Today I decided to do the bike courier thing and run some errands on the fixie. The route was as flat as it gets around here and I'm taking it easy this week training so it was an easy choice. Stopped by my lbs and dropped off a bunch o stuff for the swap meet, then headed to the twp rec office to purchase pool passes, then back home and stop along the way at Sugar Moma's to get some good Guatemalan beans. As I was cruising along, almost effortlessly, I realized that on the fixie, once you get going and it's afairly flat route, you can ride almost forever.

Generally, your butt starts to hurt before your legs give out.

I noticed this too, when I went on my first fixie run. I went down the street to make sure everything was in order and working properly on my new build, and I just kept going. I just didn't want to stop. The momentum almost propels you up hills and across the flats. 5 miles later I decided to turn around and head home since I was wearing jeans and no helmet.

The momentum almost propels you up hills and across the flats. 5 miles later

Don't get me wrong; I love riding FG, too. But it sure don't propel you anywhere. It's the good feeling and the fun that make you want to keep going. On anything but a dead flat route with the perfect gear, the fixie will make you work harder than a multi-geared bike would.

That's a good thing, when that's what you're in the mood for.

On anything but a dead flat route with the perfect gear, the fixie will make you work harder than a multi-geared bike would.

I have to disagree with you here. I do think the momentum of the drivetrain contributes to the ride. Try climbing with a single speed with the same gearing. You will still mash the pedals, but you don't get the benefit of your momentum on the upstroke like you do on a fixed gear. Everytime you stop and pause...even for a second....you lose momentum.

Fixie vs. geared is a different story. Yes, you can ride faster/farther over varied terrain on a geared bike, but it's not simply because you have a freewheel, it's because you have multiple gears.

Speaking of riding all day, all I know is it is a hell of a lot more tiring (but not necessarily harder) to do a century or double century ride on a fixed gear than it is on a geared bike, hills or no hills......

I have to disagree with you here. I do think the momentum of the drivetrain contributes to the ride. Try climbing with a single speed with the same gearing. You will still mash the pedals, but you don't get the benefit of your momentum on the upstroke like you do on a fixed gear. Everytime you stop and pause...even for a second....you lose momentum.

Fixie vs. geared is a different story. Yes, you can ride faster/farther over varied terrain on a geared bike, but it's not simply because you have a freewheel, it's because you have multiple gears.

You don't have any more momentum on a fixed than you do on a freewheeling bike. The only difference is some small part of the momentum on the FG is being used to keep the crank turning. If you let the "upstroke momentum" lift your leg (instead of using your muscles the way you have to on the freewheeler), that's got to cost you something in the speed of the bike. There's no free lunch in physics.

I agree it FEELS smoother, and that's a good thing. I like riding fixed, and we agree on that, too. But it's not a perpetual motion machine.

On a climb the momentum is a pretty insignificant part of the equation anyway. Fixed or free, if you don't push you quickly slow and stop.

I also agree that gear selection is much the larger factor in terms of the efficiency difference between fixed and multi-geared bikes.

I never took physics, and I knew I'd get called out on my use of "momentum". :)
You're right, there isn't a whole lot of benefit (maybe none at all) on climbs, especially steep ones. But when it comes to small climbs and rollers, I do "feel" like I'm being propelled by the forward motion of the bike acting on the drivetrain, and ultimately contributing - ever so slightly - to my muscular efforts at the pedals. Much more apparent (to me) on a fixie than on a freewheeled bike.

Maybe it's perpetual motion, maybe it's the smoother cadence, maybe it's magic....or it could just be that fixed gear bikes are a blast to ride.

I never took physics, and I knew I'd get called out on my use of "momentum". :)
You're right, there isn't a whole lot of benefit (maybe none at all) on climbs, especially steep ones. But when it comes to small climbs and rollers, I do "feel" like I'm being propelled by the forward motion of the bike acting on the drivetrain, and ultimately contributing - ever so slightly - to my muscular efforts at the pedals. Much more apparent (to me) on a fixie than on a freewheeled bike.

Maybe it's perpetual motion, maybe it's the smoother cadence, maybe it's magic....or it could just be that fixed gear bikes are a blast to ride.

No quarrel on that last statement :-)