Bike-a-Boo

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?

Andreasaway

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

TallRider

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.

Scooper

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 and single speed.

Bike-a-Boo

Thanks, that helps a lot!

operator

SS = coast
Fixed = no coast

Done.

rhenning

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

HillRider

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.

tomacropod

More's the challenge!

- Joel

peripatetic

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.

HillRider

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.

Eatadonut

I'm building up a fixie mountain bike.

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

cs1

LOL, that's great.


Tim

Scooper

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

waterrockets 

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

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

seely

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

moxfyre

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:


(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.

tomacropod

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:

https://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

roadfix

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.

moxfyre

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

TallRider

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.

operator

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

tomacropod

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

MichaelW

You can get multi-geared fixed if you can locate an old and very rare Sturmey Archer ASC 3 speed hub. Not many people know about these but they are quite nifty.

tomacropod

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