Help me understand fixies

Discussion in 'The Bike Cafe' started by kdelong, Jul 31, 2009.

  1. alienator

    alienator Well-Known Member

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    I just saw a piccie of a Colnago Master that was turned into a fixie. I cried.
     


  2. garage sale GT

    garage sale GT New Member

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    I think singlespeed and fixed are more popular in urban areas because there's more occasion for shifting along with more stuff occupying your attention. Cheap bikes go out of order, 1970s bikes have to be shifted by letting go of the controls. Conversions also often feature better brake levers than old tenspeeds.

    I still like taking a singlespeed out through bike paths or forest preserve roads where you don't have to shift often and where there's less cars, pedestrians, curbs, potholes, etc occupying your attention. It's a nice bike to ride.

    Sturmey ads for the fixed 3 speed used to read "the hub that keeps you pedaling," complete with pictures of a rider bundled up for winter. Maybe the idea that they're better for training comes in part from the idea that coasting in cold weather is bad for muscles.

    As for the trend, who knows.
     
  3. ::dom::

    ::dom:: New Member

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    LOL... but it's hard to pose when you're actually cycling :)
     
  4. ::dom::

    ::dom:: New Member

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    Ride one.
     
  5. kdelong

    kdelong Well-Known Member

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    I have test ridden eleven fixies (one of my own that I breifly and only temporarily converted and changed back) and single speeds since my original post and I still don't see where they are superior or even close to equal to any of my multi-speed bikes. It is just my opinion, and that is why I asked the question in the first place. A lot of people have replied "Ride one" or something similar like you did, and after riding the borrowed bikes, I still don't see the allure of one speed bikes. I had fun converting my Univega, but the ride was no different than if I just left it in one gear, so I restored it to the 8 speed that it was before my experiment. Therefore I agree that it is just a passing fad, but I still hate seeing formerly great frames falling victim to the Fixie Cutting Wheel.
     
  6. Cully_J

    Cully_J New Member

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    Fixies are extremely functional bikes for the city. Their difficulty for the newbie makes them virtually theft-resistant.

    This New York Times article does a great job explaining their attractiveness:
    Unstoppable - New York Times
     
  7. JaredSanders

    JaredSanders New Member

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    Haha, my point exactly lol. But that would only apply to a SS, with a FG, it's actually a little easier to go uphill (at least a moderate/ easy gradient) because your downward pedalstroke is much more efficient, instead of mashing the pedals with gears or a SS.
     
  8. alienator

    alienator Well-Known Member

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    This is absolutely false. There is nothing in physics that would indicate that a fixie is much more efficient going uphill. A bicycle drivetrain is already 98% efficient. Any energy loss caused by two derailleurs is minimal, and you'd need laboratory measurements to see any difference. Changes in chainline on a multiple gear bike also create miniscule losses of energy. Any differences you feel are in your head and are the result of personal bias, not anything in the drivetrain.
     
  9. JaredSanders

    JaredSanders New Member

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    I don't think I meant "much" more efficient, sorry. And if you do an experiment, basic physics, the more pullies, the less effiecient, even if there is 1 pully. I guess I should have said that it felt a little easier for ME, going up small hills.
     
  10. alienator

    alienator Well-Known Member

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    Yeah, I understand the physics. That's why I say the difference would be essentially meaningless, and a rider could not discern the difference from any of the "noise" in the ride. The differences between the two scenarios is not just a matter of "more pullies." That's only one factor, and there the real cause is friction. Given that, the friction of additional pullies--which don't wrap to the extent of chainrings and cogs--is lessened by using bigger cogs and chainrings, something easily accomplished on a mult-gear bike. Again, presto chango, things are more efficient.

    I don't think you completely understand the differences in magnitude we're talking about. We're talking about differences that could be lost in the noise of a lab measurement. Let's fact it: the human body has been shown to be a crap detector because it can't reliably discern such low level inputs. Moreover, the human sensor is polluted my emotional/mental bias.

    What you feel is what you want to feel.
     
  11. BicyclingGuitar

    BicyclingGuitar New Member

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    While my 1977 Schwinn Sportabout is a ten-speed, I keep it in first gear all the time because I play guitar as I ride and don't want to go too fast. The bicycle still has all ten speeds available even if I never use any other than the lowest.
     
  12. garage sale GT

    garage sale GT New Member

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    I think you seem to go uphill faster and easier with singlespeed/fg because the gear which is the most comfortable is not necessarily the best. I can't believe it wouldn't feel exactly the same if I climbed the small hills around here in a 42/17 on a road bike or MTB with 27-30 speeds vs using a fg.

    There is a pleasantness to them, though. I don't know what it is. Provided you are strong enough to handle the local hills and fast enough to spin at a decent speed, they are great bikes to ride. If you don't like it, or live in the rockies, then don't get one.
     
  13. oldbobcat

    oldbobcat Well-Known Member

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    I beg to differ. The lack of a freewheel lets the flywheel effect of the rear wheel push the cranks through the dead spots in our pedal strokes. And we all have those.
     
  14. alienator

    alienator Well-Known Member

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    Uhm, you've got that wrong. The angular momentum present in a fixie is the exact same angular momentum present in a multi-gear bike. It has to be; otherwise Newton's mechanics would be all uipset. Given the same gear ratio, the effort to turn the cranks 'round on a fixie is exactly what it is on a multi-gear bike. The force diagram is the same.

    If you don't believe me, read all the micro acceleration threads all over the internet. In this thread, Mark McM presents an excellent mathematical model of a bike in motion. It applies equally to multi-geared bikes and fixies. It's a very elegant analysis he put together. His partial differential equation proves invalid your supposition.
     
  15. oldbobcat

    oldbobcat Well-Known Member

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    I should have said the flywheel effect of the wheel plus the ability of the chain on the fixie to transfer the energy from the momentum of the mass of bike plus rider directly to the cranks.

    Mark McM's analysis uses the straight-line momentum of the mass of the bike and rider and the rotating mass of the wheels to calculate the net loss of average velocity caused by oscillations in momentary speed.

    My intuitive analysis says that some of the mass of the bike and rider driving the chain through the stroke has an effect similar to increasing the rotating mass, further reducing fluctuations in velocity. Anyway, this is the what my legs are telling me when I pedal home, upwind and slightly uphill, at the end of a fixie workout.
     
  16. alienator

    alienator Well-Known Member

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    The chain doesn't transfer any power when power isn't applied to it. It can't, because it is human powered! When coasting all that happens is that energy stored in the drivetrain is drained by chain friction, friction in the hub, and friction in the bottom bracket. This is exactly the same case with a geared bike. Let me say this again: the flywheel effect is an energy STORAGE thing. On a bike, flywheel effect is NOT providing power.

    Mark McM's analysis applies because it is the general equation of motion, for a bike, along one axis. His analysis can easily be extended to three dimensions.

    There's no way around the fact that the fixie isn't using a benefit not available to a geared bike. In terms of acceleration and energy, the defining equations are the same.
     
  17. JTE83

    JTE83 Member

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    I bought a 2008 Specialized Langster New York Edition Singlespeed / Fixie bike and I put a Mity 8 computer on it. After riding it top speed is around 21 mph so single speeds suck for speed because you can't gear higher. And then they are slow to accelerate. I guess the attraction for them is that they have less parts to strip and steal, but after my experiment riding a single speed, - I say they SUCK! I'll take a geared road bike anytime over a singlespeed / fixie, but these bikes give you a workout!
     
  18. swampy1970

    swampy1970 Well-Known Member

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    42x16 at 21mph is no more than 110rpm...
    ... the verdict again is unanimous.You SUCK.

    42x16 should accelerate like a rocket. Stop blaming the bike.

    You bought a nearly new bike that retails for over $700 for an experiment? Did mommy pay for it?
     
  19. Cully_J

    Cully_J New Member

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    One of the beautiful thing about riding fixed is that you can find an awesome bike that's cheap because of messed up gears, and make it rideable again...
     
  20. alienator

    alienator Well-Known Member

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    The real problem was that he couldn't do rad tricks and jumps with it to impress the little boys at the skate park.
     
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