wheelbuilding with arup

Are you thinking of converting to fixed?

fixed gear questions

Here are some of the questions about fixed gear riding that I get asked time and time again. These are mainly about converting your existing bike to fixed. If you have other questions, then of course feel free to ask.

Do I have the right frame?

It is possible to convert any type of frame to fixed gear, but the job is much easier if the frame has horizontal or near horizontal dropouts. The dropouts are where the rear wheel axles fit into the frame. This is so that the chain can be tensioned correctly.

What sort of hub do I need?

You will need a hub that allows you to fit a fixed sprocket. These are often called fixed hubs or track hubs. Sometimes you have to buy a pair (front and rear) or you just buy the rear hub only. That's all you really need if you want to convert your rear wheel.

There are also double fixed hubs which allow you fit a sprocket on each side so that in effect you would have two gears. You can then change gear by removing the wheel and turning it over.

The other one you could get is called a “flip–flop” hub. This means that you have a fixed sprocket on one side and a freewheel on the other. Again, to change from one to the other you would remove the wheel and turn it around.

What size hub do I need?

This depends on your OLN or overlock nut distance. That means the space between your rear dropouts. This is typically 120mm, 126mm, 130mm or 135mm. It is best to get the correct fit, however a shorter hub can be fitted in a larger spacing using spacer washers. This can effect your chainline.

How do I choose the right gear ratio?

This is easier than you would think. On your geared bike have a look at your cassette or block. Which cogs or gears are the most worn? Do the same on the front chainrings. The ones with the most wear are the ones that you use the most. That's a good starting point. That will narrow it down to a few choices.

What is chainline?

The chainring and the rear sprocket need to be on the same plane. You can probably get away with a few mm and geared bikes do more than that. On a fixed gear bike it is imperative for the chainline to be accurate. For reasons of safety and efficiency.

If the chainline is not good then there is increased risk that the chain could derail which could cause an accident. If the chainline is only slightly inaccurate then the chain would wear more quickly and would also cause the chainring and sprocket to wear faster. Less of your efforts would also be transferred to motion.

How do I set the chain tension?

Think of it rather like tuning a stringed instrument. It must neither be too loose nor too tight. I find that the best way to do it is to make it really tight and then slacken it off by up to 3%. There should be a perceptible movement of the pedals when you are stationary, but only just.

It should feel smooth and easy to rotate as though the chain is loose. But if it is too loose then it could come off. Too tight and it starts to bind and makes it very difficult to turn. Too tight also causes faster wear.

Do I need a lock ring?

For safety's sake yes. I have read reports of sprockets working loose especially if you use your legs to slow down or pull skids. My first fix had spacers and no lock ring and that was fine. Your choice, your risk.

What’s better ³⁄32 or ¹⁄8?

That’s the thickness or width of the chain and components that fit into them. Often referred to as “pitch”. Is one better than the other? ¹⁄8 is supposed to give a slightly better efficiency but is also reported to be a bit noisier. You can get away with a less than accurate chainline with ³⁄32 which you can’t with ¹⁄8.

Aesthetically ¹⁄8 can give a chunckier or meatier look to your bike which you may find pleasing. ¹⁄8 parts tend to be a bit more expensive too. I would say it’s a matter of taste.

How can I prepare for riding fixed?

If you are about to convert your bike and having your wheel built then here are a few exercises that you can do.

On your geared bike, find the ratio that you want to use and use only that gear. Try it for a couple of weeks. Notice where you naturally or habitually freewheel and consciously keep pedalling. Going down hill, approaching junctions or traffic lights and going round bends. And no changing down when you go up hills either!

When you have your new fix but haven’t ridden before a few exercises should help you get the hang of it before you start commuting.

Find a quietish stretch of road and practise clipping in and out. Try the stopping and starting. Have a go at slowing the bike down with your legs. You just need to relax your legs. Do it when you are going slowly until your knees are up to it. Try going really slow without stopping. And just generally speeding up and slowing down. Try a few sudden stops as well, using the brake of course.

Work on pulling up with your legs rather than focusing on pushing down on the pedals. This will lead to a smoother pedalling action and set you up for spinning fast when you go down hills and find an open stretch of road. (Not likely in London, but does happen at night.)