ve read on here, ever.

    Sam
    Member

    less rolling resistance, better conservation of momentum.

    Back in day TDF riders would drill holes in their bike frames to make them lighter, but didn’t use smaller wheels

    I seem to recall Jaja having a 650c climbing specific bike BITD when he was targetting the mountains jersey.

    Premier Icon jameso
    Subscriber

    MTG, the problem is the terrain, riding styles, wants/preferences are all so variable. Remove them and it’s just down to the mechanics of wheel mass. But the law of conservation of energy are not variable ) so I think we’re only talking about improved efficiency or suitability for some riders based on ergonomics, or food for German bike mag features.

    VanMan
    Member

    Maybe you should put them both on a running machine to eliminate the variables

    ormondroyd
    Member

    And also a plane on the adjacent treadmill to see if it takes off

    drofluf
    Member

    Steve-Austin – Member
    Have you found you are more attractive to women when riding the 29er?

    He’ll need to singlespeed it as well for that to happen πŸ˜€

    Premier Icon aracer
    Subscriber

    It’s because climbing fireroads is boring. Everybody knows that 29ers are better at the boring bits and 26ers better at the fun stuff (650b is better at lining marketing men’s pockets).

    I would imagine this thread is going to go the same way as all the other 26 v 29 threads

    HTH

    Premier Icon roverpig
    Subscriber

    Thanks folks, for at least kind of keeping to topic πŸ™‚ There are quite a few points to pick up there:

    Wind/Weather: You can never rule that out, but I don’t think it was a factor here. Most of the segments I’ve looked at for comparison where in trees to try and take the wind out of play and there is one (what Strava calls “Long drag back to the car park” at Pitfichie) where I was going against the wind (and was also knackered after four days of test rides) and still recorded a personal record, which is what got me thinking.

    Flywheel effect: I’m afraid I just don’t buy this one. If a higher moment of inertia made climbing easier we could all just fit heavier tyres to our 26″ bikes to get the same effect. In fact we all try to make out wheel as light as possible, for good reasons.

    Suspension:[/u] This could be factor, but when I tested a Five against the Trance the Trance was clearly faster. So there is more going on than just the “stiffening of the single pivot under pressure” thing. I’m also still seeing the effect if I select climbs where I had both bikes “locked out”.

    Higher gearing on a 29er:[/u] That was a factor on some steep climbs where I ran out of gears, but I’m talking here specifically about the more draggy climbs where that wasn’t an issue.

    29ers are just better, more boring etc:[/u] No they’re not.

    Subconsciously trying harder:[/u] Since I can’t test the bikes blind I can’t rule this out. In fact I think this should be the default explanation unless it can be ruled out.

    Rolling resistance:[/u] This hasn’t been touched on much, but I wonder if it could be a factor. The larger total air volume in the 29er tyre presumably means less deflection in the sidewall and less losses there. It’s hard to imagine that it could amount to much though. Although combined with the ability of a larger wheel to roll over small bumps better(and even fire roads aren’t totally smooth) I guess it could be a factor.

    The lack of any decent scientific tests is both frustrating and interesting. There is lots of science that doesn’t get done simply because the people funding it are worried about a negative result and that could be a factor here. I recon we need a greater uptake of 29ers in Germany. Then we’ll see some lab tests.

    Oh and GaryLake[/u], you sound like my wife πŸ˜€

    Premier Icon Trekster
    Subscriber

    Thanks to Dales bike centre I recently tested 2 x 29ers, Rumblefish and 529

    I struggle on hills due to dodgy back and knees but found the ‘fish an easy pedal up the first road climb away from the centre.
    The 529 on the other hand felt like my old Kona Dawg but with that horrible chain stretch feeling. The more I tried to pedal softly to eliminate the chain stretch feeling the slower I went!

    Sounds more like a battle between 2 bikes than 2 wheelsizes.

    wrecker
    Member

    A mate completely overhauled me on a rented camber 29er on fireroads recently. He hated it in corners though, and despite being 6ft4 has decided not to go 29.

    b45her
    Member

    no one seems to have mentioned the mental aspect, i don’t know about you but i usually know what gear i like to be in for different climbs and stick to it, could be that subconsciously you know you can push 32×25 gearing up a certain hill so did the same on both bikes with the slight change in speed being due to the wheel diameter being bigger.
    without a powertap its impossible to know.
    i have a strong suspicion that powertaps have been used on different wheel sizes but the data not published because there was bugger all difference, more speed for a given power output would be a marketing mans dream there’s no way they wouldn’t use it.

    One of the key aspects of 29ers is that they are faster over less challenging terrain, which is why they are so popular for XC racers.

    I beg to differ.

    Over ‘less chalangeing terrain’ smaller wheels would win, assuming higher speeds and more aerodynamic drag. Look at moultons, banned by the UCI for being better than their big wheeled cousins.

    The problem (sometimes) comes with trying to package the bigger wheels into comparable frames/forks. But then DH bikes tend towards long chainstays anyway so I suspect their resistance will be short lived. But IMO it’s also just what people are used to, if we’d started with 29″ wheels we’d complain that 26ers had twitchy handling only suited to tame courses.

    Premier Icon christhetall
    Subscriber

    Re the flywheel thing, it’s 30 years since I did my physics O level, but I got an A so that makes me an expert πŸ˜€

    I’ve got a feeling that its not about the weight but the position of the weight relative to the centre

    This and other factors explained better here
    link

    b45her
    Member

    truth ^^^

    @thisisnotaspoon
    i don’t buy the whole moulton argument the uci rules state that wheels can be as small as 20.5″ including tyres if the smaller wheels were faster the pro tour teams would be using them especially the likes of sky with their love of “marginal gains”

    i don’t buy the whole moulton argument the uci rules state that wheels can be as small as 20.5″ including tyres if the smaller wheels were faster the pro tour teams would be using them especially the likes of sky with their love of “marginal gains”

    Teams only use what the manufactures want to sell apparently. So if pinarello made a 21″ wheel they would. πŸ˜‰

    b45her
    Member

    but surely if they were faster the roadie companies would make them, afterall speed is king in the lycra world

    but surely if they were faster the roadie companies would make them, afterall speed is king in the lycra world

    Like 29ers and all the mtb companies making them?

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