Fixed Gear for the Road (Part 2)
erailer bikes can work fairly well even with the chain running at a considerable angle, but this should not be done with a fixed-gear setup. It is quite important to get the chain line just right.
I usually check the chainline by installing the hub in the bike, with no chain installed. By placing my head just in front of the chain wheel, I can sight along the chainwheel and see back to the rear hub, to see if the chainwheel lines up exactly with the rear sprocket. If it doesn't, I re-arrange spacers or change the bottom bracket axle as necessary.
Usually, on a bike that came with double chainwheels, the inner chainwheel will be more in line with the rear sprocket. If you wish to make the bike a pure fixed gear, you can buy a set of shorter "stack bolts" (the 5 bolts that hold the chainwheel(s) to the crank spider). You may find it easier to locate these in a shop that deals in BMX bikes.
Chain Tension
he chain tension on a fixed gear is quite critical, and is regulated by moving the rear axle back and forth in the fork ends. If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, which is quite dangerous on a fixed gear.
Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chain ring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.
This takes a little bit of your hands learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.
Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. My standard pattern is to start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt.
Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible.
ear choice for a fixed gear is a very personal matter, and will depend on your style, your goals, and the terrain you ride in.
I live in New England, with small rolling hills. For a bike with normal road-type wheels and 165 mm cranks, I find that 42/15 suits me best. This gives a gain ratio of 5.77 (75.6" / 6.05 m gear). This is low enough that I can make it up the hills where I usually ride, but high enough that I can go reasonably fast down the other side.
Racers using a fixed gear for winter training usually like a considerably lower gear to improve their spinning technique.
Those who live in the flatlands will likely prefer something substantially higher. When I visit my sister in Illinois, I flip my wheel around so that I can use the 42/14, a gain ratio of 6.18 (81.0" / 6.48 m).
Time trialists often prefer something higher yet. (Many British time-trialists prefer a fixed gear for these road events.) Beryl Burton, probably the greatest time-trialist in history, used a fixed gear almost exclusively. If I recall correctly, she usually ran a 52/14 or 52/13!
he most important characteristic to look for in choosing pedals for a fixed-gear bike is good ground clearance. Although I often ride with clipless pedals on multi-speed bikes, I usually ride a fixed gear with toe clips and shoes without cleats.
A large part of the reason for this is that I can effectively "change gears" depending on how far into the toe clips I stick my feet. For climbing or accelerating, I usually stick my toes all the way in. This gives me more effective leg extension, and lets me push harder on the pedals. For cruising, I pull my feet back a bit, and for really fast spinning I pull back even further. Doing this has somewhat the same effect as lowering my saddle a bit, and makes it easier to spin at high rpms.
I fit two toe straps to each pedal, partly because they help keep my feet in better alignment (since I don't use cleats) and partly for safety. Toe straps can get highly stressed on a fixed-gear bicycle, and if they break, unpleasant consequences may ensue.
Mounting Technique
iding a fixed-gear bicycle requires proper mounting technique. Many cyclists have bad mounting habits, such as swinging the leg over on-the-fly, or starting up by shuffling their feet against the pavement. These techniques work even worse on a fixed-gear bicycle than they do on a freewheel machine.
Getting your first pedal into the proper forward-and-up position is a bit trickier with a fixed gear, since you can't just spin the pedals backward. The trick is to put your foot on the pedal, then lift the rear end of the bicycle up so that you can turn the pedals.
I used to lift the bicycle up by the edge of the saddle, but I damaged a Brooks Pro that way--the rivets that held the leather top to the saddle frame pulled out from being stressed in this un-anticipated direction!
My friend Osman Isvan recently taught me a much better technique: The trick is to straddle the bike, put one foot on a pedal, lock up the front brake and press forward on the handlebars. The forward force on the bars will lift the rear wheel enough to let you revolve the pedal to where you want it.
Dismount Technique
ou can dismount in the normal manner from a fixed-gear bicycle, but advanced fixed-gear riders might enjoy learning a special, very cool-looking dismount that can only be done from a fixed gear:
Instead of getting off to the side of the bicycle, the fixed-gear rider can go straight off the back. This technique works best if you ride with clips & straps, but if you are really proficient in disengaging from clipless pedals, try it at your own risk.
As the bicycle slows to near walking speed, disengage your left foot, then wait for the right pedal to get to the bottom of its circle. As the right pedal starts to rise, straighten your right leg and let the motion of the pedal lift you up. Let go of the handlebars, let the saddle move forward between your legs, and put your left foot on the ground. As the bike goes ahead, grab it by the saddle.
It takes a bit of courage to try this, but it is actually very easy to do. It is also extremely impressive to watch. When executed properly, it is very smooth, and you can go from riding to walking in a single fluid motion, without ever coming to a stop.
Braking
ome fixed-gear riders ride on the road without brakes. This is a bad idea. I know, I've tried it. If you do it, and have any sense of self-preservation at all, it will cause you to go much slower than you otherwise could, everytime you go through an intersection, or pass a driveway. The need for constant extra vigilance takes a great deal of the fun out of cycling.
You really should have a front brake. A front brake, all by itself, will stop a bicycle as fast as it is possible to stop. This is true because when you are applying the front brake to the maximum, there is no weight on the rear wheel, so it has no traction.
One of the wonderful things about fixed-gear riding is that the direct feel you get for rear-wheel traction teaches you exactly how hard you can apply the front brake without quite lifting the wheel off of the ground.
This is a very valuable lesson for any cyclist who likes to go fast; it could save your life.
There is really no need for a rear brake on a fixed-gear bicycle. By applying back-pressure on the pedals, you can supply all the braking that the rear wheel really needs. In fact, it is fairly easy to lock up the rear wheel and make it skid, unless you are running a rather high gear.
Some fixed-gear fans make a point of not using their brake except in an emergency. I am not sure that this is a good idea. Heavy duty resisting is widely reputed to be bad for your legs, and to be counterproductive for building up muscles and coordination for forward pedaling.
This is a lot like car drivers who use their transmission and clutch to slow down, even though the car has a special set of parts made for the exact purpose of slowing down. Brake shoes are cheaper to replace when they wear out than clutches are.
Fixed gear dangers:
should warn you that there are three dangers related to fixed-gear bicycles that are not a problem with freewheel bicycles. Used and maintained properly, fixed gear bicycles can be as safe as any, but you should be aware of the three danger areas:
Pedal Strike
t is never a good thing to strike your pedal on the ground while cornering tightly. On a freewheel bike, you can coast though the corners with your pedals horizontal, thus avoiding any chance of striking. On a fixed-gear machine, you don't have this option.
If you do bang a pedal on a fixed gear, the pedal can lift the rear wheel off the road, and down you will go. This has never happened to me, but it is something to bear in mind.
How much of a problem this is will depend on your bottom bracket height, crank length, and the design of your pedals.
Most of my fixed-gear bikes have 165 mm cranks,which give a bit more ground clearance than the 170 mm's usually used on road bikes. I also make a point of using pedals that don't stick out too far.
Derailment and Wheel Lock
hrowing a chain on a freewheel bike is no big deal, but it can be very dangerous on with a fixed gear. If the chain comes off of the chainwheel, it can get hung up or even loop around the rear sprocket, and can cause the wheel to lock up. If this happens while you are leaned over in a turn, you will almost certainly crash.
This is prevented by making sure that your chainline is straight, and that your chain is adequately tight.
Crushing Fingers, Trousers, Shoelaces
he other danger of fixed-gear bicycles is at its greatest when the bike is in a repair stand. If you hand-pedal it and then accidentally have a finger an article of clothing come into contact with the chain or a sprocket, the momentum of the wheel will keep the drive train rolling. You can lose a finger that way.
Likewise, when riding, if you are wearing floppy pants, or have an un-tied shoelace, you may get your clothing caught in the drive train. On a freewheel bike, this it is a minor inconvenience. You have to coast, then pedal backward to release your clothing. The worst that will happen is that your clothing will get soiled.
With a fixed gear, you have no such option. If you catch a shoelace, it will get torn off or your shoe. If you catch a trouser leg, you can really get hurt.
It is my fervent hope that this article will persuade some of those who read it to give a try to fixed-gear riding, may you learn to enjoy it as much as I do (and I have 11 fixed-gear bikes!)
If you do,
send me a message! I'm collecting testimonials from happy fixed-gear converts, you can read some here!
More Fixed Gear Pages on This Site:
since January 3, 1996
Updated Sunday, May 7, 2000 3:45 PMURL: http://sheldonbrown.com/fixedb.html