Bicycle Mechanics - Single-Speed vs. Fixed Gear

I'm a newbie, trying to learn what I can ... what's the difference between a single speed and fixed gear and what are they each used for?

A single speed and fixed gear are very similar, but the single speed has a freewheel allowing you to coast the bike. A fixed, simply is a direct connection between your pedals and the rear wheel, so when the wheel is turning so are your feet. This means that a fixed gear can be built more simply, not only do you get to drop a freewheel but you can also drop your rear brake, or if you like drop both brakes. For someone getting one of these bikes, I would say this, there is almost no learning curve on the SS but on a FG you will have to train your brain.
Have Fun

Technically, a singlespeed is a bike that has only one gear ration (e.g., 39 chainring teeth and 16 teeth on the rear sprocket). A fixed-gear is a bike that does not coast - if the rear wheel is turning, so are the pedals. So, a singlespeed bike could be a single-speed fixed-gear bike or a fixed-gear bike with a freewheel - on the latter, you could coast. It's also possible to have a fixed-gear bike with multiple speeds - some people have done this with weird or modified internally-geared hubs, so you could have a bike with 3 gear ratios, but the gearing would be fixed if you couldn't coast while the bike was moving.

In practice, fixed-gear bikes are nearly always single-speed fixed-gear bikes, and so the term "singlespeed" is usually used to refer to a bike with one gear that has a freewheel so you can coast.

Fixed gear describes a single cog directly connected to the drive axle. When the rear wheel is turning, the pedals are turning; there's no freewheel.

Single speed describes a single cog driving the axle through a freewheel; you can "coast" with the pedals remaining in one position.

See Sheldon Brown's articles on fixed gear (http://sheldonbrown.com/fixed.html) and single speed (http://sheldonbrown.com/singlespeed.html).

Thanks, that helps a lot!

SS = coast
Fixed = no coast

Done.

If you are in your upper 50s a single speed means a bike you will ride and enjoy. Fixed gear means knee surgery. Roger

Fixed gear bikes are almost exclusively road bikes. Single speeds can be road or, more commonly, MTBs. Off road and trail terrain is too demanding and the obstacles to unpredictable to make riding a fixed gear safe. For example, you can't level your pedals and ride over a rock or log on a fixed gear but you can on a single speed.

Fixed gear bikes are almost exclusively road bikes. Single speeds can be road or, more commonly, MTBs. Off road and trail terrain is too demanding and the obstacles to unpredictable to make riding a fixed gear safe. For example, you can't level your pedals and ride over a rock or log on a fixed gear but you can on a single speed.

More's the challenge!

- Joel

Fixed gear bikes are almost exclusively road bikes. Single speeds can be road or, more commonly, MTBs. Off road and trail terrain is too demanding and the obstacles to unpredictable to make riding a fixed gear safe. For example, you can't level your pedals and ride over a rock or log on a fixed gear but you can on a single speed.


People build great fixed gears with MTBs for winter riders, a project for which I'm currently gearing up. And here in the city, nothing beats a single speed road bike conversion for pure urban riding fun. I've built three for various friends, and they love 'em more than any other bike they've ever had. If you live in a flat place, a singlespeed makes for a great, maintenance-free beater.

I think the categories are rapidly dissolving.

People build great fixed gears with MTBs for winter riders, a project for which I'm currently gearing up.
Ok, but they aren't going to use them for true mountain biking and, despite the bikes configuration, it's going to be used as a road bike.

Ok, but they aren't going to use them for true mountain biking and, despite the bikes configuration, it's going to be used as a road bike.

I'm building up a fixie mountain bike.

Know your abilities, know your trails, and leave your better thinking skills at the door.

If you are in your upper 50s a single speed means a bike you will ride and enjoy. Fixed gear means knee surgery. Roger

LOL, that's great.


Tim

LOL, that's great.


Tim
Tim, I got a good chuckle when I read it, too. Good one, Roger. :D

Ok, but they aren't going to use them for true mountain biking and, despite the bikes configuration, it's going to be used as a road bike.

Fixed gear mountain biking is growing. Fast: http://www.63xc.com/

I'm starting to think about dropping a 16T track cog on the other side of my ENO...

If you are in your upper 50s a single speed means a bike you will ride and enjoy. Fixed gear means knee surgery. Roger

I don't get this at all--how does coasting save your knees?

Thanks, that helps a lot!
sharrison, here's one more important difference between fixed-gear and singlespeed bikes... from a mechanic's perspective :)

A singlespeed can use a standard freewheel or cassette hub with only one cog. A fixed-gear, however, normally requires a special hub. The hub (called a track or fixed-gear hub) looks almost like a freewheel hub, in that the cog screws on to it. However, there's also a second set of slightly smaller threads which are reverse-threaded to allow a lockring to be tightened against the cog:

http://sheldonbrown.com/harris/images/hub-white-eno.jpg
(image from Sheldon Brown's site)

The lockring is very important on a fixed gear bike: it prevents the cog from unscrewing when you "resist" the pedals to slow down (that is, you push the pedals as if you were pedaling backwards). In order to build a safe fixed-gear bike, you need to rebuild the rear wheel with a fixed-gear hub. That's why a fixed-gear conversion is a little more complicated than a singlespeed conversion.

in addition to the above post, if someone simply wants a taste of fixed gear, or wants to do it on the cheap, using a normal freewheel road hub can work. Use a threadlocker on the threads, mount a bottom bracket lockring over the top of the sprocket if there's space, and tighten it on lots and lots using the rotafixa method:

http://204.73.203.34/fisso/eng/schpignone.htm

I've done a couple of fixed gear bikes this way, including two of my own, and the sprocket has held up to skidding, resisting and all that. As ever, run at least a front brake.

- Joel

I think this whole lockring thing is overrated. If you run proper brake(s) and do not solely rely on your legs for stopping, you could do without a lockring as long as the cog is securely mounted. Many fixed roadies with brakes, and even trackies on the track, don't bother with lockrings.

I think this whole lockring thing is overrated. If you run proper brake(s) and do not solely rely on your legs for stopping, you could do without a lockring as long as the cog is securely mounted. Many fixed roadies with brakes, and even trackies on the track, don't bother with lockrings.
I've spun a cog free, which was a disquieting feeling though fortunately I always use a brake on my fixies... maybe I shouldn't have greased that cog so carefully before installing it :) As a result, I like to use a lockring. It costs about $8.

I guess I understand why people build converted fixies with freewheel hubs, because it makes the job a whole lot easier and cheaper, but I'd rather have the peace of mind of a proper track hub. Plus, high flange track hubs are sexy :p

My fixed-gear bike has a cobbled-together rear wheel that starts with a traditional road freewheel-using hub. I bought the 27" rear wheel from eBay, was advertised as a track hub with a 3/32" width cog JB-welded onto the threads. Turns out it was a poorly converted freewheel hub, with a 1/8" track cog JB welded on and then a bottom bracket lockring screwed on for insurance. I got most of my money back, but converted the spacing so that the wheel could be dished evenly, then trued and tensioned extremely carefully. I can't replace a broken spoke, at least on the drive side, so I've got compelling interest to have this wheel perfectly tensioned!

That all said, the wheel has given me no problems whatsoever. I've done some of my riding with just a front brake, now with both brakes, but I'm not the sort of fixed-gear rider who does skidding. JB weld can take whatever force I've applied in the reverse direction, apparently. Not the case if I'd greased the interface though.

I don't get this at all--how does coasting save your knees?

It doesn't, people just like to joke about it. You can say it's almost a myth.

it's not the coasting, it's the grinding up hills in a tall gear which is bad for the knees. It's VERY bad for the knees if you do it in a seated position, without getting full leg extension. Ouch. This isn't unique to fixed gears though, any bike overgeared for the hill will give this problem. Resistance braking or skidding is also a strain on the knees, but a good (is there any good technique for such a thing?) technique may help somewhat.

- Joel

You can get multi-geared fixed if you can locate an old and very rare Sturmey Archer ASC (http://www.sheldonbrown.com/asc.html) 3 speed hub. Not many people know about these but they are quite nifty.

I suppose they could, but they are indeed rare. One recently went for $500us on ebay rather quickly. You can get a multi-speed fixed by modifying other internal gear hubs. There was a recent thread on left hand drive modifications in which this came up.

- Joel

it's not the coasting, it's the grinding up hills in a tall gear which is bad for the knees. It's VERY bad for the knees if you do it in a seated position, without getting full leg extension. Ouch. This isn't unique to fixed gears though, any bike overgeared for the hill will give this problem. Resistance braking or skidding is also a strain on the knees, but a good (is there any good technique for such a thing?) technique may help somewhat.

- Joel

This is what I don't get--grinding up a hill is part of singlespeeding too. Fixed gears are substantially easier on the knees on the hills in my experience.

So, here's what I still don't get: what do folks use a fixed gear or a single speed for?

I don't get this at all--how does coasting save your knees?
There is a growing body of anecdotal evidence that pedaling backwards (or simply resisting forward pedal motion) in order to brake on a fixed gear, especially at speed and especially if you are older (like me), can blow your knees. If you've got brakes and use them, it's not an issue.

Brake pads are cheaper than knee replacements.

So, here's what I still don't get: what do folks use a fixed gear or a single speed for?

Making whipped meringue for pies?

Fixed gears help your cadence, so when you ride a geard freewheel bike, you maintain a constant pedalstroke regardless of hills or obstacles.

Asthetically they are the most beautiful and simple machines known to man.

Singlespeeds are great if you ride a bike everyday and want to minimize your maintainence. Less parts, less hassle.

Less Hasslehoff?

So, here's what I still don't get: what do folks use a fixed gear or a single speed for?

It was, and I guess continues to be traditional winter training for road racers. Pick a mild gear ratio to force a higher cadence. Also, the back pedaling for braking uses a new set of muscles, making it a very efficient workout. In my experience, it increases your power band, meaning you can spin higher cadences in the same gear. Transfer that to a geared bike and when the race picks up, you can spin faster in the same gear, then pop it into a bigger gear and go. It's hard to explain, but it's a definite advantage.

Urban riders, such as messengers and commuters, like fixies because they are simple to maintain and there are fewer bits to attract vandals and thieves.

And for all types of riders, there's the feeling of being more connected to the machine and road. Some peopel talk about the zen of fixed riding. If you want to go faster, pedal faster. If you want to go slower, pedal slower.

ON EDIT: braking, not breaking. Ughh.

I think this whole lockring thing is overrated. If you run proper brake(s) and do not solely rely on your legs for stopping, you could do without a lockring as long as the cog is securely mounted. Many fixed roadies with brakes, and even trackies on the track, don't bother with lockrings.
why not? lock rings aren't expensive,they dont weigh a ton, you can get them pretty easily, and they take away any risk of your cog spining off.

well the lockring itself isn't a hassle, but sourcing and building a lockring-capable hub into a wheel IS a hassle. It defeats a large part of the appeal of fixed conversions - cheap, simple and mechanically reliable bikes.

- Joel

why not? lock rings aren't expensive,they dont weigh a ton, you can get them pretty easily, and they take away any risk of your cog spining off.
I forgot to add earlier that this pretains mostly to conversion hubs where BB lockrings are essentially useless...

True, that track lockrings are cheap. My point was if you have them, use them. If you don't have them and are running at least a front brake, then no big deal not having them on....

So, here's what I still don't get: what do folks use a fixed gear or a single speed for?

Like the others say, less parts, less hassle. In very flat places (like Chicago), there is no need for multi-speeds. Switching to SS/fixed reduces maintenance work. Derailleurs can be a pain to maintain in winter.

When you ride fixed gear you learn to micro-control your speed by varying the pressure you put on the pedals, often unconsciously. This may sound trivial but I found that if I go back to riding freewheels nowadays the amount of control that brakes gave me was unsatisfactorily coarse compared to what I can do on a fixed gear.

Riding a fixed gear is also good training because it eliminates the unhealthy habit of coasting. After switching to fixed gear I almost never coast even when I'm riding my multispeed road bikes.

I forgot to add earlier that this pretains mostly to conversion hubs where BB lockrings are essentially useless...

True, that track lockrings are cheap. My point was if you have them, use them. If you don't have them and are running at least a front brake, then no big deal not having them on....

Yeah why bother having any safety devices on anything at all.

It's VERY bad for the knees if you do it in a seated position, without getting full leg extension. Ouch.

Um. I get full leg extension while seated. I think your seat must be too low. (ouch!)

Yeah why bother having any safety devices on anything at all.

I removed all safefy covers from my printing presses. I never had my finger caught between the rollers.

Um. I get full leg extension while seated. I think your seat must be too low. (ouch!)

You shouldn't be having full leg extension in your normal pedalling position.

You shouldn't be having full leg extension in your normal pedalling position.
Yeah, but you should get close to full leg extension at the bottom of your pedal stroke.
If your seat is low enough that you don't get close to full extension at the bottom of the pedal stroke, then your knee is probably bending more than necessary at the top of the pedal stroke, and knee bending much beyond 90 degrees while riding can be a cause of injury.

when I'm pushing hard in a tall gear, I want a FULL leg extension, not the almost full leg extension I get at a correct seat height. The almost full leg extension is the most comfortable and efficient position 95% of the time though. The difference is small, but noticeable. Also, when you lean forward out of the saddle, I believe you get more potential force onto the pedals by virtue of how much you can pull on the bars in the different position.

- Joel

I'm not sure what you mean by this. When I push down on the pedal my leg fully extends. It does not lock but it extends as much as it does on the forward stroke when I walk. If I roll the ball of my foot down a bit I can lock it.

As a general rule you should rarely stand on your bicycle: http://www.sheldonbrown.com/standing.html

EDIT: To be honest. You should not be "pushing hard in a high gear" either. I suppose if you're riding a single speed you don't have a choice. :P But most people I know with a SS put the gear in the 65 inch range and learn to spin if they want to go fast.

I presume that article is about the efficiency of standing vs sitting and if so I agree, standing is inefficient. But this is a discussion about fixed and single speed bikes, from which I'm drawing my references. Uphill sitting and "spinning" in a 70-80 inch gear is beyond the capacity of most of us. All we can do is call on the extra force we can exert by standing up, pulling on the bars and perhaps swinging the bike side to side a little. Inefficient, but the only way.

I shall have to take some photos to explain this. When I'm pedalling at a comfortable 80-100rpm cadence my leg doesn't reach full extension. Nor do the legs of pro cyclists - watch closely next time you see some footage. If for some reason I want to exert more pressure for a stroke or two without standing, I can drop the heel slightly at the bottom of the stroke to gain that extra 5mm of extension to get the most out of the stroke. I think, JordanB, you and I are agreeing but using different words. If I consider my leg "fully extended" then the knee joint has an angle of zero, not an angle of 2-5 degrees or whatever it is now (I'm not even trying to pretend to quantify this, that would be a long and dull process).

- Joel

Sheldon's biggest point there is the danger of standing because of the potential for mechanical trouble.

And this is a problem with SS too beause the hub can slip and the chain become untensioned and then suddenly come off of the sproket, I've had that happen to me before, luckly I was sitting on the saddle so the only thing that happened to me is that I got a bruise on the back of one of my legs where the (platform) pedal came around and struck it.

But standing does help you mash the pedals because you get to use your body weight instead of just the leg muscles to force them down. I really don't think leg extension has anything to do with it though. You also get to pull up on the handlebars.

well I don't ride bikes with unreliable drivetrains, and I keep my chain tension in check, so half of the article doesn't really apply to me :)

- Joel

I'm not sure what you mean by this. When I push down on the pedal my leg fully extends. It does not lock but it extends as much as it does on the forward stroke when I walk. If I roll the ball of my foot down a bit I can lock it.

As a general rule you should rarely stand on your bicycle: http://www.sheldonbrown.com/standing.html

EDIT: To be honest. You should not be "pushing hard in a high gear" either. I suppose if you're riding a single speed you don't have a choice. :P But most people I know with a SS put the gear in the 65 inch range and learn to spin if they want to go fast.

Pushing a hard gear up a hill is a fine training technique. I often do hill repeats in my 53-12 on 2-minute climbs at about a 5% grade. Very slow cadence (50?), and it's great for building strength. I do them seated. Slide back in the saddle (more leg extension), drop the elbows, straight writsts, and pull hard on the bar tops when my legs are pushing the bike out from under me.

Standing is also a fine thing to do. I know people rip on it, but standing changes muscle groups, allowing you to recover briefly. It's a more powerful, but less efficient position. Stand on steep sections of long climbs and during sprints.

I also do out-of-saddle hill repeats to develop those muscles.